Positive end-expiratory pressure at minimal respiratory elastance represents the best compromise between mechanical stress and lung aeration in oleic acid induced lung injury.

PubMed

Carvalho, Alysson Roncally S; Jandre, Frederico C; Pino, Alexandre V; Bozza, Fernando A; Salluh, Jorge; Rodrigues, Rosana; Ascoli, Fabio O; Giannella-Neto, Antonio

2007-01-01

Protective ventilatory strategies have been applied to prevent ventilator-induced lung injury in patients with acute lung injury (ALI). However, adjustment of positive end-expiratory pressure (PEEP) to avoid alveolar de-recruitment and hyperinflation remains difficult. An alternative is to set the PEEP based on minimizing respiratory system elastance (Ers) by titrating PEEP. In the present study we evaluate the distribution of lung aeration (assessed using computed tomography scanning) and the behaviour of Ers in a porcine model of ALI, during a descending PEEP titration manoeuvre with a protective low tidal volume. PEEP titration (from 26 to 0 cmH2O, with a tidal volume of 6 to 7 ml/kg) was performed, following a recruitment manoeuvre. At each PEEP, helical computed tomography scans of juxta-diaphragmatic parts of the lower lobes were obtained during end-expiratory and end-inspiratory pauses in six piglets with ALI induced by oleic acid. The distribution of the lung compartments (hyperinflated, normally aerated, poorly aerated and non-aerated areas) was determined and the Ers was estimated on a breath-by-breath basis from the equation of motion of the respiratory system using the least-squares method. Progressive reduction in PEEP from 26 cmH2O to the PEEP at which the minimum Ers was observed improved poorly aerated areas, with a proportional reduction in hyperinflated areas. Also, the distribution of normally aerated areas remained steady over this interval, with no changes in non-aerated areas. The PEEP at which minimal Ers occurred corresponded to the greatest amount of normally aerated areas, with lesser hyperinflated, and poorly and non-aerated areas. Levels of PEEP below that at which minimal Ers was observed increased poorly and non-aerated areas, with concomitant reductions in normally inflated and hyperinflated areas. The PEEP at which minimal Ers occurred, obtained by descending PEEP titration with a protective low tidal volume, corresponded to the greatest amount of normally aerated areas, with lesser collapsed and hyperinflated areas. The institution of high levels of PEEP reduced poorly aerated areas but enlarged hyperinflated ones. Reduction in PEEP consistently enhanced poorly or non-aerated areas as well as tidal re-aeration. Hence, monitoring respiratory mechanics during a PEEP titration procedure may be a useful adjunct to optimize lung aeration.

Hydraulic characterization and optimization of total nitrogen removal in an aerated vertical subsurface flow treatment wetland.

PubMed

Boog, Johannes; Nivala, Jaime; Aubron, Thomas; Wallace, Scott; van Afferden, Manfred; Müller, Roland Arno

2014-06-01

In this study, a side-by-side comparison of two pilot-scale vertical subsurface flow constructed wetlands (6.2 m(2)×0.85 m, q(i)=95 L/m(2) d, τ(n)=3.5 d) handling primary treated domestic sewage was conducted. One system (VA-i) was set to intermittent aeration while the other was aerated continuously (VAp-c). Intermittent aeration was provided to VA-i in an 8 h on/4 h off pattern. The intermittently aerated wetland, VA-i, was observed to have 70% less nitrate nitrogen mass outflow than the continuously aerated wetland, VAp-c. Intermittent aeration was shown to increase treatment performance for TN while saving 33% of running energy cost for aeration. Parallel tracer experiments in the two wetlands showed hydraulic characteristics similar to one Continuously Stirred Tank Reactor (CSTR). Intermittent aeration did not significantly affect the hydraulic functioning of the system. Hydraulic efficiencies were 78% for VAp-c and 76% for VA-i. Copyright © 2014 Elsevier Ltd. All rights reserved.

Enhanced nitrogen removal of low C/N domestic wastewater using a biochar-amended aerated vertical flow constructed wetland.

PubMed

Zhou, Xu; Wang, Xuezhen; Zhang, Hai; Wu, Haiming

2017-10-01

Recently, vertical flow constructed wetlands (VFCWs) with intermittent aeration have been proven as an efficient technology to enhance removal efficiency of organics and nitrogen for wastewater treatment. However, the low denitrification effect in VFCWs was a problem for treating low carbon source wastewater. In this study, intermittent aeration and biochar, produced by biomass pyrolysis, was used to promote the nitrogen removal in VFCWs for low C/N domestic wastewater. Four systems, including non-aerated with non-biochar VFCW, non-aerated with biochar VFCW, aerated with non-biochar VFCW and aerated with biochar VFCW, were conducted for comparing their treatment performances. The results showed that much higher removal of COD (94.9%), NH 4 + -N (99.1%), TN (52.7%) and lower N 2 O emission (60.54μg·m -2 ·h -1 ) was obtained in aerated VFCW with biochar addition. The results suggested that adding biochar to intermittent aerated VFCWs could be an effective and appropriate strategy for low C/N wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enhancement of ultrasonic disintegration of sewage sludge by aeration.

PubMed

Zhao, He; Zhang, Panyue; Zhang, Guangming; Cheng, Rong

2016-04-01

Sonication is an effective way for sludge disintegration, which can significantly improve the efficiency of anaerobic digestion to reduce and recycle use of sludge. But high energy consumption limits the wide application of sonication. In order to improve ultrasonic sludge disintegration efficiency and reduce energy consumption, aeration was introduced. Results showed that sludge disintegration efficiency was improved significantly by combining aeration with ultrasound. The aeration flow rate, gas bubble size, ultrasonic density and aeration timing had impacts on sludge disintegration efficiency. Aeration that used in later stage of ultrasonic irradiation with low aeration flow rate, small gas bubbles significantly improved ultrasonic disintegration sludge efficiency. At the optimal conditions of 0.4 W/mL ultrasonic irradiation density, 30 mL/min of aeration flow rate, 5 min of aeration in later stage and small gas bubbles, ultrasonic sludge disintegration efficiency was increased by 45% and one third of ultrasonic energy was saved. This approach will greatly benefit the application of ultrasonic sludge disintegration and strongly promote the treatment and recycle of wastewater sludge. Copyright © 2015. Published by Elsevier B.V.

Experimental investigations of aeration efficiency in high-head gated circular conduits.

PubMed

Cihat Tuna, M; Ozkan, Fahri; Baylar, Ahmet

2014-01-01

The primary purpose of water aeration is to increase the oxygen saturation of the water. This can be achieved by using hydraulic structures because of substantial air bubble entrainment at these structures. Closed conduit aeration is a particular instance of this. While there has been a great deal of research on air-demand ratio within closed conduit, very little research has specifically addressed aeration efficiency of closed conduit. In the present work an experimental study was conducted to investigate the aeration efficiency of high-head gated circular conduits. Results showed that high-head gated circular conduits were effective for oxygen transfer. The effects of Froude number and ratio of the water cross-sectional flow area to the conduit cross-sectional area on aeration efficiency were particularly significant, whereas the effect of conduit length was only moderate. Further, a design formula for the aeration efficiency was presented relating the aeration efficiency to ratio of water cross-sectional flow area to conduit cross-sectional area and Froude number. The obtained results will be useful in future modeling processes and aid the practicing engineer in predicting aeration efficiency for design purposes.

Surfactant effects on alpha factors in full-scale wastewater aeration systems.

PubMed

Rosso, D; Larson, L E; Stenstrom, M K

2006-01-01

Aeration is an essential process in the majority of wastewater treatment processes, and accounts for the largest fraction of plant energy costs. Aeration systems can achieve wastewater oxygenation by shearing the surface (surface aerators) or releasing bubbles at the bottom of the tank (coarse- or fine-bubble aerators). Surfactants accumulate on gas-liquid interfaces and reduce mass transfer rates. This reduction in general is larger for fine-bubble aerators. This study was conducted to evaluate mass transfer effects on the characterization and specification of aeration systems in clean and process water conditions. Tests at different interfacial turbulence regimes were analysed, showing higher gas transfer depression for lower turbulence regimes. Higher turbulence regimes can offset contamination effects, at the expense of operating efficiency. This phenomenon is characteristic of surface aerators and coarse bubble diffusers and is here discussed. The results explain the variability of alpha factors measured at small scale, due to uncontrolled energy density. Results are also reported in dimensionless empirical correlations that describe mass transfer as a function of physiochemical and geometrical characteristics of the aeration process.

[Novel resources utilization technique for rural domestic refuse].

PubMed

Qiu, Cai-Di; He, Ruo; Chen, Song-Mei; Lou, Bin; Shen, Dong-Sheng

2009-03-15

In order to speed up rural domestic refuse resources utilization, intermittent aeration and continuous aeration were applied to treat rural domestic refuse after anaerobic fermentation. Three kinds of refuse were selected on base of fermentative age, i.e. three months, five months and seven months. Results showed that aeration could remove water and organic materials of the refuse effectively. Points of view on aeration, continuous aeration was better than intermittent aeration, and on the other side, water removal rate increased with ventilation and decreased with fermentative age in the condition of intermittent aeration. On organic materials removal point, it was affected by fermentative age significantly, i. e. increase of fermentative age could resulted in decrease in the removal efficiency. In conclusion, intermittent aeration of 0.06 m3/(min x m3) was considered to be feasible for treatment. The water removal efficiency of three months, five months and seven months fermentative age refuse could be up to 49.1%, 45.3% and 44.0%, and organic compound removal efficiency was 41.9%, 24.8% and 13.1%, respectively, after intermittent aeration for 21 d. Moreover, concentrated effect was presented on major nutrient ingredients, such as total nitrogen, phosphorus, and potassium during the aeration, which realized for resources utilization.

Impact of post-infiltration soil aeration at different growth stages of sub-surface trickle-irrigated tomato plants

NASA Astrophysics Data System (ADS)

Li, Yuan; Jia, Zong-xia; Niu, Wen-Quan; Wang, Jing-wei

2016-07-01

Sensitivity to low rhizosphere soil aeration may change over time and therefore plant response may also depend on different growth stages of a crop. This study quantified effects of soil aeration during 5 different periods, on growth and yield of trickle-irrigated potted single tomato plants. Irrigation levels were 0.6 to 0.7 (low level) or 0.7 to 0.8 (high level) of total water holding capacity of the pots. Soil was aerated by injecting 2.5 l of air into each pot through the drip tubing immediately after irrigation. Fresh fruit yield, above ground plant dry weight, plant height, and leaf area index response to these treatments were measured. For all these 4 response variables, means of post-infiltration aeration between 58 to 85 days after sowing were 13.4, 43.5, 13.7, and 37.7% higher than those for the non-aerated pots, respectively. The results indicated that: post-infiltration soil aeration can positively impact the yield and growth of sub-surface trickle-irrigated potted tomato plants; positive effects on plant growth can be obtained with aeration during the whole growth period or with aeration for partial periods; positive growth effects of partial periods of aeration appears to persist and result in yield benefit.

Effect of influent aeration on removal of organic matter from coffee processing wastewater in constructed wetlands.

PubMed

Rossmann, Maike; Matos, Antonio Teixeira; Abreu, Edgar Carneiro; Silva, Fabyano Fonseca; Borges, Alisson Carraro

2013-10-15

The aim of the present study was to evaluate the influence of aeration and vegetation on the removal of organic matter in coffee processing wastewater (CPW) treated in 4 constructed wetlands (CWs), characterized as follows: (i) ryegrass (Lolium multiflorum) cultivated system operating with an aerated influent; (ii) non-cultivated system operating with an aerated influent, (iii) ryegrass cultivated system operating with a non-aerated influent; and (iv) non-cultivated system operating with a non-aerated influent. The lowest average chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal efficiencies of 87, 84 and 73%, respectively, were obtained in the ryegrass cultivated system operating with a non-aerated influent. However, ryegrass cultivation did not influence the removal efficiency of organic matter. Artificial aeration of the CPW, prior to its injection in the CW, did not improve the removal efficiencies of organic matter. On other hand it did contribute to increase the instantaneous rate at which the maximum COD removal efficiency was reached. Although aeration did not result in greater organic matter removal efficiencies, it is important to consider the benefits of aeration on the removal of the other compounds. Copyright © 2013 Elsevier Ltd. All rights reserved.

Remediation of Urban River Water by Pontederia Cordata Combined with Artificial Aeration: Organic Matter and Nutrients Removal and Root-Adhered Bacterial Communities.

PubMed

Gu, Dungang; Xu, Huan; He, Yan; Zhao, Feng; Huang, Minsheng

2015-01-01

Macrophyte combined with artificial aeration is a promising in situ remediation approach for urban rivers polluted with nutrients and organic matter. However, seasonal variations and aeration effects on phytoremediation performance and root-adhered microbial communities are still unclear. In this study, Pontederia cordata was used to treat polluted urban river water under various aeration intensities. Results showed that the highest removal efficiencies of chemical oxygen demand (COD(Cr)) and total nitrogen (TN) were attained under aeration of 30 L min(-1) in spring and summer and 15 L min(-1) in autumn, while total phosphorus (TP) removal reached maximum with aeration of 15 L min(-1) in all seasons. Moderate aeration was beneficial for increasing the diversity of root-adhered bacteria communities, and the shift of bacterial community structure was more pronounced in spring and autumn with varying aeration intensity. The dual effect, i.e. turbulence and dissolved oxygen (DO), of aeration on the removal of COD(Cr) and TN prevailed over the individual effect of DO, while DO was the most influential factor for TP removal and the root-adhered bacterial community diversity. P. cordata combined with 15 L min(-1) aeration was deemed to be the best condition tested in this study.

In situ nitrogen removal from leachate by bioreactor landfill with limited aeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao Liming; He Pinjing; Li Guojian

2008-07-01

The feasibility of simultaneous nitrification and denitrification in a bioreactor landfill with limited aeration was assessed. Three column reactors, simulating bioreactor landfill operations under anaerobic condition (as reference), intermittent forced aeration and enhanced natural aeration were hence established, where aerated columns passed through two phases, i.e., fresh landfill and well-decomposed landfill. The experimental results show that limited aeration decreased nitrogen loadings of leachate distinctly in the fresh landfill. In the well-decomposed landfill, the NH{sub 4}{sup +}-N of the input leachate could be nitrified completely in the aerated landfill columns. The nitrifying loadings of the column cross section reached 7.9 gmore » N/m{sup 2} d and 16.9 g N/m{sup 2} d in the simulated landfill columns of intermittent forced aeration and enhanced natural aeration, respectively. The denitrification was influenced by oxygen distribution in the landfill column. Intermittent existence of oxygen in the landfill with the intermittent forced aeration was favorable to denitrify the NO{sub 2}{sup -}-N and NO{sub 3}{sup -}-N, indicated by the high denitrification efficiency (>99%) under the condition of BOD{sub 5}/TN of more than 5.4 in leachate; locally persistent existence of oxygen in the landfill with enhanced natural aeration could limit the denitrification, indicated by relatively low denitrification efficiency of about 75% even when the BOD{sub 5}/TN in leachate had an average of 7.1.« less

Effects of aeration frequency on leachate quality and waste in simulated hybrid bioreactor landfills.

PubMed

Ko, Jae Hac; Ma, Zeyu; Jin, Xiao; Xu, Qiyong

2016-12-01

Research has been conducted to investigate the effects of daily aeration frequency on leachate quality and waste settlement in simulated hybrid landfill bioreactors. Four laboratory-scale reactors were constructed and operated for about 10 months to simulate different bioreactor operations, including one anaerobic bioreactor and three hybrid bioreactors with different aeration frequencies (one, two, and four times per day). Chemical oxygen demand (COD) and biochemical oxygen demand (BOD 5 ) reduced more than 96% of the initial concentrations in all aerated bioreactors. The differences of COD and BOD 5 reductions among tested aeration frequencies were relatively small. For ammonia nitrogen, the higher aeration frequency (two or four times per day) resulted in the quicker reduction. Overall, the concentrations of heavy metals (Cr, Co, Cu, Mn, Ni, and Zn) decreased over time except Cd and Pb. The reduction of redox-sensitive metal concentrations (Mn, Co, Ni, and Cu) was greater in aerated bioreactors than in anaerobic bioreactor. Settlement of municipal solid waste (MSW) was enhanced with higher frequency of aeration events (four times per day). In recent years, hybird bioreactor landfill technology has gained a lot of attention. Appropriate aeration rate is crucial for hybrid bioreactor operation, but few studies have been done and different results were obtained. Research was conducted to investigate the effects of daily aeration frequency on leachate quality and waste settlement. Results indicated that aeration can effectively accelerate waste stabilization and remove organic carbon concentration and total nitrogen in the leachate.

Influence of aeration implements, phosphorus fertilizers, and soil taxa on phosphorus losses from grasslands.

PubMed

Franklin, D H; Butler, D M; Cabrera, M L; Calvert, V H; West, L T; Rema, J A

2011-01-01

Attenuation of rainfall within the solum may help to move contaminants and nutrients into the soil to be better sequestered or utilized by crops. Surface application of phosphorus (P) amendments to grasslands may lead to elevated concentrations of P in surface runoff and eutrophication of surface waters. Aeration of grasslands has been proposed as a treatment to reduce losses of applied P. Here, results from two small-plot aeration studies and two field-scale, paired-watershed studies are supplemented with previously unpublished soil P data and synthesized. The overall objective of these studies was to determine the impact of aeration on soil P, runoff volume, and runoff P losses from mixed tall fescue [Lolium arundinaceum (Schreb.) Darbysh.]-bermudagrass (Cynodon dactylon L.) grasslands fertilized with P. Small-scale rainfall simulations were conducted on two soil taxa using three types of aeration implements: spikes, disks, and cores. The-field scale study was conducted on four soil taxa with slit and knife aeration. Small-plot studies showed that core aeration reduced loads of total P and dissolved reactive P (DRP) in runoff from plots fertilized with broiler litter and that aeration was effective in reducing P export when it increased soil P in the upper 5 cm. In the field-scale study, slit aeration reduced DRP losses by 35% in fields with well-drained soils but not in poorly drained soils. Flow-weighted concentrations of DRP in aerated fields were related to water-soluble P applied in amendments and soil test P in the upper 5 cm. These studies show that the overall effectiveness of mechanical soil aeration on runoff volume and P losses is controlled by the interaction of soil characteristics such as internal drainage and compaction, soil P, type of surface-applied manure, and type of aeration implement.

Catfish production using intensive aeration

USDA-ARS?s Scientific Manuscript database

For the last 3 years, researchers at UAPB and NWAC have been monitoring and verifying production yields in intensively aerated catfish ponds with aeration rates greater than 6 hp/acre. We now have three years of data on commercial catfish production in intensively aerated ponds. With stocking densi...

Effect of famine-phase reduced aeration on polyhydroxyalkanoate accumulation in aerobic granules.

PubMed

Vjayan, T; Vadivelu, V M

2017-12-01

The effects of variable aeration in the famine period on polyhydroxyalkanoate (PHA) accumulation in aerobic granules were investigated. Results showed that regardless of the aeration rates used during famine period, all aerobic granules achieved a similar chemical oxygen demand removal and PHA content. The decrease in famine-period aeration rates accelerated the maximum PHA accumulation together with increase in granular size and settling ability. The PHA-accumulating microorganisms were found to have shifted closer to the surface of the granules when the aeration rate was reduced. Moreover, PHA compositional changes occurred, where the hydroxyvalerate content had increased with the reduction in aeration rate. Ultimately, the results indicate that the requirement of aeration for PHA accumulation in aerobic granules is highly insignificant in the famine phase. PHA production in aerobic granules under zero aeration in the famine period may result in an energy input reduction of up to 74%. Copyright © 2017 Elsevier Ltd. All rights reserved.

Improving microalgal growth with reduced diameters of aeration bubbles and enhanced mass transfer of solution in an oscillating flow field.

PubMed

Yang, Zongbo; Cheng, Jun; Lin, Richen; Zhou, Junhu; Cen, Kefa

2016-07-01

A novel oscillating gas aerator combined with an oscillating baffle was proposed to generate smaller aeration bubbles and enhance solution mass transfer, which can improve microalgal growth in a raceway pond. A high-speed photography system (HSP) was used to measure bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure mass-transfer coefficient and mixing time. Bubble diameter and generation time decreased with decreased aeration gas rate, decreased orifice diameter, and increased water velocity in the oscillating gas aerator. The optimized oscillating gas aerator decreased bubble diameter and generation time by 25% and 58%, respectively, compared with a horizontal tubular gas aerator. Using an oscillating gas aerator and an oscillating baffle in a raceway pond increased the solution mass-transfer coefficient by 15% and decreased mixing time by 32%; consequently, microalgal biomass yield increased by 19%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of intermittent aerations on leachate quality and greenhouse gas reduction in the aerobic-anaerobic landfill method.

PubMed

Nag, Mitali; Shimaoka, Takayuki; Komiya, Teppei

2016-09-01

The aerobic-anaerobic landfill method (AALM) is a novel approach in solid waste management that could shorten the landfill post-closure period and minimize the environmental loads. In this study, the aerobic-anaerobic landfill method was evaluated by using intermittent aeration. In addition, the nitrification-denitrification process was assessed as a means of reducing the emission of greenhouse gases (GHGs) and improving the leachate quality during the degradation of the organic solid waste. The leachate quality and the gas composition in each of the reactors were measured during the experimental period (408days). The aeration process entailed the injection of air into plexiglass cylinders (200cm height×10 cm diameter), filled with fresh organic solid waste collected from a composting plant. Different aeration routines were applied, namely, continuous aeration (aerobic reactor A), aeration for three days/week (aerobic-anaerobic reactor B), aeration for 6h/day (aerobic-anaerobic reactor C), and no aeration (non-aerated reactor D). It was found that aerobic reactor A produced the best results in terms of reduction of GHGs and improvement of the leachate quality. The aerobic-anaerobic reactor C was found to be more effective than reactor B in respect of both the emission of GHGs and the leachate quality; moreover, compared with aerobic reactor A, energy costs were reduced by operating this reactor. The transition period phenomenon was investigated during an intensive seven-day experiment conducted on the discharged leachate obtained from aerobic-anaerobic reactors B and C. The experiment concerned the differences in the composition of the gas during the aeration and the non-aeration periods. It was found that the transition period between the aeration and non-aeration cycles, which followed the simultaneous nitrification-denitrification had a considerable effect on the leachate quality of both the reactors. The results indicated that AALM has the potential to reduce leachate pollutants and the emission of GHGs. Furthermore, the occurrence of simultaneous nitrification-denitrification presents the prospect that intermittent aeration could reduce landfill aftercare and energy costs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optimization of micro-aeration intensity in acidogenic reactor of a two-phase anaerobic digester treating food waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Suyun; Sino-Forest Applied Research Centre for Pearl River Delta Environment, Department of Biology, Hong Kong Baptist University, Hong Kong Special Administrative Region; Selvam, Ammaiyappan

Highlights: • Effect of micro-aeration on acidogenesis and hydrolysis of food waste was investigated. • Micro-aeration at 258 L-air/kg TS/d increased the VFAs production 3-fold. • High aeration leads to loss of substrate through microbial biomass and respiration. • Optimum aeration increased methane recovery while high aeration intensity reduced methane yield. - Abstract: Micro-aeration is known to promote the activities of hydrolytic exo-enzymes and used as a strategy to improve the hydrolysis of particulate substrate. The effect of different micro-aeration rates, 0, 129, 258, and 387 L-air/kg TS/d (denoted as LBR-AN, LBR-6h, LBR-3h and LBR-2h, respectively) on the solubilization ofmore » food waste was evaluated at 35 °C in four leach bed reactors (LBR) coupled with methanogenic upflow anaerobic sludge blanket (UASB) reactor. Results indicate that the intensity of micro-aeration influenced the hydrolysis and methane yield. Adequate micro-aeration intensity in LBR-3h and LBR-2h significantly enhanced the carbohydrate and protein hydrolysis by 21–27% and 38–64% respectively. Due to the accelerated acidogenesis, more than 3-fold of acetic acid and butyric acid were produced in LBR-3h as compared to the anaerobic treatment LBR-AN resulting in the maximum methane yield of 0.27 L CH{sub 4}/g VS{sub added} in the UASB. The performance of LBR-6h with inadequate aeration was similar to that of LBR-AN with a comparable hydrolysis degree. Nevertheless, higher aeration intensity in LBR-2h was also unfavorable for methane yield due to significant biomass generation and CO{sub 2} respiration of up to 18.5% and 32.8% of the total soluble hydrolysate, respectively. To conclude, appropriate micro-aeration rate can promote the hydrolysis of solid organic waste and methane yield without undesirable carbon loss and an aeration intensity of 258 L-air/kg TS/d is recommended for acidogenic LBR treating food waste.« less

Yields and Nutritional of Greenhouse Tomato in Response to Different Soil Aeration Volume at two depths of Subsurface drip irrigation

PubMed Central

Li, Yuan; Niu, Wenquan; Dyck, Miles; Wang, Jingwei; Zou, Xiaoyang

2016-01-01

This study investigated the effects of 4 aeration levels (varied by injection of air to the soil through subsurface irrigation lines) at two subsurface irrigation line depths (15 and 40 cm) on plant growth, yield and nutritional quality of greenhouse tomato. In all experiments, fruit number, width and length, yield, vitamin C, lycopene and sugar/acid ratio of tomato markedly increased in response to the aeration treatments. Vitamin C, lycopene, and sugar/acid ratio increased by 41%, 2%, and 43%, respectively, in the 1.5 times standard aeration volume compared with the no-aeration treatment. An interaction between aeration level and depth of irrigation line was also observed with yield, fruit number, fruit length, vitamin C and sugar/acid ratio of greenhouse tomato increasing at each aeration level when irrigation lines were placed at 40 cm depth. However, when the irrigation lines were 15 cm deep, the trend of total fruit yields, fruit width, fruit length and sugar/acid ratio first increased and then decreased with increasing aeration level. Total soluble solids and titrable acid decreased with increasing aeration level both at 15 and 40 cm irrigation line placement. When all of the quality factors, yields and economic benefit are considered together, the combination of 40 cm line depth and “standard” aeration level was the optimum combination. PMID:27995970

Directional Flow of Summer Aeration to Manage Insect Pests in Stored Wheat

USDA-ARS?s Scientific Manuscript database

Field trials were conducted in metal wheat storage bins to determine whether pressure aeration, pushing ambient air from the bottom, or suction aeration, pulling air down from the top, would be more efficient at cooling the wheat mass and thereby limiting insect population growth. Aeration was accom...

Temperature stratification and insect pest populations in stored wheat with suction versus pressure aeration

USDA-ARS?s Scientific Manuscript database

A three-year study was conducted to compare temperature profiles in the headspace and in the bulk mass of wheat aerated through pressure aeration and suction aeration. Insect pitfall traps were used to measure naturally-occurring populations of stored product insects. Results show uniform distributi...

The Study of Micro-Pressure Inner-Loop Bioreactor Oxygen Mass Transfer Characteristics

NASA Astrophysics Data System (ADS)

Wan, L. G.; Lin, Q.; Bian, D. J.; Ren, Q. K.; Xiao, Y. B.; Lu, W. X.

2018-03-01

The oxygen mass transfer characteristics in a Micro-Pressure Inner-Loop bioreactor (MPR) were studied by clean water oxygenation experiment, the results show that when the aeration adopt by 0.1, 0.2, 0.4, 0.6 m3·h-1, respectively, the oxygen mass transfer coefficient KLa(20) in the reactor increases with the increase of the aeration. KLa(20) shows a good linear correlation with the aeration. The rate is 0.2128 h·m-3·min-1 and the correlation coefficient R=0.993. However, the trend of EO2 increases first and then decreases with the increase of aeration. When the aeration increased to 0.4 m3·h-1, the EO2 reaches the maximum. If aeration increases constantly, EO2 begin to decrease excessive aeration may lead to an increase in energy waste during reactor operation.

Enhancing recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membrane technology.

PubMed

Dube, P J; Vanotti, M B; Szogi, A A; García-González, M C

2016-03-01

Gas-permeable membrane technology is useful to recover ammonia from manure. In this study, the technology was enhanced using aeration instead of alkali chemicals to increase pH and the ammonium (NH4(+)) recovery rate. Digested effluents from covered anaerobic swine lagoons containing 1465-2097 mg NH4(+)-N L(-1) were treated using submerged membranes (0.13 cm(2) cm(-3)), low-rate aeration (120 mL air L-manure(-1) min(-1)) and nitrification inhibitor (22 mg L(-1)) to prevent nitrification. The experiment included a control without aeration. The pH of the manure with aeration rose from 8.6 to 9.2 while the manure without aeration decreased from 8.6 to 8.1. With aeration, 97-99% of the NH4(+) was removed in about 5 days of operation with 96-98% recovery efficiency. In contrast, without aeration it took 25 days to treat the NH4(+). Therefore, the recovery of NH4(+) was five times faster with the low-rate aeration treatment. This enhancement could reduce costs by 70%. Published by Elsevier Ltd.

Study of the liquid-film-forming apparatus as an alternative aeration system: design criteria and operating condition.

PubMed

Hongprasith, Narapong; Imai, Tsuyoshi; Painmanakul, Pisut

2017-06-01

Aeration is an important factor in aquaculture systems because it is a vital condition for all organisms that live in water and respire aerobically. Generally, mechanical surface aerators are widely used in Thailand due to their advantage for increasing dissolved oxygen (DO) and for their horizontal mixing of aquaculture ponds with large surface areas. However, these systems still have some drawbacks, primarily the low oxygen transfer efficiency (OTE) and energy. Regarding this issue, alternative aeration systems should be studied and applied. Therefore, this research aims to study the aeration mechanism obtained by the diffused-air aeration combined with a liquid-film-forming apparatus (LFFA). The effect of gas flow rates, types, and patterns of aerator installation were investigated in an aquaculture pond of 10 m × 10 m × 1.5 m. The analytical parameters were volumetric mass transfer coefficient (k L a), OTE, and aeration efficiency (AE). From the results, the '4-D' with partitions was proposed as the suitable pattern for the LFFA installation. The advantage could be obtained from high energy performance with 1.2 kg/kW h of AE. Then, the operation conditions can be applied as a design guideline for this alternative aeration system in the aquaculture ponds.

Landfill aeration in the framework of a reclamation project in Northern Italy.

PubMed

Raga, Roberto; Cossu, Raffaello

2014-03-01

In situ aeration by means of the Airflow technology was proposed for landfill conditioning before landfill mining in the framework of a reclamation project in Northern Italy. A 1-year aeration project was carried out on part of the landfill with the objective of evaluating the effectiveness of the Airflow technology for landfill aerobization, the evolution of waste biological stability during aeration and the effects on leachate and biogas quality and emissions. The main outcomes of the 1-year aeration project are presented in the paper. The beneficial effect of the aeration on waste biological stability was clear (63% reduction of the respiration index); however, the effectiveness of aeration on the lower part of the landfill is questionable, due to the limited potential for air migration into the leachate saturated layers. During the 1-year in situ aeration project approx. 275 MgC were discharged from the landfill body with the extracted gas, corresponding to 4.6 gC/kgDM. However, due to the presence of anaerobic niches in the aerated landfill, approx. 46% of this amount was extracted as CH4, which is higher than reported in other aeration projects. The O2 conversion quota was lower than reported in other similar projects, mainly due to the higher air flow rates applied. The results obtained enabled valuable recommendations to be made for the subsequent application of the Airflow technology to the whole landfill. Copyright © 2013 Elsevier Ltd. All rights reserved.

Bioreactor tests preliminary to landfill in situ aeration: A case study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raga, Roberto, E-mail: roberto.raga@unipd.it; Cossu, Raffaello

Highlights: ► Carbon and nitrogen mass balances in aerated landfill simulation reactors. ► Waste stabilization in aerated landfill simulation reactors. ► Effect of temperature on biodegradation processes in aerated landfills. - Abstract: Lab scale tests in bioreactor were carried out in the framework of the characterization studies of a landfill where in situ aeration (possibly followed by landfill mining) had been proposed as part of the novel waste management strategy in a region in northern Italy. The tests were run to monitor the effects produced by aerobic conditions at different temperatures on waste sampled at different depths in the landfill,more » with focus on the carbon and nitrogen conversion during aeration. Temperatures ranging from 35 to 45 °C were chosen, in order to evaluate possible inhibition of biodegradation processes (namely nitrification) at 45 °C in the landfill. The results obtained showed positive effects of the aeration on leachate quality and a significant reduction of waste biodegradability. Although a delay of biodegradation processes was observed in the reactor run at 45 °C, biodegradation rates increased after 2 months of aeration, providing very low values of the relevant parameters (as in the other aerated reactors) by the end of the study. Mass balances were carried out for TOC and N-NH{sub 4}{sup +}; the findings obtained were encouraging and provided evidence of the effectiveness of carbon and nitrogen conversion processes in the aerated landfill simulation reactors.« less

Study on low intensity aeration oxygenation model and optimization for shallow water

NASA Astrophysics Data System (ADS)

Chen, Xiao; Ding, Zhibin; Ding, Jian; Wang, Yi

2018-02-01

Aeration/oxygenation is an effective measure to improve self-purification capacity in shallow water treatment while high energy consumption, high noise and expensive management refrain the development and the application of this process. Based on two-film theory, the theoretical model of the three-dimensional partial differential equation of aeration in shallow water is established. In order to simplify the equation, the basic assumptions of gas-liquid mass transfer in vertical direction and concentration diffusion in horizontal direction are proposed based on engineering practice and are tested by the simulation results of gas holdup which are obtained by simulating the gas-liquid two-phase flow in aeration tank under low-intensity condition. Based on the basic assumptions and the theory of shallow permeability, the model of three-dimensional partial differential equations is simplified and the calculation model of low-intensity aeration oxygenation is obtained. The model is verified through comparing the aeration experiment. Conclusions as follows: (1)The calculation model of gas-liquid mass transfer in vertical direction and concentration diffusion in horizontal direction can reflect the process of aeration well; (2) Under low-intensity conditions, the long-term aeration and oxygenation is theoretically feasible to enhance the self-purification capacity of water bodies; (3) In the case of the same total aeration intensity, the effect of multipoint distributed aeration on the diffusion of oxygen concentration in the horizontal direction is obvious; (4) In the shallow water treatment, reducing the volume of aeration equipment with the methods of miniaturization, array, low-intensity, mobilization to overcome the high energy consumption, large size, noise and other problems can provide a good reference.

The in situ aeration in an old landfill in China: Multi-wells optimization method and application.

PubMed

Liu, Lei; Ma, Jun; Xue, Qiang; Shao, Jingbang; Chen, Yijun; Zeng, Gang

2018-06-01

The optimization design of well spacing (WS) and aeration rate (AR) is crucial to the in situ aeration system operation in under long-term and high-efficiency conditions. This optimization design aims to transport additional air into landfills and to develop an improved oxygen environment for enhancing aerobic degradation. Given the specific pore structure distribution within landfills, providing sufficient oxygen in all waste bodies in field sites through gas wells is difficult. The design of well distribution also lacks adequate criteria. In this work, the multi-well optimization aeration method (MWOAM) was proposed to select the WS and AR from prediction results that consider gas transport properties by maximizing oxygen storage ratio (OSR) as the key objective threshold. This method was applied to the aeration restoration engineering in Jinkou landfill, which represents the first full-scale application of an aeration project in China, to optimize the operation scheme of the aeration system. Results of the gas concentration monitoring show that the trend of the OSR with aeration time based on the measurement agrees with the prediction. The oxygen and methane contents remain high and low within the landfill during the aeration process, respectively. Moreover, the temperature in the waste body did not exceed the upper limit value. These results suggested that the MWOAM is an effective means of supplying sufficient oxygen content across the landfill body and extend the aeration system operation for the long term. Therefore, this work provides reliable evidence to support the design and operation management of the aeration systems in full-scale landfills. Copyright © 2018 Elsevier Ltd. All rights reserved.

A novel circulating loop bioreactor with cells immobilized in loofa ( Luffa cylindrica) sponge for the bioconversion of raw cassava starch to ethanol.

PubMed

Roble, N D; Ogbonna, J C; Tanaka, H

2003-02-01

A circulating loop bioreactor (CLB) with cells immobilized in loofa sponge was constructed for simultaneous aerobic and anaerobic processes. The CLB consists of an aerated riser and a non-aerated downcomer column connected at the top and bottom by cylindrical pipes. Ethanol production from raw cassava starch was investigated in the CLB. Aspergillus awamori IAM 2389 and Saccharomyces cerevisiae IR2 immobilized on loofa sponge were placed, respectively, in the aerated riser column and non-aerated downcomer column. Both alpha-amylase and glucoamylase activities increased as the aeration rate was increased. Ethanol yield and productivity increased with an increase in the aeration rate up to 0.5 vvm, but decreased at higher aeration rates. The CLB was operated at an aeration rate of 0.5 vvm for more than 600 h, resulting in an average ethanol productivity and yield from raw cassava starch of 0.5 g-ethanol l(-1) x h(-1) and 0.45 g ethanol/g starch, respectively. In order to increase ethanol productivity, it was necessary to increase the dissolved oxygen (DO) concentration in the riser column and decrease the DO concentration in the downcomer column. However, increasing the aeration rate resulted in increases in the DO concentration in both the riser and the downcomer columns. At high aeration rate, there was no significant difference in the DO concentration in the riser and downcomer columns. The aeration rate was therefore uncoupled from the liquid circulation by attaching a time-controlled valve in the upper connecting pipe. By optimizing the time and frequency of valve opening, and operation at high aeration rate, it was possible to maintain a very high DO concentration in the riser column and a low DO concentration in the downcomer column. Under these conditions, ethanol productivity increased by more than 100%, to 1.17 g l(-1) x h(-1).

High aeration rate enhances flow stratification in full-scale oxidation ditch.

PubMed

Diamantis, Vasileios; Papaspyrou, Ioannis; Melidis, Parasxos; Aivasidis, Alexander

2010-02-01

Aerated channel reactors with a uniform field of aeration may display flow stratification and short-circuit phenomena in wastewater treatment systems. In this study, we present data suggesting that flow stratification is closely related to the aeration rate and the arrangement of aerators. A full-scale oxidation ditch, with a total volume of 6,500 m(3) and a membrane-diffused aerated zone of 60 x 7 x 5 m (length-width-depth), was selected for water velocity measurements. Two profiles of the oxidation ditch were studied in detail: the first one was at the end of the aerated zone and the second one at the end of the anoxic zone. The results of this work demonstrate that the horizontal water velocity at the end of the aerated zone displayed significant stratification, with maximum velocity near the water surface (0.5-0.7 m/s) and almost zero velocity at a depth of 2.5 m. At the end of the anoxic zone, water velocity was uniform and equal to 0.27-0.31 m/s. Increasing the aeration rate from 1,800 to 4,300 m(3)/h, almost 90% of the water flow was found to discharge through the upper-half of the channel reactor profile. Different options to mitigate flow stratification of the oxidation ditch are discussed in this paper.

Effect of process design and operating parameters on aerobic methane oxidation in municipal WWTPs.

PubMed

Daelman, Matthijs R J; Van Eynde, Tamara; van Loosdrecht, Mark C M; Volcke, Eveline I P

2014-12-01

Methane is a potent greenhouse gas and its emission from municipal wastewater treatment plants (WWTPs) should be prevented. One way to do this is to promote the biological conversion of dissolved methane over stripping in aeration tanks. In this study, the well-established Activated Sludge Model n°1 (ASM1) and Benchmark Simulation Model n°1 (BSM1) were extended to study the influence of process design and operating parameters on biological methane oxidation. The aeration function used in BSM 1 was upgraded to more accurately describe gas-liquid transfer of oxygen and methane in aeration tanks equipped with subsurface aeration. Dissolved methane could be effectively removed in an aeration tank at an aeration rate that is in agreement with optimal effluent quality. Subsurface bubble aeration proved to be better than surface aeration, while a CSTR configuration was superior to plug flow conditions in avoiding methane emissions. The conversion of methane in the activated sludge tank benefits from higher methane concentrations in the WWTP's influent. Finally, if an activated sludge tank is aerated with methane containing off-gas, a limited amount of methane is absorbed and converted in the mixed liquor. This knowledge helps to stimulate the methane oxidizing capacity of activated sludge in order to abate methane emissions from wastewater treatment to the atmosphere. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dissolved Oxygen management in catfish ponds using electric paddlewheel aerators: new approaches with old technology

USDA-ARS?s Scientific Manuscript database

The electric paddlewheel aerator has been the main aerator used in the U.S. catfish industry for the post forty years. While it has its limitations, it is perhaps the most efficient shallow-water aerator yet to be developed. Its shortcomings result not so much from poor design, as from poor usage. U...

Application of micro bubble generator as low cost and high efficient aerator for sustainable fresh water fish farming

NASA Astrophysics Data System (ADS)

Budhijanto, Wiratni; Darlianto, Deen; Pradana, Yano Surya; Hartono, Muhamad

2017-05-01

This study aimed to apply a novel type of aerator called Micro Bubble Generator (MBG) for fresh water fish farming. The MBG was run based on the principle of venturi tube in which water was circulated through a narrowed channel so that air was sucked into the device and pushed by the flowing water to create micro-sized bubble. The MBG aerator was tested on the aquaculture of tilapia fish to be compared to conventional aerator (the bubbler currently used in aquaculture experiments) and control (container with no aeration). The population of 150 tilapia fish of the average initial length of 6.44 cm was tested in each container. The water quality parameters (COD, pH, and TAN) and fish growth parameters (length and weight) were observed for 68 days. The results highlighted the promising potential of MBG as affordable aerator to be applied in intensive aquaculture. Although the dissolved oxygen level did not differ significantly with the conventional aerator, MBG aerator indicated faster degradation of organic content in the water and induced faster growth of the fish as measured by their length and weight.

Influence of aeration during propagation of pitching yeast on fermentation and beer flavor.

PubMed

Cheong, Chul; Wackerbauer, Karl; Kang, Soon Ah

2007-02-01

The effect of yeast propagated at different aeration conditions on yeast physiology, fermentation ability, and beer quality was investigated using three strains of Saccharomyces cerevisiae. It was shown that yeast cells grown under continuous aeration conditions during propagation were almost two times higher as compared with discontinuous aeration conditions. The maximum of cell growth of all samples reached between 36 h and 48 h. The concentration of trehalose was increased under continuous aerated yeasts, whereas glycogen was decreased. It was also observed that the concentration of glycogen and trehalose in yeast cells had no direct effect on subsequent fermentation ability. The effect of yeast propagated under different aeration conditions on subsequent fermentation ability was different from yeast strains, in which the influence will be most pronounced at the first fermentation. Later, the yeasts might regain its original characteristics in the following fermentations. Generally, continuously propagated yeast had a positive effect on beer quality in subsequent fermentation. Hence, the concentration of aroma compounds obtained with yeast propagated under 6 1/h for 48 h aeration was lower than those grown under other aeration conditions in the bottom yeasts; in particular, the amounts of phenylethyl alcohol, ester, and fatty acids were decreased.

Ammonia-based feedforward and feedback aeration control in activated sludge processes.

PubMed

Rieger, Leiv; Jones, Richard M; Dold, Peter L; Bott, Charles B

2014-01-01

Aeration control at wastewater treatment plants based on ammonia as the controlled variable is applied for one of two reasons: (1) to reduce aeration costs, or (2) to reduce peaks in effluent ammonia. Aeration limitation has proven to result in significant energy savings, may reduce external carbon addition, and can improve denitrification and biological phosphorus (bio-P) performance. Ammonia control for limiting aeration has been based mainly on feedback control to constrain complete nitrification by maintaining approximately one to two milligrams of nitrogen per liter of ammonia in the effluent. Increased attention has been given to feedforward ammonia control, where aeration control is based on monitoring influent ammonia load. Typically, the intent is to anticipate the impact of sudden load changes, and thereby reduce effluent ammonia peaks. This paper evaluates the fundamentals of ammonia control with a primary focus on feedforward control concepts. A case study discussion is presented that reviews different ammonia-based control approaches. In most instances, feedback control meets the objectives for both aeration limitation and containment of effluent ammonia peaks. Feedforward control, applied specifically for switching aeration on or off in swing zones, can be beneficial when the plant encounters particularly unusual influent disturbances.

Iodine-infused aeration for hull fouling prevention: a vessel-scale study.

PubMed

Dickenson, Natasha C; Krumholz, Jason S; Hunsucker, Kelli Z; Radicone, Michael

2017-11-01

Biofouling is a significant economic and ecological problem, causing reduced vessel performance and increases in fuel consumption and emissions. Previous research has shown iodine vapor (I 2 )-infused aeration to be an environmentally friendly method for deterring the settlement of fouling organisms. An aeration system was deployed on a vessel with hull sections coated with two types of antifoulant coatings, Intersleek ® 1100 (fouling-release) and Interspeed ® BRA-640 (ablative copper biocide), as well as an inert epoxy barrier coating, to assess the effectiveness of aeration in conjunction with common marine coatings. I 2 -infused aeration resulted in consistent reductions of 80-90% in hard fouling across all three coatings. Additionally, aeration reduced the soft fouling rate by 45-70% when used in conjunction with both Intersleek ® and Interspeed ® BRA versus those coatings alone. The results of this study highlight the contribution of I 2 -infused aeration as a standalone mechanism for fouling prevention or as a complement to traditional antifouling coatings.

Method and apparatus for energy efficient self-aeration in chemical, biochemical, and wastewater treatment processes

DOEpatents

Gao, Johnway [Richland, WA; Skeen, Rodney S [Pendleton, OR

2002-05-28

The present invention is a pulse spilling self-aerator (PSSA) that has the potential to greatly lower the installation, operation, and maintenance cost associated with aerating and mixing aqueous solutions. Currently, large quantities of low-pressure air are required in aeration systems to support many biochemical production processes and wastewater treatment plants. Oxygen is traditionally supplied and mixed by a compressor or blower and a mechanical agitator. These systems have high-energy requirements and high installation and maintenance costs. The PSSA provides a mixing and aeration capability that can increase operational efficiency and reduce overall cost.

[Optimization and comparison of nitrogen and phosphorus removal by different aeration modes in oxidation ditch].

PubMed

Guo, Chang-Zi; Peng, Dang-Cong; Cheng, Xue-Mei; Wang, Dan

2012-03-01

The oxidation ditch operation mode was simulated by sequencing batch reactor (SBR) system with alternate stirring and aeration. The nitrogen and phosphorus removal efficiencies were investigated in two different aeration modes: point aeration and step aeration. Experimental results show that oxygen is dissolved more efficiently in point aeration mode with a longer aerobic region in the same air supply capacity, but dissolved oxygen (DO) utilization efficiency for nitrogen and phosphorus removal is high in step aeration mode. Nitrification abilities of the two modes are equal with ammonia-nitrogen (NH4(+) -N) removal efficiency of 96.68% and 97.03%, respectively. Nitrifier activities are 4.65 and 4.66 mg x (g x h)(-1) respectively. When the ratio of anoxic zones and the aerobic zones were 1, the total nitrogen (TN) removal efficiency of point aeration mode in 2, 4 or 7 partitions was respectively 60.14%, 47.93% and 33.7%. The total phosphorus (TP) removal efficiency was respectively 28.96%, 23.75% and 24.31%. The less the partitions, the higher the nitrogen and phosphorus removal efficiencies, but it is in more favor of TN removal. As for step aeration mode with only one partitioning zone, the TN and TP removal efficiencies are respectively 64.21% and 49.09%, which is better than in point aeration mode, but more conducive to the improvement of TP removal efficiency. Under the condition of sufficient nitrification in step aeration mode, the nitrogen and phosphorus removal is better with the increase of anoxic zone. The removal efficiencies of TN and TP respectively rose to 73.94% and 54.18% when the ratio of anoxic zones and the aerobic zones was increased from 1 : 1 to 1. 8 : 1. As the proportion of anoxic zones was enlarged further, nitrification and operation stability were weakened so as to affect the nitrogen and phosphorus removal efficiencies.

Low frequency aeration of pig slurry affects slurry characteristics and emissions of greenhouse gases and ammonia.

PubMed

Calvet, Salvador; Hunt, John; Misselbrook, Tom H

2017-07-01

Low frequency aeration of slurries may reduce ammonia (NH 3 ) and methane (CH 4 ) emissions without increasing nitrous oxide (N 2 O) emissions. The aim of this study was to quantify this potential reduction and to establish the underlying mechanisms. A batch experiment was designed with 6 tanks with 1 m 3 of pig slurry each. After an initial phase of 7 days when none of the tanks were aerated, a second phase of 4 weeks subjected three of the tanks to aeration (2 min every 6 h, airflow 10 m 3  h -1 ), whereas the other three tanks remained as a control. A final phase of 9 days was established with no aeration in any tank. Emissions of NH 3 , CH 4 , carbon dioxide (CO 2 ) and N 2 O were measured. In the initial phase no differences in emissions were detected, but during the second phase aeration increased NH 3 emissions by 20% with respect to the controls (8.48 vs. 7.07 g m -3  [slurry] d -1 , P < 0.05). A higher pH was found in the aerated tanks at the end of this phase (7.7 vs. 7.0 in the aerated and control tanks, respectively, P < 0.05). CH 4 emissions were 40% lower in the aerated tanks (2.04 vs. 3.39 g m -3  [slurry] d -1 , P < 0.05). These differences in NH 3 and CH 4 emissions remained after the aeration phase had finished. No effect was detected for CO 2 , and no relevant N 2 O emissions were detected during the experiment. Our results demonstrate that low frequency aeration of stored pig slurry increases slurry pH and increases NH 3 emissions.

3D-modelling of the thermal circumstances of a lake under artificial aeration

NASA Astrophysics Data System (ADS)

Tian, Xiaoqing; Pan, Huachen; Köngäs, Petrina; Horppila, Jukka

2017-12-01

A 3D-model was developed to study the effects of hypolimnetic aeration on the temperature profile of a thermally stratified Lake Vesijärvi (southern Finland). Aeration was conducted by pumping epilimnetic water through the thermocline to the hypolimnion without breaking the thermal stratification. The model used time transient equation based on Navier-Stokes equation. The model was fitted to the vertical temperature distribution and environmental parameters (wind, air temperature, and solar radiation) before the onset of aeration, and the model was used to predict the vertical temperature distribution 3 and 15 days after the onset of aeration (1 August and 22 August). The difference between the modelled and observed temperature was on average 0.6 °C. The average percentage model error was 4.0% on 1 August and 3.7% on 22 August. In the epilimnion, model accuracy depended on the difference between the observed temperature and boundary conditions. In the hypolimnion, the model residual decreased with increasing depth. On 1 August, the model predicted a homogenous temperature profile in the hypolimnion, while the observed temperature decreased moderately from the thermocline to the bottom. This was because the effect of sediment was not included in the model. On 22 August, the modelled and observed temperatures near the bottom were identical demonstrating that the heat transfer by the aerator masked the effect of sediment and that exclusion of sediment heat from the model does not cause considerable error unless very short-term effects of aeration are studied. In all, the model successfully described the effects of the aerator on the lake's temperature profile. The results confirmed the validity of the applied computational fluid dynamic in artificial aeration; based on the simulated results, the effect of aeration can be predicted.

Performance and completion assessment of an in-situ aerated municipal solid waste landfill - Final scientific documentation of an Austrian case study.

PubMed

Hrad, Marlies; Huber-Humer, Marion

2017-05-01

By converting anaerobic landfills into a biologically stabilized state through accelerating aerobic organic matter degradation, the effort and duration necessary for post-closure procedures can be shortened. In Austria, the first full-scale application of in-situ landfill aeration by means of low pressure air injection with simultaneous off-gas collection and treatment was implemented on an old MSW-landfill and operated between 2007 and 2013. Besides complementary laboratory investigations, which included waste sampling from the landfill site prior to aeration start, a comprehensive field monitoring program was conducted to assess the influence of the aeration measure on the emission behavior of the landfilled waste during the aeration period as well as after aeration completion. Although the initial waste material was described as rather stable, the lab-scale aeration tests indicated a significant improvement of the leachate quality and even the biological solid waste stability. However, the aeration success was less pronounced for the application at the landfill site, mainly due to technical limitations in the full-scale operation. In this paper main performance data of the field investigation are compared to four other scientifically documented case studies along with stability indicators for solid waste and leachate characteristics in order to evaluate the success of aeration as well as the progress of a landfill towards completion and end of post-closure care. A number of quantitative benchmarks and relevant context information for the performance assessment of the five hitherto conducted international aeration projects are proposed aiming to support the systematization and harmonization of available results from diverse field studies and full-scale applications in future. Copyright © 2016 Elsevier Ltd. All rights reserved.

Design of high efficiency and energy saving aeration device for aquaculture

NASA Astrophysics Data System (ADS)

Liu, Sibo

2017-03-01

Energy efficient aeration device for aquaculture, in line with "by more than a generation, dynamic aeration" train of thought for technical design and improvement. Removable aeration terminal as the core, multi-level water to improve the method, the mobile fading pore aeration, intelligent mobile and open and close as the main function, aimed at solving the existing pond aeration efficiency, low energy consumption is high, the function of a single problem. From energy saving, efficiency, biological bacteria on the three directions, the aquaculture industry of energy conservation and emissions reduction. Device of the main advantages are: 1, original mobile fading aerator on the one hand, to expand the scope of work, playing a micro porous aeration of dissolved oxygen with high efficiency and to achieve "by more than a generation", on the other hand, through the sports equipment, stir the mixture of water, the water surface of photosynthesis of plants rich in dissolved oxygen input parts of the tank, compared to the stillness of the aerator can be more fully dissolved oxygen.2, through the opening of the pressure sensor indirect control device, can make the equipment timely and stop operation, convenient in use at the same time avoid the waste of energy.3, the biofilm suspension in aeration terminal, can be accomplished by nitration of microbial multi-level water improvement, still can make biofilm increase rate of netting in the movement process, the biological and mechanical aerobic promote each other, improve the efficiency of both. In addition, the device has small power consumption, low cost of characteristics. And have a certain degree of technical barriers, have their own intellectual property rights, and high degree of product market demand, easily accepted by customers, has a very high popularization value.

The substitution of sand filtration by immersed-UF for surface water treatment: pilot-scale studies.

PubMed

Lihua, Sun; Xing, Li; Guoyu, Zhang; Jie, Chen; Zhe, Xu; Guibai, Li

2009-01-01

The newly issued National Drinking Water Standard required that turbidity should be lower than 1 NTU, and the substitution of sand filtration by immersed ultrafiltration (immersed-UF) is feasible to achieve the standard. This study aimed to optimise the operational processes (i.e. aeration, backwashing) through pilot scale studies, to control membrane fouling while treating the sedimentation effluent. Results indicated that the immersed-UF was promising to treat the sedimentation effluent. The turbidity was below 0.10 NTU, bacteria and E. coli were not detected in the permeate water. The intermittent filtration with aeration is beneficial to inhibit membrane fouling. The critical aeration intensity is observed to be 60.0 m(3) m(-2) h(-1). At this aeration intensity, the decline rate of permeate flux in one period of backwashing was 1.94% and 7.03% for intermittent filtration and sustained filtration respectively. The different membrane backwashing methods (i.e. aeration 1.5 min, synchronous aeration and water backwashing 2 min, water backwashing 1.5 min; synchronous aeration and water backwashing 3 min, water backwashing 2 min; aeration 3 min, single water backwashing 2 min; synchronous aeration and water backwashing 5 min; single water backwashing 5 min) on the recovery of permeate flux were compared, indicating that the synchronous aeration and water backwashing exhibited best potential for permeate flux recovery. The optimal intensity of water backwashing is shown to be 90.0 L m(-2) h(-1). When the actual water intensity was below or exceeded the value, the recovery rate of permeate flux would be reduced. Additionally, the average operating cost for the immersed UF membrane, including the power, the chemical cleaning reagents, and membrane modules replacement, was about 0.31 RMB/m(3).

Organics removal, nitrogen removal and N2O emission in subsurface wastewater infiltration systems amended with/without biochar and sludge.

PubMed

Sun, Yafei; Qi, Shiyue; Zheng, Fanping; Huang, Linli; Pan, Jing; Jiang, Yingying; Hou, Wanyuan; Xiao, Lu

2018-02-01

Organics removal, nitrogen removal, N 2 O emission and nitrogen removal functional gene abundances in four subsurface wastewater infiltration systems (SWISs), named SWIS A (no intermittent aeration without biochar and sludge), SWIS B (no intermittent aeration with biochar and sludge), SWIS C (intermittent aeration without biochar and sludge), SWIS D (intermittent aeration with biochar and sludge) were investigated. Intermittent aeration enhanced chemical oxygen demand (COD), ammonia nitrogen (NH 4 + -N), total nitrogen (TN) removal and the abundances of nitrogen removal functional genes (amoA, nxrA, napA, narG, nirS, nirK, qnorB and nosZ) compared to non-aerated SWISs. High COD (95.4 ± 0.2%), NH 4 + -N (96.2 ± 0.6%), TN (86.4 ± 0.5%) removal efficiencies and low N 2 O emission rate (18.4 mg/(m 2  d)) were obtained simultaneously in intermittent aerated SWIS amended with biochar and sludge. The results suggested that intermittent aerated SWISs amended with biochar and sludge could be an effective and appropriate method for improving treatment performance and reducing N 2 O emission. Copyright © 2017 Elsevier Ltd. All rights reserved.

Energy, cost and design aspects of coarse- and fine-bubble aeration systems in the MBBR IFAS process.

PubMed

Sander, S; Behnisch, J; Wagner, M

2017-02-01

With the MBBR IFAS (moving bed biofilm reactor integrated fixed-film activated sludge) process, the biomass required for biological wastewater treatment is either suspended or fixed on free-moving plastic carriers in the reactor. Coarse- or fine-bubble aeration systems are used in the MBBR IFAS process. In this study, the oxygen transfer efficiency (OTE) of a coarse-bubble aeration system was improved significantly by the addition of the investigated carriers, even in-process (∼1% per vol-% of added carrier material). In a fine-bubble aeration system, the carriers had little or no effect on OTE. The effect of carriers on OTE strongly depends on the properties of the aeration system, the volumetric filling rate of the carriers, the properties of the carrier media, and the reactor geometry. This study shows that the effect of carriers on OTE is less pronounced in-process compared to clean water conditions. When designing new carriers in order to improve their effect on OTE further, suppliers should take this into account. Although the energy efficiency and cost effectiveness of coarse-bubble aeration systems can be improved significantly by the addition of carriers, fine-bubble aeration systems remain the more efficient and cost-effective alternative for aeration when applying the investigated MBBR IFAS process.

Volume requirements for aerated mud drilling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, B.; Rajtar, J.M.

1995-09-01

Aerated mud drilling has been recognized as having many advantages over conventional mud drilling, such ass higher penetration rate, less formation damage, minimized lost circulation, and lower drilling cost. In some areas, the use of aerated mud as a circulating medium for drilling oil and gas wells is becoming an attractive practice. Maintaining an optimum combination of liquid and air flow rates is important in aerated drilling operations. However, most drilling operators are unclear on what constitutes the ``optimum combination of the liquid and air flow rates.`` Guo et al. presented a mathematical approach to determining the flowing bottomhole pressuremore » (BHP) for aerated mud drilling. This paper addresses the use of Guo et al.`s mathematical model to determine liquid and air volume requirements considering wellbore stability, pipe sticking, and formation damage as well as the cuttings-carry capacity of the aerated mud. For a formation-damage-prevention point of view, the liquid fraction in the fluid stream should e as low as possible. However, a sufficient mud flow rate is always required to make the hole stable and to maintain the cuttings-carrying capacity of the aerated mud without injecting much air volume. This paper provides a simple approach to determining the liquid and air volume requirements for aerated mud drilling.« less

Influence of aeration on CH4, N2O and NH3 emissions during aerobic composting of a chicken manure and high C/N waste mixture.

PubMed

Shen, Yujun; Ren, Limei; Li, Guoxue; Chen, Tongbin; Guo, Rui

2011-01-01

Co-composting of chicken manure, straw and dry grasses was investigated in a forced aeration system to estimate the effect of aeration rates on NH(3), CH(4) and N(2)O emissions and compost quality. Continuous measurements of gas emissions were carried out and detailed gas emission patterns were obtained using an intermittent-aeration of 30 min on/30 min off at rates of 0.01 (A1), 0.1 (A2) and 0.2 (A3) m(3)min(-1)m(-3). Concentrations of CH(4) and N(2)O at the low aeration rate (A1) were significantly greater than those at the other two rates, but there was no significant difference between the A2 and A3 treatments. CH(4) and N(2)O emissions for this mixture could be controlled when the composting process was aerobic and ammonia emissions were reduced at a lower aeration rate. Comparison of CH(4), N(2)O, NH(3) emissions and compost quality showed that the aeration rate of the A2 treatment was superior to the other two aeration rates. Copyright © 2010 Elsevier Ltd. All rights reserved.

Optimization of aeration for biodiesel production by Scenedesmus obliquus grown in municipal wastewater.

PubMed

Han, Song-Fang; Jin, Wenbiao; Tu, Renjie; Abomohra, Abd El-Fatah; Wang, Zhi-Han

2016-07-01

Despite the significant breakthroughs in research on microalgae as a feedstock for biodiesel, its production cost is still much higher than that of fossil diesel. One possible solution to overcome this problem is to optimize algal growth and lipid production in wastewater. The present study examines the optimization of pretreatment of municipal wastewater and aeration conditions in order to enhance the lipid productivity of Scenedesmus obliquus. Results showed that no significant differences were recorded in lipid productivity of S. obliquus grown in primary settled or sterilized municipal wastewater; however, ultrasound pretreatment of wastewater significantly decreased the lipid production. Whereas, aeration rates of 0.2 vvm significantly increased lipid content by 51 %, with respect to the non-aerated culture, which resulted in maximum lipid productivity (32.5 mg L(-1) day(-1)). Furthermore, aeration enrichment by 2 % CO2 resulted in increase of lipid productivity by 46 % over the CO2 non-enriched aerated culture. Fatty acid profile showed that optimized aeration significantly enhanced monounsaturated fatty acid production, composed mainly of C18:1, by 1.8 times over the non-aerated S. obliquus culture with insignificant changes in polyunsaturated fatty acid proportion; suggesting better biodiesel characteristics for the optimized culture.

The effect of aeration and effluent recycling on domestic wastewater treatment in a pilot-plant system of duckweed ponds.

PubMed

Ben-shalom, Miriam; Shandalov, Semion; Brenner, Asher; Oron, Gideon

2014-01-01

Three pilot-scale duckweed pond (DP) wastewater treatment systems were designed and operated to examine the effect of aeration and effluent recycling on treatment efficiency. Each system consisted of two DPs in series fed by pre-settled domestic sewage. The first system (duckweed+ conventional treatment) was 'natural' and included only duckweed plants. The second system (duckweed aeration) included aeration in the second pond. The third system (duckweed+ aeration+ circulation) included aeration in the second pond and effluent recycling from the second to the first pond. All three systems demonstrated similarly efficient removal of organic matter and nutrients. Supplemental aeration had no effect on either dissolved oxygen levels or on pollutant removal efficiencies. Although recycling had almost no influence on nutrient removal efficiencies, it had a positive impact on chemical oxygen demand and total suspended solids removals due to equalization of load and pH, which suppressed algae growth. Recycling also improved the appearance and growth rate of the duckweed plants, especially during heavy wastewater loads.

Effects of intermittent aeration periods on a structured-bed reactor continuously fed on the post-treatment of sewage anaerobic effluent.

PubMed

Silva, Bruno Garcia; Damianovic, Márcia Helena Rissato Zamariolli; Foresti, Eugenio

2018-04-20

This study assessed the simultaneous nitrification and denitrification processes and remaining organic matter removal from anaerobic reactor effluent treating wastewater in a single reactor. A structured-bed reactor, with polyurethane foam as support media, was subjected to intermittent aeration and effluent recirculation. Aerated/non-aerated periods varied in the range of 2/1-1/3 h. The chemical oxygen demand (COD) in the effluent remained between 26 and 42 mg L -1 throughout all the aeration conditions. Aeration periods of 1/2 h removed 80 and 26% of Total Kjeldahl Nitrogen and Total Nitrogen, respectively. A low solid production was observed during the 300 days of operation, resulting in a solid retention time of 139 days. The results indicate that the non-aerated periods generated alkalinity that favored nitrification, maintaining low COD concentrations in the effluent. The structured bed reactor presented a low solid production and effluent loss below 20 mgSSV L -1 , similar to concentrations obtained in secondary decanters.

Influence of aeration on volatile sulfur compounds (VSCs) and NH3 emissions during aerobic composting of kitchen waste.

PubMed

Zhang, Hongyu; Li, Guoxue; Gu, Jun; Wang, Guiqin; Li, Yangyang; Zhang, Difang

2016-12-01

This study investigates the influence of aeration on volatile sulfur compounds (VSCs) and ammonia (NH 3 ) emissions during kitchen waste composting. Aerobic composting of kitchen waste and cornstalks was conducted at a ratio of 85:15 (wet weight basis) in 60L reactors for 30days. The gas emissions were analyzed with force aeration at rates of 0.1 (A1), 0.2 (A2) and 0.3 (A3) L (kgDMmin) -1 , respectively. Results showed that VSCs emission at the low aeration rate (A1) was more significant than that at other two rates (i.e., A2 and A3 treatment), where no considerable emission difference was observed. On the other hand, NH 3 emission reduced as the aeration rate decreased. It is noteworthy that the aeration rate did not significantly affect the compost quality. These results suggest that the aeration rate of 0.2L (kgDMmin) -1 may be applied to control VSCs and NH 3 emissions during kitchen waste composting. Copyright © 2016 Elsevier Ltd. All rights reserved.

Grey-box modelling of aeration tank settling.

PubMed

Bechman, Henrik; Nielsen, Marinus K; Poulsen, Niels Kjølstad; Madsen, Henrik

2002-04-01

A model of the concentrations of suspended solids (SS) in the aeration tanks and in the effluent from these during Aeration tank settling (ATS) operation is established. The model is based on simple SS mass balances, a model of the sludge settling and a simple model of how the SS concentration in the effluent from the aeration tanks depends on the actual concentrations in the tanks and the sludge blanket depth. The model is formulated in continuous time by means of stochastic differential equations with discrete-time observations. The parameters of the model are estimated using a maximum likelihood method from data from an alternating BioDenipho waste water treatment plant (WWTP). The model is an important tool for analyzing ATS operation and for selecting the appropriate control actions during ATS, as the model can be used to predict the SS amounts in the aeration tanks as well as in the effluent from the aeration tanks.

Comparison between lab- and full-scale applications of in situ aeration of an old landfill and assessment of long-term emission development after completion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hrad, Marlies; Gamperling, Oliver; Huber-Humer, Marion, E-mail: marion.huber-humer@boku.ac.at

Highlights: ► Current data on in situ aeration effects from the first Austrian full-scale case study. ► Data on lasting waste stabilisation after aeration completion. ► Information on the transferability of results from lab- to full-scale aeration. - Abstract: Sustainable landfilling has become a fundamental objective in many modern waste management concepts. In this context, the in situ aeration of landfills has been recognised for its potential to convert conventional anaerobic landfills into biological stabilised state, whereby both current and potential (long-term) emissions of the landfilled waste are mitigated. In recent years, different in situ aeration concepts have been successfullymore » applied in Europe, North America and Asia, all pursuing different objectives and strategies. In Austria, the first full-scale application of in situ landfill aeration by means of low pressure air injection and simultaneous off-gas collection and treatment was implemented on an old, small municipal solid waste (MSW) landfill (2.6 ha) in autumn 2007. Complementary laboratory investigations were conducted with waste samples taken from the landfill site in order to provide more information on the transferability of the results from lab- to full-scale aeration measures. In addition, long-term emission development of the stabilised waste after aeration completion was assessed in an ongoing laboratory experiment. Although the initial waste material was described as mostly stable in terms of the biological parameters gas generation potential over 21 days (GP{sub 21}) and respiration activity over 4 days (RA{sub 4}), the lab-scale experiments indicated that aeration, which led to a significant improvement of leachate quality, was accompanied by further measurable changes in the solid waste material under optimised conditions. Even 75 weeks after aeration completion the leachate, as well as gaseous emissions from the stabilised waste material, remained low and stayed below the authorised Austrian discharge limits. However, the application of in situ aeration at the investigated landfill is a factor 10 behind the lab-based predictions after 3 years of operation, mainly due to technical limitations in the full-scale operation (e.g. high air flow resistivity due to high water content of waste and temporarily high water levels within the landfill; limited efficiency of the aeration wells). In addition, material preparation (e.g. sieving, sorting and homogenisation) prior to the emplacement in Landfill Simulation Reactors (LSRs) must be considered when transferring results from lab- to full-scale application.« less

Pathways of nitrobenzene degradation in horizontal subsurface flow constructed wetlands: Effect of intermittent aeration and glucose addition.

PubMed

Kirui, Wesley K; Wu, Shubiao; Kizito, Simon; Carvalho, Pedro N; Dong, Renjie

2016-01-15

Intermittent aeration and addition of glucose were applied to horizontal subsurface flow constructed wetlands in order to investigate the effect on pathways of nitrobenzene (NB) degradation and interactions with microbial nitrogen and sulphur transformations. The experiment was carried out in three phases A, B and C consisting of different NB loading and glucose dosing. For each phase, the effect of aeration was assessed by intermittently aerating one wetland and leaving one unaerated. Regardless of whether or not the wetland was aerated, at an influent NB concentration of 140 mg/L, both wetlands significantly reduced NB to less than 2 mg/L, a reduction efficiency of 98%. However, once the influent NB concentration was increased to 280 mg/L, the aerated wetland had a higher removal performance 82% compared to that of the unaerated wetland 71%. Addition of glucose further intensified the NB removal to 95% in the aerated wetlands and 92% in the unaerated. Aeration of wetlands enhanced NB degradation, but also resulted in higher NB volatilization of 6 mg m(-2) d(-1). The detected high concentration of sulphide 20-60 mg/L in the unaerated wetland gave a strong indication that NB may act as an electron donor to sulphate-reducing bacteria, but this should be further investigated. Aeration positively improved NB removal in constructed wetlands, but resulted in higher NB volatilization. Glucose addition induced co-metabolism to enhance NB degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Exploration of Near-Field Plume Properties for Aerated-Liquid Jets Using X-Ray Radiography (Postprint)

DTIC Science & Technology

2014-02-01

nozzle exit to discharge more liquid and aerating gas , plume momentum flux increases with liquid flow rate (at the same GLR) in the region...for testing. Water and nitrogen were used as the injectant and aerating gas , respectively. It was demonstrated that the liquid -weighted plume...diameter D2 = throat diameter EPL = equivalent path length GLR = aerating gas -to- liquid mass ratio I = intensity of the transmitted light I0

Effect of aerobic pre-treatment on hydrogen and methane production in a two-stage anaerobic digestion process using food waste with different compositions.

PubMed

Rafieenia, Razieh; Girotto, Francesca; Peng, Wei; Cossu, Raffaello; Pivato, Alberto; Raga, Roberto; Lavagnolo, Maria Cristina

2017-01-01

Aerobic pre-treatment was applied prior to two-stage anaerobic digestion process. Three different food wastes samples, namely carbohydrate rich, protein rich and lipid rich, were prepared as substrates. Effect of aerobic pre-treatment on hydrogen and methane production was studied. Pre-aeration of substrates showed no positive impact on hydrogen production in the first stage. All three categories of pre-aerated food wastes produced less hydrogen compared to samples without pre-aeration. In the second stage, methane production increased for aerated protein rich and carbohydrate rich samples. In addition, the lag phase for carbohydrate rich substrate was shorter for aerated samples. Aerated protein rich substrate yielded the best results among substrates for methane production, with a cumulative production of approximately 351ml/gVS. With regard to non-aerated substrates, lipid rich was the best substrate for CH 4 production (263ml/gVS). Pre-aerated P substrate was the best in terms of total energy generation which amounted to 9.64kJ/gVS. This study revealed aerobic pre-treatment to be a promising option for use in achieving enhanced substrate conversion efficiencies and CH 4 production in a two-stage AD process, particularly when the substrate contains high amounts of proteins. Copyright © 2016 Elsevier Ltd. All rights reserved.

The importance of aeration strategy in fuel alcohol fermentations contaminated with Dekkera/Brettanomyces yeasts.

PubMed

Abbott, D A; Ingledew, W M

2005-11-01

Whole corn mash fermentations infected with industrially-isolated Brettanomyces yeasts were not affected even when viable Brettanomyces yeasts out-numbered Saccharomyces yeasts tenfold at the onset of fermentation. Therefore, aeration, a parameter that is pivotal to the physiology of Dekkera/Brettanomyces yeasts, was investigated in mixed culture fermentations. Results suggest that aeration strategy plays a significant role in Dekkera/Brettanomyces-mediated inhibition of fuel alcohol fermentations. Although growth of Saccharomyces cerevisiae was not impeded, mixed culture fermentations aerated at rates of > or =20 ml air l(-1) mash min(-1) showed decreased ethanol yields and an accumulation of acetic acid. The importance of aeration was examined further in combination with organic acid(s). Growth of Saccharomyces occurred more rapidly than growth of Brettanomyces yeasts in all conditions. The combination of 0.075% (w/v) acetic acid and contamination with Brettanomyces TK 1404W did not negatively impact the final ethanol yield under fermentative conditions. Aeration, however, did prove to be detrimental to final ethanol yields. With the inclusion of aeration in the control condition (no organic acid stress) and in each fermentation containing organic acid(s), the final ethanol yields were decreased. It was therefore concluded that aeration strategy is the key parameter in regards to the negative effects observed in fuel alcohol fermentations infected with Dekkera/Brettanomyces yeasts.

Feasibility study of a passive aeration reactor equipped with vertical pipes for compost stabilization of cow manure.

PubMed

Sylla, Youssouf Boundou; Kuroda, Masao; Yamada, Masayuki; Matsumoto, Naoko

2006-10-01

Pilot-scale composting was carried out with cow manure to evaluate the performances of two passive aeration systems: a conventional passive aeration system equipped with horizontal pipes and an unusual passive aeration method based on air delivery by means of vertical pipes. The effects of both types of passive aeration apparatus were investigated in order to determine the degree of composting rate by continuously monitoring temperature, moisture content, organic matter, electrical conductivity, pH and C/N ratio in the piles. Temperatures in the range of thermophily (55-65 degrees C) were reached in all runs within 1-2 days then lasting for about 1 week, a span long enough for pathogen abatement. Results suggest that passive aeration carried out by vertical pipes is more effective for air delivery into compost piles than conventional passive aeration of air adduction with horizontal pipes. The variation in the number of vertical pipes was revealed to be an important parameter for the control of composting rate and temperature. Composting rates estimated from the heat balance equation were substantially in agreement with those computed through the conversion ratio of total organic matter decrement. The conversion ratios and composting rates obtained in this study using passive aeration with vertical pipes were well aligned with those found using forced air delivery systems.

Aeration of the teuftal landfill: Field scale concept and lab scale simulation.

PubMed

Ritzkowski, Marco; Walker, Beat; Kuchta, Kerstin; Raga, Roberto; Stegmann, Rainer

2016-09-01

Long lasting post-closure care (PCC) is often the major financial burden for operators of municipal solid waste (MSW) landfills. Beside costs for the installation and maintenance of technical equipment and barriers, in particular long term treatment of leachate and landfill gas has to be paid from capital surplus. Estimations based on laboratory experiments project time periods of many decades until leachate quality allows for direct discharge (i.e. no need for further purification). Projections based on leachate samples derived from the last 37years for 35 German landfills confirm these assumption. Moreover, the data illustrate that in particular ammonium nitrogen concentrations are likely to fall below limit values only after a period of 300years. In order to avoid long lasting PCC the operator of Teuftal landfill, located in the Swiss canton Bern, decided to biologically stabilize the landfill by means of a combined in situ aeration and moisturization approach. In December 2014 the aeration started at a landfill section containing approximately 30% of the total landfill volume. From summer 2016 onwards the remaining part of the landfill will be aerated. Landfill aeration through horizontal gas and leachate drains is carried out for the first time in field scale in Europe. The technical concept is described in the paper. Parallel to field scale aeration, investigations for the carbon and nitrogen turnover are carried out by means of both simulated aerated landfills and simulated anaerobic landfills. The results presented in this paper demonstrate that aeration is capable to enhance, both carbon mobilization and discharge via the gas phase. This effect comes along with a significant increase in bio-stabilization of the waste organic fraction, which positively affects the landfill emission behavior in the long run. In terms of leachate pollution reduction it could be demonstrated that the organic load decrease fast and widely independent of the adjusted aeration rates whereby ammonium nitrogen load efficiently decrease later and only under higher aeration rates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nitrogen removal from wastewater by an aerated subsurface-flow constructed wetland in cold climates.

PubMed

Redmond, Eric D; Just, Craig L; Parkin, Gene F

2014-04-01

The objective of this study was to assess the role of cyclic aeration, vegetation, and temperature on nitrogen removal by subsurface-flow engineered wetlands. Aeration was shown to enhance total nitrogen and ammonia removal and to enhance removal of carbonaceous biochemical oxygen demand, chemical oxygen demand, and phosphorus. Effluent ammonia and total nitrogen concentrations were significantly lower in aerated wetland cells when compared with unaerated cells. There was no significant difference in nitrogen removal between planted and unplanted cells. Effluent total nitrogen concentrations ranged from 9 to 12 mg N/L in the aerated cells and from 23 to 24 mg N/L in unaerated cells. Effluent ammonia concentrations ranged from 3 to 7 mg N/L in aerated wetland cells and from 22 to 23 mg N/L in unaerated cells. For the conditions tested, temperature had only a minimal effect on effluent ammonia or total nitrogen concentrations. The tanks-in-series and the PkC models predicted the general trends in effluent ammonia and total nitrogen concentrations, but did not do well predicting short-term variability. Rate coefficients for aerated systems were 2 to 10 times greater than those for unaerated systems.

Enhanced organics and nitrogen removal in batch-operated vertical flow constructed wetlands by combination of intermittent aeration and step feeding strategy.

PubMed

Fan, Jinlin; Liang, Shuang; Zhang, Bo; Zhang, Jian

2013-04-01

Oxygen and carbon source supply are usually insufficient in subsurface flow constructed wetlands. Simultaneous removal of organic pollutants and nitrogen in five batch-operated vertical flow constructed wetlands under different operating conditions was investigated. Alternate aerobic and anaerobic regions were created well with intermittent aeration. Four-month experiments showed that the wetland-applied intermittent aeration combined with step feeding strategy (reactor E) greatly improved the removal of organics, ammonium nitrogen (NH4-N), and total nitrogen (TN) simultaneously, which were 97, 96, and 82%, respectively. It was much better than non-aerated reactors A and B and outperformed intermittently aerated reactor D without step feeding. Continuous aeration (reactor C) significantly enhanced the organics removal and nitrification, but it limited the TN removal (29%) seriously as a result of low denitrification level, and the high operation cost remained a question. The effect of plants was confirmed in this study, and the monitoring data showed that the plants could grow normally. Intermittent aeration as well as step feeding had no obvious influence on the growth of wetland plants in this study.

Accelerated anaerobic hydrolysis rates under a combination of intermittent aeration and anaerobic conditions.

PubMed

Jensen, T R; Lastra Milone, T; Petersen, G; Andersen, H R

2017-04-01

Anaerobic hydrolysis in activated return sludge was investigated in laboratory scale experiments to find if intermittent aeration would accelerate anaerobic hydrolysis rates compared to anaerobic hydrolysis rates under strict anaerobic conditions. The intermittent reactors were set up in a 240 h experiment with intermittent aeration (3 h:3 h) in a period of 24 h followed by a subsequent anaerobic period of 24 h in a cycle of 48 h which was repeated five times during the experiment. The anaerobic reactors were kept under strict anaerobic conditions in the same period (240 h). Two methods for calculating hydrolysis rates based on soluble chemical oxygen demand were compared. Two-way analysis of variance with the Bonferroni post-test was performed in order to register any significant difference between reactors with intermittent aeration and strictly anaerobic conditions respectively. The experiment demonstrated a statistically significant difference in favor of the reactors with intermittent aeration showing a tendency towards accelerated anaerobic hydrolysis rates due to application of intermittent aeration. The conclusion of the work is thus that intermittent aeration applied in the activated return sludge process can improve the treatment capacity further in full scale applications.

Lawson Aerator applications on rangelands

USDA-ARS?s Scientific Manuscript database

Rangeland drills, brush hogs, Dixie harrows, tandem discs and other equipment have played an important role in treating degraded rangeland environments. The Lawson Aerator is one of the newer implements to enter the scene for rangeland improvements. The Lawson Aerator was designed as a pasture renov...

Optimization of micro-aeration intensity in acidogenic reactor of a two-phase anaerobic digester treating food waste.

PubMed

Xu, Suyun; Selvam, Ammaiyappan; Wong, Jonathan W C

2014-02-01

Micro-aeration is known to promote the activities of hydrolytic exo-enzymes and used as a strategy to improve the hydrolysis of particulate substrate. The effect of different micro-aeration rates, 0, 129, 258, and 387 L-air/kg TS/d (denoted as LBR-AN, LBR-6h, LBR-3h and LBR-2h, respectively) on the solubilization of food waste was evaluated at 35°C in four leach bed reactors (LBR) coupled with methanogenic upflow anaerobic sludge blanket (UASB) reactor. Results indicate that the intensity of micro-aeration influenced the hydrolysis and methane yield. Adequate micro-aeration intensity in LBR-3h and LBR-2h significantly enhanced the carbohydrate and protein hydrolysis by 21-27% and 38-64% respectively. Due to the accelerated acidogenesis, more than 3-fold of acetic acid and butyric acid were produced in LBR-3h as compared to the anaerobic treatment LBR-AN resulting in the maximum methane yield of 0.27 L CH4/g VS(added) in the UASB. The performance of LBR-6h with inadequate aeration was similar to that of LBR-AN with a comparable hydrolysis degree. Nevertheless, higher aeration intensity in LBR-2h was also unfavorable for methane yield due to significant biomass generation and CO2 respiration of up to 18.5% and 32.8% of the total soluble hydrolysate, respectively. To conclude, appropriate micro-aeration rate can promote the hydrolysis of solid organic waste and methane yield without undesirable carbon loss and an aeration intensity of 258 L-air/kg TS/d is recommended for acidogenic LBR treating food waste. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effects of caffeine on mitotic index, mitotic aberrations and bimitosis with and without aeration.

PubMed

Röper, W

1977-07-01

The effects of 1 to 3 h 0.2% caffeine treatment on mitosis in lateral roots of Vicia faba with and without aeration have been investigated. During the treatment a marked decrease of the mitotic index followed by strong deviations and changing phase indices can be stated. By means of aeration the number of mitotic aberrations increases with time of treatment, while it decreases without aeration until 3 h treatment. Tetraploid cells are supposed to be formed by spindle aberrations at early anaphase. The number of binucleate and tetraploid cells is affected by aeration during caffeine treatment. During division of the binucleate cells tetraploid nuclei are formed by fusions, so the population of binucleate cells may become smaller.

FOULING OF FINE PORE DIFFUSED AERATORS: AN INTER- PLANT COMPARISON

EPA Science Inventory

There has been increasing interest in fine pore aeration systems, along with concerned about diffuser fouling and the subsequent loss of aeration efficiency. The objective of this study was to assess the relative fouling tendency of fine bubble diffusers t nine activated sludge ...

Aerated biofilters with multiple-level air injection configurations to enhance biological treatment of methane emissions.

PubMed

Farrokhzadeh, Hasti; Hettiaratchi, J Patrick A; Jayasinghe, Poornima; Kumar, Sunil

2017-09-01

Aiming to improve conventional methane biofilter performance, a multiple-level aeration biofilter design is proposed. Laboratory flow-through column experiments were conducted to evaluate three actively-aerated methane biofilter configurations. Columns were aerated at one, two, and three levels of the bed depth, with air introduced at flow rates calculated from methane oxidation reaction stoichiometry. Inlet methane loading rates were increased in five stages between 6 and 18mL/min. The effects of methane feeding rate, levels of aeration, and residence time on methane oxidation rates were determined. Samples collected after completion of flow-through experiments were used to determine methane oxidation kinetic parameters, V max , K m , and methanotrophic community distribution across biofilter columns. Results obtained from mixed variances analysis and response surfaces, as well as methanotrophic activity data, suggested that, biofilter column with two aeration levels has the most even performance over time, maintaining 85.1% average oxidation efficiency over 95days of experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Achieving ethanol-type fermentation for hydrogen production in a granular sludge system by aeration.

PubMed

Zhang, Song; Liu, Min; Chen, Ying; Pan, Yu-Ting

2017-01-01

To investigate the effects of aeration on hydrogen-producing granular system, experiments were performed in two laboratory-scale anaerobic internal circulation hydrogen production (AICHP) reactors. The preliminary experiment of Reactor 1 showed that direct aeration was beneficial to enhancing hydrogen production. After the direct aeration was implied in Reactor 2, hydrogen production rate (HPR) and hydrogen content were increased by 100% and 60%, respectively. In addition, mixed-acid fermentation was transformed into typical ethanol-type fermentation (ETF). Illumina MiSeq sequencing shows that the direct aeration did not change the species of hydrogen-producing bacteria but altered their abundance. Hydrogen-producing bacteria and ethanol-type fermentative bacteria were increased by 24.5% and 146.3%, respectively. Ethanoligenens sp. sharply increased by 162.2% and turned into predominant bacteria in the system. These findings indicated that appropriate direct aeration might be a novel and promising way to obtain ETF and enhance hydrogen production in practical use. Copyright © 2016 Elsevier Ltd. All rights reserved.

Reducing aeration energy consumption in a large-scale membrane bioreactor: Process simulation and engineering application.

PubMed

Sun, Jianyu; Liang, Peng; Yan, Xiaoxu; Zuo, Kuichang; Xiao, Kang; Xia, Junlin; Qiu, Yong; Wu, Qing; Wu, Shijia; Huang, Xia; Qi, Meng; Wen, Xianghua

2016-04-15

Reducing the energy consumption of membrane bioreactors (MBRs) is highly important for their wider application in wastewater treatment engineering. Of particular significance is reducing aeration in aerobic tanks to reduce the overall energy consumption. This study proposed an in situ ammonia-N-based feedback control strategy for aeration in aerobic tanks; this was tested via model simulation and through a large-scale (50,000 m(3)/d) engineering application. A full-scale MBR model was developed based on the activated sludge model (ASM) and was calibrated to the actual MBR. The aeration control strategy took the form of a two-step cascaded proportion-integration (PI) feedback algorithm. Algorithmic parameters were optimized via model simulation. The strategy achieved real-time adjustment of aeration amounts based on feedback from effluent quality (i.e., ammonia-N). The effectiveness of the strategy was evaluated through both the model platform and the full-scale engineering application. In the former, the aeration flow rate was reduced by 15-20%. In the engineering application, the aeration flow rate was reduced by 20%, and overall specific energy consumption correspondingly reduced by 4% to 0.45 kWh/m(3)-effluent, using the present practice of regulating the angle of guide vanes of fixed-frequency blowers. Potential energy savings are expected to be higher for MBRs with variable-frequency blowers. This study indicated that the ammonia-N-based aeration control strategy holds promise for application in full-scale MBRs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of aeration on matrix temperature by infrared thermal imager and computational fluid dynamics during sludge bio-drying.

PubMed

Yu, Dawei; Yang, Min; Qi, Lu; Liu, Mengmeng; Wang, Yawei; Wei, Yuansong

2017-10-01

The effect of aeration on the pile matrix temperature was investigated using thermocouples and Infrared Thermal Imager (IRI) for temperature sensing, and Computational Fluid Dynamics (CFD) for modelling of temperature variation during aeration in a full-scale sludge biodrying plant. With aeration saving of 20%, the improved strategy speeded up biodrying from 21 days to 14 days, while achieving similar drying effect. A persistent thermocouple recorded the one-dimensional (1D) total temperature variation of all aeration strategies. The IRI captured the rapid two-dimensional (2D) pile temperature dropped from 72.5 °C to 30.3 °C during 6 min of aeration, which mechanism suggested as the latent heat of moisture evaporation and sensible heat of air exchange. The CFD three-dimensional (3D) CFD results highlight the importance of latent heat rather than sensible heat. Therefore, the pile temperature drop inferred is ΔT = 5.38 °C theoretically and ΔT = 5.17 ± 4.56 °C practically, per unit of MC removed. These findings also emphasize the possibility of a pile temperature valley, due to excessive aeration under unsaturated vapour conditions. Surface temperature monitored by IRI coupled with 3D temperature simulated by CFD rapidly gives a clear matrix temperature evolution, empowering biodrying by more accurate temperature and aeration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Luffa sponge offsets the negative effects of aeration on bacterial cellulose production.

PubMed

Krusong, W; Kerdpiboon, S; Pornpukdeewattana, S; Jindaprasert, A

2016-12-01

To offset the negative effects of aeration on bacterial cellulose (BC) production by acetic acid bacteria using enmeshed cellulose microfibrils (CM) on luffa sponge matrices (LSM). The CM were enmeshed on LSM (LSM-CM). The optimal amount of LSM-CM was determined for BC production under aerated conditions. Without LSM-CM, no BC was produced in seven out of nine production cycles at the highest aeration rate (9 l min -1 ). However, with 0·5% LSM-CM and an aeration rate of 3 l min -1 , a satisfactory oxygen transfer coefficient was achieved, and also a good yield of BC (5·24 g l -1 ). Moreover, the LSM-CM was able to be recycled through nine consecutive BC production cycles. The highest BC yields (from 5·8 ± 0·4 to 6·6 ± 0·4 g l -1 ) were associated with high bacterial biomass and this was confirmed by scanning electron microscopy. We confirm that LSM-CM works well as a starter. Microenvironments low in dissolved oxygen within the matrices of LSM-CM are important for BC production under aeration conditions. The LSM-CM provides a microenvironment which offsets the negative effects of aeration on BC production. A sustainable, economic process for mass BC production is described using recycled LSM-CM with aeration. © 2016 The Society for Applied Microbiology.

Pilot plant demonstration of stable and efficient high rate biological nutrient removal with low dissolved oxygen conditions.

PubMed

Keene, Natalie A; Reusser, Steve R; Scarborough, Matthew J; Grooms, Alan L; Seib, Matt; Santo Domingo, Jorge; Noguera, Daniel R

2017-09-15

Aeration in biological nutrient removal (BNR) processes accounts for nearly half of the total electricity costs at many wastewater treatment plants. Even though conventional BNR processes are usually operated to have aerated zones with high dissolved oxygen (DO) concentrations, recent research has shown that nitrification can be maintained using very low-DO concentrations (e.g., below 0.2 mg O 2 /L), and therefore, it may be possible to reduce energy use and costs in BNR facilities by decreasing aeration. However, the effect of reduced aeration on enhanced biological phosphorus removal (EBPR) is not understood. In this study, we investigated, at the pilot-scale level, the effect of using minimal aeration on the performance of an EBPR process. Over a 16-month operational period, we performed stepwise decreases in aeration, reaching an average DO concentration of 0.33 mg O 2 /L with stable operation and nearly 90% phosphorus removal. Under these low-DO conditions, nitrification efficiency was maintained, and nearly 70% of the nitrogen was denitrified, without the need for internal recycling of high nitrate aeration basin effluent to the anoxic zone. At the lowest DO conditions used, we estimate a 25% reduction in energy use for aeration compared to conventional BNR operation. Our improved understanding of the efficiency of low-DO BNR contributes to the global goal of reducing energy consumption during wastewater treatment operations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Aerated Shewanella oneidensis in Continuously-fed Bioelectrochemical Systems for Power and Hydrogen Production

USDA-ARS?s Scientific Manuscript database

We studied the effects of aeration of Shewanella oneidensis on potentiostatic current production, iron(III) reduction, hydrogen production in a microbial electrolysis cell, and electric power generation in a microbial fuel cell. The potentiostatic performance of aerated S. oneidensis was considerab...

OXIDATION OF AS(III) BY AERATION AND STORAGE

EPA Science Inventory

A study of the effects of aeration and storage on the oxidation of arsenic(III) was undertaken at three utilities in the US to establish the engineering significance of aeration as a potential pre-treatment method for arsenic removal. The results of this study clearly establish t...

21 CFR 880.6100 - Ethylene oxide gas aerator cabinet.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ethylene oxide gas aerator cabinet. 880.6100... Miscellaneous Devices § 880.6100 Ethylene oxide gas aerator cabinet. (a) Identification. An ethyene oxide gas... required to remove residual ethylene oxide (ETO) from wrapped medical devices that have undergone ETO...

Research About the Corosive Effects of FeCl3 in the Aeration Wastewater Basin

NASA Astrophysics Data System (ADS)

Panaitescu, C.; Petrescu, M. G.

2018-01-01

Biological aeration of industrial wastewater is a very impressive process in the treatment of wastewater. The involvement of chemical reagents in this process, however, implies the intensification of the corrosion processes due to both pollutants in the wastewater and the chemical reactions that occur when the coagulation / flocculation reagents are added. This paper explores the action of ferric chloride (FeCl3) on metallic parts in the aeration basin. The most affected structures are metal. At the classical basins the aeration systems were made of P295GH materials. The corrosion produced is uneven. The analysis of the high degree of corrosion was done according to the national and international standards. Finally, the paper supports the replacement of the existing aeration system with an anticorrosive material.

Bioreactor tests preliminary to landfill in situ aeration: a case study.

PubMed

Raga, Roberto; Cossu, Raffaello

2013-04-01

Lab scale tests in bioreactor were carried out in the framework of the characterization studies of a landfill where in situ aeration (possibly followed by landfill mining) had been proposed as part of the novel waste management strategy in a region in northern Italy. The tests were run to monitor the effects produced by aerobic conditions at different temperatures on waste sampled at different depths in the landfill, with focus on the carbon and nitrogen conversion during aeration. Temperatures ranging from 35 to 45°C were chosen, in order to evaluate possible inhibition of biodegradation processes (namely nitrification) at 45°C in the landfill. The results obtained showed positive effects of the aeration on leachate quality and a significant reduction of waste biodegradability. Although a delay of biodegradation processes was observed in the reactor run at 45°C, biodegradation rates increased after 2 months of aeration, providing very low values of the relevant parameters (as in the other aerated reactors) by the end of the study. Mass balances were carried out for TOC and NNH4(+); the findings obtained were encouraging and provided evidence of the effectiveness of carbon and nitrogen conversion processes in the aerated landfill simulation reactors. Copyright © 2012 Elsevier Ltd. All rights reserved.

The effect of aeration on the removal of wastewater-derived pharmaceutical residues from groundwater - a laboratory study.

PubMed

Burke, Victoria; Duennbier, Uwe; Massmann, Gudrun

2013-01-01

Several studies on waste- or drinking water treatment processes as well as on groundwater have recently shown that some pharmaceutical residues (PRs) are redox-sensitive. Hence, their (bio)degradation depends on the redox conditions prevalent in the aquifer. Groundwater, providing raw water for drinking water production, is often anoxic and aeration is a widespread treatment method applied mainly to eliminate unwanted iron and manganese from the water. As a side-effect, aeration may trigger the elimination of PRs. Within the present study the influence of aeration on the fate of a number of wastewater derived analgesics and their residues as well as several antimicrobial compounds was investigated. For this purpose, anoxic groundwater was transferred into stainless steel tanks, some of which were aerated while others were continuously kept anoxic. Results prove that the degradation of six phenazone type compounds is dependent on oxygen availability and compounds are efficiently removed under oxic conditions only. Concerning the antimicrobials, doxycycline and trimethoprim were better removed during aeration, whereas a slightly improved removal under anoxic conditions was observed for clindamycin, roxithromycin and clarithromycin. The study provides first laboratory proof of the redox-sensitivity of several organic trace pollutants. In addition, results demonstrate that aeration is an effective treatment for the elimination of a number of wastewater derived PRs.

Microalgae population dynamics in photobioreactors with secondary sewage effluent as culture medium

PubMed Central

Marchello, Adriano E.; Lombardi, Ana T.; Dellamano-Oliveira, Maria José; de Souza, Clovis W.O.

2015-01-01

Nitrogen and phosphorus present in sewage can be used for microalgae growth, possibiliting cost reduction in the production of microalgae at the same time that it decreases the eutrophication potential of the effluent. This research aimed at monitoring the native community of microalgae and coliform bacteria in a secondary effluent from anaerobic municipal sewage treatment. Two treatments (aerated and non-aerated) were performed to grow microalgae under semi-controlled conditions in semi-closed photobioreactors in a greenhouse. The results showed no significant pH and coliforms (total and Escherichia coli ) variation between treatments. Nutrient concentrations were reduced supporting microalgae growth up to 10 7 cells.mL −1 independent of aeration. Exponential growth was obtained from the first day for the non-aerated, but a 5 day lag phase of growth was obtained for the aerated. Chlorella vulgaris was the dominant microalgae (99.9%) in both treatments. In the aerated, 5 algae classes were detected (Chlorophyceae, Cyanophyceae, Chrysophyceae, Bacillariophyceae and Euglenophyceae), with 12 taxa, whereas in the non-aerated, 2 classes were identified (Chlorophyceae and Cyanophyceae), with 5 taxa. We concluded that effluent is viable for microalgae growth, especially Chlorella vulgaris, at the same time that the eutrophication potential and coliforms are decreased, contributing for better quality of the final effluent. PMID:26221091

New jet-aeration system using 'Supercavitation'.

PubMed

Schmid, Andreas

2010-03-01

A newly developed fine bubble aeration system, by which air is transferred under supercavitation conditions, shows a clearly better performance than traditional, well-known aerators that rely on the jet-pump principle and its performance can be compared to oxygen transfer rates achieved in membrane and foil plate aerators. A prototype supercavitation aerator installed at a sewage treatment plant revealed an air input rate, which was about one third lower than that of the jet-pump system, which it replaced. In spite of this low air input rate, the daily demand of pure oxygen for the additionally installed membrane aeration system went down by approximately 49%, from the original level of about 1,200 m(3)/day to about 600 m(3)/day-and this over a test period of more than 7 months. The observed high oxygen transfer rates cannot be explained by traditional mass transfer mechanisms. It is assumed that a large amount of water being transferred into the gas phase by supercavitation contacting directly oxygen also in the gas phase and thereby overcoming mass transfer hindrances which might be favoured by hydroxyl radicals. With this new aerator, during the first 3 months of test phase, already more than 10,000 Euros had been saved because of the reduced pure oxygen demand.

Effect of intermittent aeration strategies on treatment performance and microbial community of an IFAS reactor treating municipal waste water.

PubMed

Singh, Nitin Kumar; Bhatia, Akansha; Kazmi, Absar Ahmad

2017-11-01

This study investigated the effect of various intermittent aeration (IA) cycles on organics and nutrient removal, and microbial communities in an integrated fixed-film activated sludge (IFAS) reactor treating municipal waste water. Average effluent biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids, total nitrogen (TN) and total phosphorus (TP) values were noted as 20, 50, 30, 12 and 1.5 mgL -1 , respectively, in continuous aeration mode. A total of four operational conditions (run 1, continuous aeration; run 2, 150/30 min aeration on/off time; run 3, 120/60 min aeration on/off time and run 4, 90/60 min aeration on/off time) were investigated in IFAS reactor assessment. Among the all examined IA cycles, IA phase 2 gave the maximum COD and BOD removals with values recorded as 97% and 93.8%, respectively. With respect to nutrient removal (TN and TP), IA phase 1 was found to be optimum. Pathogen removal efficiency of present system was recorded as 90-95% during the three phases. With regard to settling characteristics, pilot showed poor settling during IA schedules, which was also evidenced by high sludge volume index values. Overall, IA could be used as a feasible way to improve the overall performance of IFAS system.

Photosynthetic aeration in biological wastewater treatment using immobilized microalgae-bacteria symbiosis.

PubMed

Praveen, Prashant; Loh, Kai-Chee

2015-12-01

Chlorella vulgaris encapsulated in alginate beads were added into a bioreactor treating synthetic wastewater using Pseudomonas putida. A symbiotic CO2/O2 gas exchange was established between the two microorganisms for photosynthetic aeration of wastewater. During batch operation, glucose removal efficiency in the bioreactor improved from 50% in 12 h without aeration to 100% in 6 h, when the bioreactor was aerated photosynthetically. During continuous operation, the bioreactor was operated at a low hydraulic retention time of 3.3 h at feed concentrations of 250 and 500 mg/L glucose. The removal efficiency at 500 mg/L increased from 73% without aeration to 100% in the presence of immobilized microalgae. The initial microalgae concentration was critical to achieve adequate aeration, and the removal rate increased with increasing microalgae concentration. The highest removal rate of 142 mg/L-h glucose was achieved at an initial microalgae concentration of 190 mg/L. Quantification of microalgae growth in the alginate beads indicated an exponential growth during symbiosis, indicating that the bioreactor performance was limited by oxygen production rates. Under symbiotic conditions, the chlorophyll content of the immobilized microalgae increased by more than 30%. These results indicate that immobilized microalgae in symbiosis with heterotrophic bacteria are promising in wastewater aeration.

3-D Numerical Simulation for Gas-Liquid Two-Phase Flow in Aeration Tank

NASA Astrophysics Data System (ADS)

Xue, R.; Tian, R.; Yan, S. Y.; Li, S.

In the crafts of activated sludge treatment, oxygen supply and the suspending state of activated sludge are primary factors to keep biochemistry process carrying on normally. However, they are all controlled by aeration. So aeration is crucial. The paper focus on aeration, use CFD software to simulate the field of aeration tank which is designed by sludge load method. The main designed size of aeration tank is: total volume: 20 000 m3; corridor width: 8m; total length of corridors: 139m; number of corridors: 3; length of one single corridor: 48m; effective depth: 4.5m; additional depth: 0.5m. According to the similarity theory, a geometrical model is set up in proportion of 10:1. The way of liquid flow is submerge to avoid liquid flow out directly. The grid is plotted by dividing the whole computational area into two parts. The bottom part which contains gas pipe and gas exit hole and the above part which is the main area are plotted by tetrahedron and hexahedron respectively. In boundary conditions, gas is defined as the primary-phase, and liquid is defined as the secondary-phase. Choosing mixture model, two-phase flow field of aeration tank is simulated by solved the Continuity equation for the mixture, Momentum equation for the mixture, Volume fraction equation for the secondary phases and Relative velocity formula when gas velocity is 10m/s, 20m/s, 30m/s. what figure shows is the contour of velocity magnitude for the mixture phase when gas velocity is 20m/s. Through analysis, the simulation tendency is agreed with actual running of aeration tank. It is feasible to use mixture model to simulate flow field of aeration tank by fluent software. According to the simulation result, the better velocity of liquid or gas (the quantity of inlet air) can be chosen by lower cost, and also the performance of aeration tank can be forecast. It will be helpful for designing and operation.

Effects of intermittent and continuous aeration on accelerative stabilization and microbial population dynamics in landfill bioreactors.

PubMed

Sang, Nguyen Nhu; Soda, Satoshi; Inoue, Daisuke; Sei, Kazunari; Ike, Michihiko

2009-10-01

Performance and microbial population dynamics in landfill bioreactors were investigated in laboratory experiments. Three reactors were operated without aeration (control reactor, CR), with cyclic 6-h aeration and 6-h non-aeration (intermittently aerated reactor, IAR), and with continuous aeration (continuously aerated reactor, CAR). Each reactor was loaded with high-organic solid waste. The performance of IAR was highest among the reactors up to day 90. The respective solid weight, organic matter content, and waste volume on day 90 in the CR, IAR, and CAR were 50.9, 39.1, and 47.5%; 46.5, 29.3 and 35.0%; and 69, 38, and 53% of the initial values. Organic carbon and nitrogen compounds in leachate in the IAR and the CAR showed significant decreases in comparison to those in the CR. The most probable number (MPN) values of fungal 18S rDNA in the CAR and the IAR were higher than those in the CR. Terminal restriction fragment length polymorphism analysis showed that unique and diverse eubacterial and archaeal communities were formed in the IAR. The intermittent aeration strategy was favorable for initiation of solubilization of organic matter by the aerobic fungal populations and the reduction of the acid formation phase. Then the anaerobic H(2)-producing bacteria Clostridium became dominant in the IAR. Sulfate-reducing bacteria, which cannot use acetate/sulfate but which instead use various organics/sulfate as the electron donor/acceptor were also dominant in the IAR. Consequently, Methanosarcinales, which are acetate-utilizing methanogens, became the dominant archaea in the IAR, where high methane production was observed.

PIV Study of Aeration Efficient of Stepped Spillway System

NASA Astrophysics Data System (ADS)

Abas, M. A.; Jamil, R.; Rozainy, M. R.; Zainol, M. A.; Adlan, M. N.; Keong, C. W.

2017-06-01

This paper investigates the three-dimensional (3D) simulation of Cascade aerator system using Lattice Boltzmann simulation and laboratory experiment was carried out to investigate the flow, aeration and cavitation in the spillway. Different configurations of stepped spillway are designed in this project in order to investigate the relationship between the configurations of stepped spillway and cavitation in the flow. The aeration in the stepped spillway will also be investigated. The experimental result will be compared with the simulated result at the end of this project. The figure of flow pattern at the 3rd step in simulation and experiment for Set 1 and Set 2 are look similar between LBM simulation and the experiment findings. This will provide a better understanding of the cavitation, aeration and flow in different configurations of the stepped spillway. In addition the occurrence of negative pressure region in the stepped spillway, increases the possibility of cavitation to occur. The cavitation will damage the structure of the stepped spillway. Furthermore, it also founds that increasing in barrier thickness of the stepped spillway will improve the aeration efficiency and reduce the cavitation in stepped spillway.

Simultaneous removal of organic matter and salt ions from coal gasification wastewater RO concentrate and microorganisms succession in a MBR.

PubMed

Jia, Shengyong; Han, Yuxing; Zhuang, Haifeng; Han, Hongjun; Li, Kun

2017-10-01

A lab-scale membrane bioreactor (MBR) with intermittent aeration was operated to treat the reverse osmosis concentrate derived from coal gasification wastewater. Results showed intermittent aeration represented slight effect on organic matter reduction but significant effect on nitrite and nitrate reduction, with 6h aeration and 6h non-aeration, removal efficiencies of organic matter, chloride, sulfate, nitrite and nitrate reached 48.35%, 40.91%, 34.28%, -36.05% and 64.34%, respectively. High-throughput sequencing showed a microorganisms succession from inoculated activated sludge (S1) to activated sludge in MBR (S2) with high salinity. Richness and diversity of microorganisms in S2 was lower than S1 and the community structure of S1 exhibited more even than S2. The most relative abundance of genus in S1 and S2 were unclassified_Desulfarculaceae (9.39%) and Roseibaca (62.1%), respectively. High salinity and intermittent aeration represented different influence on the denitrifying genus, and non-aeration phase provided feasible dissolved oxygen condition for denitrifying genera realizing denitrification. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chemical Oxygen Demand abatement in sewage using Micro-Aeration Enhanced Ecological Floating Bed

NASA Astrophysics Data System (ADS)

Shi, Hongle; Zhou, Gaofeng; Liu, Yiqing; Tan, Jiancong; Fu, Yongsheng

2018-02-01

The traditional ecological floating bed combined with micro-aeration system and artificial medium was developed for the removal of contaminants and remediation of surface water. This micro-aeration enhanced ecological floating bed (MAEEFB) consisted of aeration unit, microbial processing unit and aquatic plant unit. Batch experiments were conducted in different operating conditions on the removal of chemical oxygen demand (COD) in the sewage using MAEEFB. The removal rate of COD by MAEEFB, enhanced ecological floating bed (EEFB) and traditional ecological floating bed (TEFB) in the same reaction conditions was 59.2%, 56.9% and 30.6%, respectively, indicating that the combination of micro-aeration system and artificial medium could enhance the removal efficiency of COD in TEFB. In MAEEFB, the aeration intensity should be designed reasonablely considering both treatment efficiency and operation cost. Only increasing the specific surface area of the packing cannot effectively improve the purification efficiency of water. Factors like packing material, ability of intercepting organics and complicated extent of microorganisms attaching on the packing should also be considered.

Pathway governing nitrogen removal in artificially aerated constructed wetlands: Impact of aeration mode and influent chemical oxygen demand to nitrogen ratios.

PubMed

Hou, Jie; Wang, Xin; Wang, Jie; Xia, Ling; Zhang, Yiqing; Li, Dapeng; Ma, Xufa

2018-06-01

This study aimed at assessing the influence of aeration mode and influent COD/N ratio on nitrogen removal in constructed wetlands (CWs). The results showed that a simultaneous partial nitrification, anammox and denitrification (SNAD) process was established in the intermittent aerated V1. While nitrogen removal pathway gradually changed from partial nitrification-denitrification to complete nitrification-denitrification along with reducing COD/N ratio in the continuous limited aerated V2. Effective inhibition of NOBs under intermittent aeration conditions, good retention of anammox bacteria biomass and much faster depletion of COD prior to substantial NH 4 + -N conversion jointly led to the successful achievement of stable SNDA process with elevated influent COD/N ratios in V1. Furthermore, the presence of SNAD ensured a robust ammonium (84-92%) and TN (80-91%) removal efficiency in V1 under varying COD loading rates. In contrast, the TN removal efficiency decreased rapidly along with the reducing influent COD/N ratios in V2. Copyright © 2018 Elsevier Ltd. All rights reserved.

Aeration strategy for biofilm cultivation of the microalga Scenedesmus dimorphus.

PubMed

Ji, Chunli; Wang, Junfeng; Liu, Tianzhong

2015-10-01

Biofilm cultivation of microalgae may be useful for biofuel production. However, many aspects for this cultivation method have not been well assessed. Accordingly, aeration strategy for biofilm cultivation of Scenedesmus dimorphus has been explored. Biomass, lipid and triacylglycerol (TAG) productivity in increased S. dimorphus as the CO2 concentration increased within 0.038-0.5% and kept constant with further increases. The biomass, lipid and TAG productivity increased with the speed increasing and an obvious threshold point was observed at 6.6 ml(-2) min(-1). The lipid and TAG content was unaffected by the aeration rate. Both the CO2 concentration as well as aeration speed affected the growth of S. dimorphus in biofilm cultivation. The optimized aeration strategy for biofilm cultivation was continuous air flow enriched with 1% CO2 (v/v) at 6.6 ml(-2) min(-1).

Ventilatory protective strategies during thoracic surgery: effects of alveolar recruitment maneuver and low-tidal volume ventilation on lung density distribution.

PubMed

Kozian, Alf; Schilling, Thomas; Schütze, Hartmut; Senturk, Mert; Hachenberg, Thomas; Hedenstierna, Göran

2011-05-01

The increased tidal volume (V(T)) applied to the ventilated lung during one-lung ventilation (OLV) enhances cyclic alveolar recruitment and mechanical stress. It is unknown whether alveolar recruitment maneuvers (ARMs) and reduced V(T) may influence tidal recruitment and lung density. Therefore, the effects of ARM and OLV with different V(T) on pulmonary gas/tissue distribution are examined. Eight anesthetized piglets were mechanically ventilated (V(T) = 10 ml/kg). A defined ARM was applied to the whole lung (40 cm H(2)O for 10 s). Spiral computed tomographic lung scans were acquired before and after ARM. Thereafter, the lungs were separated with an endobronchial blocker. The pigs were randomized to receive OLV in the dependent lung with a V(T) of either 5 or 10 ml/kg. Computed tomography was repeated during and after OLV. The voxels were categorized by density intervals (i.e., atelectasis, poorly aerated, normally aerated, or overaerated). Tidal recruitment was defined as the addition of gas to collapsed lung regions. The dependent lung contained atelectatic (56 ± 10 ml), poorly aerated (183 ± 10 ml), and normally aerated (187 ± 29 ml) regions before ARM. After ARM, lung volume and aeration increased (426 ± 35 vs. 526 ± 69 ml). Respiratory compliance enhanced, and tidal recruitment decreased (95% vs. 79% of the whole end-expiratory lung volume). OLV with 10 ml/kg further increased aeration (atelectasis, 15 ± 2 ml; poorly aerated, 94 ± 24 ml; normally aerated, 580 ± 98 ml) and tidal recruitment (81% of the dependent lung). OLV with 5 ml/kg did not affect tidal recruitment or lung density distribution. (Data are given as mean ± SD.) The ARM improves aeration and respiratory mechanics. In contrast to OLV with high V(T), OLV with reduced V(T) does not reinforce tidal recruitment, indicating decreased mechanical stress.

The use of an aeration system to prevent thermal stratification of a freshwater impoundment and its effect on downstream fish assemblages.

PubMed

Miles, N G; West, R J

2011-03-01

Warm-water riverine fish assemblages were investigated downstream of an impoundment before and after thermal stratification and the associated cold-water pollution was prevented using an aeration system. Temperatures below the dam significantly increased after installation of the aeration system and this correlated with an increased abundance and greater number of species downstream. Overall, aeration appeared to be beneficial for both the lake (upstream) and the downstream riverine environments. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

An aeration control strategy for oxidation ditch processes based on online oxygen requirement estimation.

PubMed

Zhan, J X; Ikehata, M; Mayuzumi, M; Koizumi, E; Kawaguchi, Y; Hashimoto, T

2013-01-01

A feedforward-feedback aeration control strategy based on online oxygen requirements (OR) estimation is proposed for oxidation ditch (OD) processes, and it is further developed for intermittent aeration OD processes, which are the most popular type in Japan. For calculating OR, concentrations of influent biochemical oxygen demand (BOD) and total Kjeldahl nitrogen (TKN) are estimated online by the measurement of suspended solids (SS) and sometimes TKN is estimated by NH4-N. Mixed liquor suspended solids (MLSS) and temperature are used to estimate the required oxygen for endogenous respiration. A straightforward parameter named aeration coefficient, Ka, is introduced as the only parameter that can be tuned automatically by feedback control or manually by the operators. Simulation with an activated sludge model was performed in comparison to fixed-interval aeration and satisfying result of OR control strategy was obtained. The OR control strategy has been implemented at seven full-scale OD plants and improvements in nitrogen removal are obtained in all these plants. Among them, the results obtained in Yumoto wastewater treatment plant were presented, in which continuous aeration was applied previously. After implementing intermittent OR control, the total nitrogen concentration was reduced from more than 5 mg/L to under 2 mg/L, and the electricity consumption was reduced by 61.2% for aeration or 21.5% for the whole plant.

Increased Production of Hydrogen Peroxide by Lactobacillus delbrueckii subsp. bulgaricus upon Aeration: Involvement of an NADH Oxidase in Oxidative Stress

PubMed Central

Marty-Teysset, C.; de la Torre, F.; Garel, J.-R.

2000-01-01

The growth of Lactobacillus delbrueckii subsp. bulgaricus (L. delbrueckii subsp. bulgaricus) on lactose was altered upon aerating the cultures by agitation. Aeration caused the bacteria to enter early into stationary phase, thus reducing markedly the biomass production but without modifying the maximum growth rate. The early entry into stationary phase of aerated cultures was probably related to the accumulation of hydrogen peroxide in the medium. Indeed, the concentration of hydrogen peroxide in aerated cultures was two to three times higher than in unaerated ones. Also, a similar shift from exponential to stationary phase could be induced in unaerated cultures by adding increasing concentrations of hydrogen peroxide. A significant fraction of the hydrogen peroxide produced by L. delbrueckii subsp. bulgaricus originated from the reduction of molecular oxygen by NADH catalyzed by an NADH:H2O2 oxidase. The specific activity of this NADH oxidase was the same in aerated and unaerated cultures, suggesting that the amount of this enzyme was not directly regulated by oxygen. Aeration did not change the homolactic character of lactose fermentation by L. delbrueckii subsp. bulgaricus and most of the NADH was reoxidized by lactate dehydrogenase with pyruvate. This indicated that NADH oxidase had no (or a very small) energetic role and could be involved in eliminating oxygen. PMID:10618234

Optimum aerobic volume control based on continuous in-line oxygen uptake monitoring.

PubMed

Svardal, K; Lindtner, S; Winkler, S

2003-01-01

Dynamic adaptation of the aerated volume to changing load conditions is essential to maximise the nitrogen removal performance and to minimise energy consumption. A control strategy is presented which provides optimum aerobic volume control (OAV-control concept) based on continuous in-line oxygen uptake monitoring. For ammonium concentrations below 1 mg/l the oxygen uptake rate shows a strong and almost linear dependency on the ammonium concentration. Therefore, the oxygen uptake rate is an ideal indicator for the nitrification performance in activated sludge systems. The OAV-control concept provides dynamic variation of the minimum aerobic volume required for complete nitrification and therefore maximises the denitrification performance. In-line oxygen uptake monitoring is carried out by controlling the oxygen concentration in a continuous aerated zone of the aeration tank and measuring the total air flow to the aeration tank. The total air flow to the aeration tank is directly proportional to the current oxygen uptake rate and can therefore be used as an indicator for the required aerobic volume. The instrumentation requirements for installation of the OAV-control are relatively low, oxygen sensors in the aeration tank and an on-line air flow measurement are needed. This enables individual control of aeration tanks operated in parallel at low investment costs. The OAV-control concept is installed at the WWTP Linz-Asten (1 Mio PE) and shows very good results. Full scale results are presented.

Methanogenesis acceleration of fresh landfilled waste by micro-aeration.

PubMed

Shao, Li-Ming; He, Pin-Jing; Zhang, Hua; Yu, Xiao-Hua; Li, Guo-Jian

2005-01-01

When municipal solid waste (MSW) with high content of food waste is landfilled, the rapid hydrolysis of food waste results in the imbalance of anaerobic metabolism in the landfill layer, indicated by accumulation of volatile fatty acids (VFA) and decrease of pH value. This occurrence could lead to long lag time before the initiation of methanogenesis and to the production of strong leachate. Simulated landfill columns with forced aeration, with natural ventilation, and with no aeration, were monitored regarding their organics degradation rate with leachate recirculation. Hydrolysis reactions produced strong leachate in the column with no aeration. With forced aeration, the produced VFA could be effectively degraded, leading to the reduction in COD of the leachate effluent since the week 3. The CH4 in the landfill gas from the column with aeration rate of 0.39 m3/(m3 x d) and frequency of twice/d, leachate recirculation rate of 12.2 mm/d and frequency of twice/d, could amount to 40% (v/v) after only 20 weeks. This amount had increased up to 50% afterward even with no aeration. Most of COD in the recirculated leachate was removed. Using natural ventilation, CH4 could also be produced and the COD of the leachate effluent be reduced after 10 weeks of operation. However, the persistent existence of oxygen in the landfill layer yielded instability in methanogenesis process.

Generating CO(2)-credits through landfill in situ aeration.

PubMed

Ritzkowski, M; Stegmann, R

2010-04-01

Landfills are some of the major anthropogenic sources of methane emissions worldwide. The installation and operation of gas extraction systems for many landfills in Europe and the US, often including technical installations for energy recovery, significantly reduced these emissions during the last decades. Residual landfill gas, however, is still continuously produced after the energy recovery became economically unattractive, thus resulting in ongoing methane emissions for many years. By landfill in situ aeration these methane emissions can be widely avoided both, during the aeration process as well as in the subsequent aftercare period. Based on model calculations and online monitoring data the amount of avoided CO(2-eq). can be determined. For an in situ aerated landfill in northern Germany, acting as a case study, 83-95% (depending on the kind and quality of top cover) of the greenhouse gas emission potential could be reduced under strictly controlled conditions. Recently the United Nations Framework Convention on Climate Change (UNFCCC) has approved a new methodology on the "Avoidance of landfill gas emissions by in situ aeration of landfills" (UNFCCC, 2009). Based on this methodology landfill aeration projects might be considered for generation of Certified Emission Reductions (CERs) in the course of CDM projects. This paper contributes towards an evaluation of the potential of landfill aeration for methane emissions reduction. Copyright 2009 Elsevier Ltd. All rights reserved.

Ecophysiology of wetland plant roots: A modelling comparison of aeration in relation to species distribution

USGS Publications Warehouse

Sorrell, B.K.; Mendelssohn, I.A.; McKee, K.L.; Woods, R.A.

2000-01-01

This study examined the potential for inter-specific differences in root aeration to determine wetland plant distribution in nature. We compared aeration in species that differ in the type of sediment and depth of water they colonize. Differences in root anatomy, structure and physiology were applied to aeration models that predicted the maximum possible aerobic lengths and development of anoxic zones in primary adventitious roots. Differences in anatomy and metabolism that provided higher axial fluxes of oxygen allowed deeper root growth in species that favour more reducing sediments and deeper water. Modelling identified factors that affected growth in anoxic soils through their effects on aeration. These included lateral root formation, which occurred at the expense of extension of the primary root because of the additional respiratory demand they imposed, reducing oxygen fluxes to the tip and stele, and the development of stelar anoxia. However, changes in sediment oxygen demand had little detectable effect on aeration in the primary roots due to their low wall permeability and high surface impedance, but appeared to reduce internal oxygen availability by accelerating loss from laterals. The development of pressurized convective gas flow in shoots and rhizomes was also found to be important in assisting root aeration, as it maintained higher basal oxygen concentrations at the rhizome-root junctions in species growing into deep water. (C) 2000 Annals of Botany Company.

7 CFR 201.55a - Moisture and aeration of substratum.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 3 2013-01-01 2013-01-01 false Moisture and aeration of substratum. 201.55a Section... ACT FEDERAL SEED ACT REGULATIONS Germination Tests in the Administration of the Act § 201.55a Moisture and aeration of substratum. (a) The substratum must be moist enough to supply the needed moisture to...

7 CFR 201.55a - Moisture and aeration of substratum.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 3 2014-01-01 2014-01-01 false Moisture and aeration of substratum. 201.55a Section... ACT FEDERAL SEED ACT REGULATIONS Germination Tests in the Administration of the Act § 201.55a Moisture and aeration of substratum. (a) The substratum must be moist enough to supply the needed moisture to...

7 CFR 201.55a - Moisture and aeration of substratum.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 3 2012-01-01 2012-01-01 false Moisture and aeration of substratum. 201.55a Section... ACT FEDERAL SEED ACT REGULATIONS Germination Tests in the Administration of the Act § 201.55a Moisture and aeration of substratum. (a) The substratum must be moist enough to supply the needed moisture to...

Nitrogen pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes.

PubMed

Brandstätter, Christian; Laner, David; Fellner, Johann

2015-09-01

Nitrogen emissions from municipal solid waste (MSW) landfills occur primarily via leachate, where they pose a long-term pollution problem in the form of ammonium. In-situ aeration was proposed as a remediation measure to mitigate nitrogenous landfill emissions, turning the anaerobic environment to anoxic and subsequently aerobic. As in-depth studies of the nitrogen cycle during landfill aeration had been largely missing, it was the aim of this work to establish a detailed nitrogen balance for aerobic and anaerobic degradation of landfilled MSW based on lab-scale experiments, and also investigating the effect of different water regimes on nitrogen transformation during aeration. Six landfill simulation reactors were operated in duplicate under different conditions: aerated wet (with water addition and recirculation), aerated dry (without water addition) and anaerobic (wet). The results showed that more than 78 % of the initial total nitrogen (TNinit) remained in the solids in all set ups, with the highest nitrogen losses achieved with water addition during aeration. In this case, gaseous nitrogen losses (as N2 due to denitrification) amounted up to 16.6 % of TNinit and around 4 % of TNinit was discharged via leachate. The aerated dry set-up showed lower denitrification rates (2.6-8.8 % of TNinit was released as N2), but was associated with the highest N2O emissions (3.8-3.9 % of TNinit). For the anaerobic treatment the main pathway of nitrogen discharge was the leachate, where NH4 accounted for around 8 % of TNinit. These findings provide the basis for improved management strategies to enhance nitrogen removal during in-situ aeration of old landfills.

Coupling of bio-PRB and enclosed in-well aeration system for remediation of nitrobenzene and aniline in groundwater.

PubMed

Liu, Na; Ding, Feng; Wang, Liu; Liu, Peng; Yu, Xiaolong; Ye, Kang

2016-05-01

A laboratory-scale bio-permeable reactive barrier (bio-PRB) was constructed and combined with enclosed in-well aeration system to treat nitrobenzene (NB) and aniline (AN) in groundwater. Batch-style experiments were first conducted to evaluate the effectiveness of NB and AN degradation, using suspension (free cells) of degrading consortium and immobilized consortium by a mixture of perlite and peat. The NB and AN were completely degraded in <3 days using immobilized consortium, while 3-5 days were required using free cells. The O2 supply efficiency of an enclosed in-well aeration system was assessed in a box filled with perlite and peat. Dissolved O2 (DO) concentrations increased to 8-12 mg L(-1) in 12 h for sampling ports within 12 cm of the aeration well. A diffusion coefficient as 33.5 cm(2) s(-1) was obtained. The DO concentration was >4 mg L(-1) when the aeration system was applied into the bio-PRB system. The NB and AN were effectively removed when the aeration system was functional in the bio-PRB. The removal efficiency decreased when the aeration system malfunctioned for 20 days, thus indicating that DO was an important factor for the degradation of NB and AN. The regain of NB and AN removal after the malfunction indicates the robustness of degradation consortium. No original organics and new formed by-products were observed in the effluent. The results indicate that NB and AN in groundwater can be completely mineralized in a bio-PRB equipped with enclosed in-well aeration system and filled with perlite and peat attached with degrading consortium.

Nitrogen removal in wood chip combined substrate baffled subsurface-flow constructed wetlands: impact of matrix arrangement and intermittent aeration.

PubMed

Li, Huai; Chi, Zifang; Yan, Baixing; Cheng, Long; Li, Jianzheng

2017-02-01

In this study, two lab-scale baffled subsurface-flow constructed wetlands (BSFCWs), including gravel-wood chips-slag and gravel-slag-wood chips, were operated at different intermittent aeration to evaluate the effect of artificial aeration and slow-released carbon source on the treatment efficiency of high-strength nitrogen wastewater. Results indicated that gravel-slag-wood chips extended aerobic/anaerobic alternating environment to gravel and slag zones and maintained anaerobic condition in the subsequent wood chip section. The order of gravel-slag-wood chip was more beneficial to pollutant removal. Sufficient carbon source supply resulted from wood-chip-framework substrate simultaneously obtained high removals of COD (97%), NH 4 + -N (95%), and TN (94%) in BSFCWs at 2 h aeration per day. The results suggest that intermittent aeration combined with wood chips could achieve high nitrogen removal in BSFCWs.

Effect of a large-sized silicone sheet upon recovery of mastoid aeration after mastoidectomy.

PubMed

Kazama, Kyosuke; Takahashi, Haruo; Kaieda, Satoru; Iwanaga, Tetsu; Yamamoto-Fukuda, Tomomi; Yoshida, Haruo; Kumagami, Hidetaka; Takasaki, Kenji

2008-06-01

To evaluate the effect of our large-sized silicone sheet upon postoperative recovery of mastoid aeration in ears after surgery including mastoidectomy and soft-wall reconstruction (SWR). Retrospective chart review in a tertiary care center. Recovery of mastoid aeration was assessed by CT 4 to 12 months after surgery on 72 ears (69 patients), in which the silicone sheet covering from the eustachian tube (ET) to the mastoid was placed after SWR procedure with mastoidectomy were done for their chronic otitis media. Results were compared with those with a small silicone sheet. Recovery of mastoid aeration was significantly better in the large-silicone-sheet group than in the small-silicone-sheet group (chi(2) value = 11.7146, P = 0.0006). This preliminary study suggested that our large-sized silicone sheet may be effective for postoperative recovery of mastoid aeration even in ears operated with SWR procedure.

Improving microalgal growth with small bubbles in a raceway pond with swing gas aerators.

PubMed

Yang, Zongbo; Cheng, Jun; Liu, Jianzhong; Zhou, Junhu; Cen, Kefa

2016-09-01

A novel swing gas aerator was developed to generate small bubbles for improving the mass transfer coefficient and microalgal growth rate in a raceway pond. A high-speed photography system (HSP) was used to measure the bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure the mass transfer coefficient and mixing time. Bubble generation time and diameter decreased by 21% and 9%, respectively, when rubber gas aerators were swung in the microalgae solution. When water pump power and gas aeration rate increased in a raceway pond with swing gas aerators and oscillating baffles (SGAOB), bubble generation time and diameter decreased but solution velocity and mass transfer coefficient increased. The mass transfer coefficient increased by 25% and the solution velocity increased by 11% when SGAOB was used, and the microalgal biomass yield increased by 18%. Copyright © 2016 Elsevier Ltd. All rights reserved.

A novel methodology to quantify nitrous oxide emissions from full-scale wastewater treatment systems with surface aerators.

PubMed

Ye, Liu; Ni, Bing-Jie; Law, Yingyu; Byers, Craig; Yuan, Zhiguo

2014-01-01

The quantification of nitrous oxide (N2O) emissions from open-surface wastewater treatment systems with surface aerators is difficult as emissions from the surface aerator zone cannot be easily captured by floating hoods. In this study, we propose and demonstrate a novel methodology to estimate N2O emissions from such systems through determination of the N2O transfer coefficient (kLa) induced by surface aerators based on oxygen balance for the entire system. The methodology is demonstrated through its application to a full-scale open oxidation ditch wastewater treatment plant with surface aerators. The estimated kLa profile based on a month-long measurement campaign for oxygen balance, intensive monitoring of dissolved N2O profiles along the oxidation ditch over a period of four days, together with mathematical modelling, enabled to determine the N2O emission factor from this treatment plant (0.52 ± 0.16%). Majority of the N2O emission was found to occur in the surface aerator zone, which would be missed if the gas hood method was applied alone. Copyright © 2013 Elsevier Ltd. All rights reserved.

Legionella and non-Legionella bacteria in a biological treatment plant.

PubMed

Fykse, Else Marie; Aarskaug, Tone; Thrane, Ingjerd; Blatny, Janet Martha

2013-02-01

Legionella pneumophila were previously identified in the aeration ponds (up to 10(10) CFU/L) of a biological wastewater treatment plant at Borregaard Ind. Ltd., Sarpsborg, Norway, and in air samples (up to 3300 CFU/m(3)) collected above the aeration ponds. After 3 outbreaks of Legionnaires' disease reported in this area in 2005 and 2008, the aeration ponds of the plant were shut down by the Norwegian authorities in September 2008. The aim of the present work was to analyze the Legionella and non-Legionella bacterial communities in the aeration ponds before and during the shutdown process and to identify potential human pathogens. The non-Legionella bacterial community was investigated in selected samples during the shutdown process by 16S rDNA sequencing of clone libraries (400 clones) and growth analysis. The concentration of L. pneumophila and Pseudomonas spp. DNA were monitored by quantitative PCR. Results showed a decrease in the concentration of L. pneumophila and Pseudomonas spp. during the shutdown. This was accompanied by a significant change in the composition of the bacterial community in the aeration ponds. This study demonstrated that several advanced analytical methods are necessary to characterize the bacterial population in complex environments, such as the industrial aeration ponds.

Maximization of beta-galactosidase production: a simultaneous investigation of agitation and aeration effects.

PubMed

Alves, Fernanda Germano; Filho, Francisco Maugeri; de Medeiros Burkert, Janaína Fernandes; Kalil, Susana Juliano

2010-03-01

In this work, the agitation and aeration effects in the maximization of the beta-galactosidase production from Kluyveromyces marxianus CCT 7082 were investigated simultaneously, in relation to the volumetric enzyme activity and the productivity, as well as the analysis of the lactose consumption and production of glucose, and galactose of this process. Agitation and aeration effects were studied in a 2 L batch stirred reactor. A central composite design (2(2) trials plus three central points) was carried out. Agitation speed varied from 200 to 500 rpm and aeration rate from 0.5 to 1.5 vvm. It has been shown in this study that the volumetric enzyme production was strongly influenced by mixing conditions, while aeration was shown to be less significant. Linear models for activity and productivity due to agitation and aeration were obtained. The favorable condition was 500 rpm and 1.5 vvm, which lead to the best production of 17 U mL(-1) for enzymatic activity, 1.2 U mL(-1) h(-1) for productivity in 14 h of process, a cellular concentration of 11 mg mL(-1), and a 167.2 h(-1) volumetric oxygen transfer coefficient.

Comparison between lab- and full-scale applications of in situ aeration of an old landfill and assessment of long-term emission development after completion.

PubMed

Hrad, Marlies; Gamperling, Oliver; Huber-Humer, Marion

2013-10-01

Sustainable landfilling has become a fundamental objective in many modern waste management concepts. In this context, the in situ aeration of landfills has been recognised for its potential to convert conventional anaerobic landfills into biological stabilised state, whereby both current and potential (long-term) emissions of the landfilled waste are mitigated. In recent years, different in situ aeration concepts have been successfully applied in Europe, North America and Asia, all pursuing different objectives and strategies. In Austria, the first full-scale application of in situ landfill aeration by means of low pressure air injection and simultaneous off-gas collection and treatment was implemented on an old, small municipal solid waste (MSW) landfill (2.6ha) in autumn 2007. Complementary laboratory investigations were conducted with waste samples taken from the landfill site in order to provide more information on the transferability of the results from lab- to full-scale aeration measures. In addition, long-term emission development of the stabilised waste after aeration completion was assessed in an ongoing laboratory experiment. Although the initial waste material was described as mostly stable in terms of the biological parameters gas generation potential over 21days (GP21) and respiration activity over 4days (RA4), the lab-scale experiments indicated that aeration, which led to a significant improvement of leachate quality, was accompanied by further measurable changes in the solid waste material under optimised conditions. Even 75weeks after aeration completion the leachate, as well as gaseous emissions from the stabilised waste material, remained low and stayed below the authorised Austrian discharge limits. However, the application of in situ aeration at the investigated landfill is a factor 10 behind the lab-based predictions after 3years of operation, mainly due to technical limitations in the full-scale operation (e.g. high air flow resistivity due to high water content of waste and temporarily high water levels within the landfill; limited efficiency of the aeration wells). In addition, material preparation (e.g. sieving, sorting and homogenisation) prior to the emplacement in Landfill Simulation Reactors (LSRs) must be considered when transferring results from lab- to full-scale application. Copyright © 2013 Elsevier Ltd. All rights reserved.

Design of top covers supporting aerobic in situ stabilization of old landfills - An experimental simulation in lysimeters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hrad, Marlies; Huber-Humer, Marion, E-mail: marion.huber-humer@boku.ac.at; Wimmer, Bernhard

2012-12-15

Highlights: Black-Right-Pointing-Pointer Tested engineered covers as surrogate to gas extraction during and after in situ aeration. Black-Right-Pointing-Pointer Examined how covers influence gas emissions, water balance and leachate generation. Black-Right-Pointing-Pointer Investigated effect of top covers on air-distribution in waste mass during aeration. Black-Right-Pointing-Pointer We suggest criteria and cover design to meet the demands during and after aeration. Black-Right-Pointing-Pointer Such cover systems may offer greenhouse gas emission reduction also after active aeration. - Abstract: Landfill aeration by means of low pressure air injection is a promising tool to reduce long term emissions from organic waste fractions through accelerated biological stabilization. Top coversmore » that enhance methane oxidation could provide a simple and economic way to mitigate residual greenhouse gas emissions from in situ aerated landfills, and may replace off-gas extraction and treatment, particularly at smaller and older sites. In this respect the installation of a landfill cover system adjusted to the forced-aerated landfill body is of great significance. Investigations into large scale lysimeters (2 Multiplication-Sign 2 Multiplication-Sign 3 m) under field conditions have been carried out using different top covers including compost materials and natural soils as a surrogate to gas extraction during active low pressure aeration. In the present study, the emission behaviour as well as the water balance performance of the lysimeters has been investigated, both prior to and during the first months of in situ aeration. Results reveal that mature sewage sludge compost (SSC) placed in one lysimeter exhibits in principle optimal ambient conditions for methanotrophic bacteria to enhance methane oxidation. Under laboratory conditions the mature compost mitigated CH{sub 4} loadings up to 300 l CH{sub 4}/m{sup 2} d. In addition, the compost material provided high air permeability even at 100% water holding capacity (WHC). In contrast, the more cohesive, mineral soil cover was expected to cause a notably uniform distribution of the injected air within the waste layer. Laboratory results also revealed sufficient air permeability of the soil materials (TS-F and SS-Z) placed in lysimeter C. However, at higher compaction density SS-Z became impermeable at 100% WHC. Methane emissions from the reference lysimeter with the smaller substrate cover (12-52 g CH{sub 4}/m{sup 2} d) were significantly higher than fluxes from the other lysimeters (0-19 g CH{sub 4}/m{sup 2} d) during in situ aeration. Regarding water balance, lysimeters covered with compost and compost-sand mixture, showed the lowest leachate rate (18-26% of the precipitation) due to the high water holding capacity and more favourable plant growth conditions compared to the lysimeters with mineral, more cohesive, soil covers (27-45% of the precipitation). On the basis of these results, the authors suggest a layered top cover system using both compost material as well as mineral soil in order to support active low-pressure aeration. Conventional soil materials with lower permeability may be used on top of the landfill body for a more uniform aeration of the waste due to an increased resistance to vertical gas flow. A compost cover may be built on top of the soil cover underlain by a gas distribution layer to improve methane oxidation rates and minimise water infiltration. By planting vegetation with a high transpiration rate, the leachate amount emanating from the landfill could be further minimised. The suggested design may be particularly suitable in combination with intermittent in situ aeration, in the later stage of an aeration measure, or at very small sites and shallow deposits. The top cover system could further regulate water infiltration into the landfill and mitigate residual CH{sub 4} emissions, even beyond the time of active aeration.« less

Positive effect of reduced aeration rate on growth and stereospecificity of DL-malic acid consumption by Azospirillum brasilense: improving the shelf life of a liquid inoculant formulation.

PubMed

Carrasco-Espinosa, Karen; García-Cabrera, Ramsés I; Bedoya-López, Andrea; Trujillo-Roldán, Mauricio A; Valdez-Cruz, Norma A

2015-02-10

Azospirillum brasilense has significance as a growth promoter in plants of commercial interest. Two industrial native strains (Start and Calf), used as a part of an inoculant formulation in Mexico during the last 15 years, were incubated in laboratory-scale pneumatic bioreactors at different aeration rates. In both strains, the positive effect of decreased aeration was observed. At the lowest (0.1 vvm, air volume/liquid volume×minute), the highest biomass were obtained for Calf (7.8 × 10(10)CFU/ml), and Start (2.9 × 10(9)CFU/ml). These were higher in one magnitude order compared to cultures carried out at 0.5 vvm, and two compared to those at 1.0 vvm. At lower aeration, both stereoisomeric forms of malic acid were consumed, but at higher aeration, just L-malate was consumed. A reduction in aeration allows an increase of the shelf life and the microorganism saved higher concentrations of polyhydroxybutyrate. The selected fermentation conditions are closely related to those prevalent in large-scale bioreactors and offer the possibility of achieving high biomass titles with high shelf life at a reduced costs, due to the complete use of a carbon source at low aeration of a low cost raw material as DL-malic acid mixture in comparison with the L-malic acid stereoisomer. Copyright © 2015 Elsevier B.V. All rights reserved.

A field study on phytoremediation of dredged sediment contaminated by heavy metals and nutrients: the impacts of sediment aeration.

PubMed

Wu, Juan; Yang, Lihua; Zhong, Fei; Cheng, Shuiping

2014-12-01

Compared to traditional chemical or physical treatments, phytoremediation has proved to be a cost-effective and environmentally sound alternative for remediation of contaminated dredged sediment. A field study was conducted in a sediment disposal site predominantly colonized by Typha angustifolia under different sediment moisture conditions to estimate the phytoremediation effects of dredged sediment. The moisture content was 37.30 % and 48.27 % in aerated and waterlogged sediment, respectively. Total nitrogen (TN) content was higher in the waterlogged sediment than in the aerated sediment. The total Cd contents were lower in aerated sediment, which was mainly resulted from the lower exchangeable fraction of Cd. The bioaccumulation of P, Cu and Pb in T. angustifolia was promoted by waterlogging, and the belowground tissue concentrations and accumulation factors (AFs) of Cu were higher than that of other metals, which can be explained by that Cu is an essential micronutrient for plants. Consistent with many previous studies, T. angustifolia showed higher metal levels in roots than in above-ground tissues at both the sediment conditions. Due to the improved biomass produced in the aerated sediment, the removals of nutrients and the metals by plant harvest were higher from aerated sediment than from waterlogged sediment. It was indicated that maintaining the dredged sediment aerated can avoid release risk and plant uptake of metals, while the opposite management option can promote phytoextraction of these contaminants.

Effect of Post-Infiltration Soil Aeration at Different Growth Stages on Growth and Fruit Quality of Drip-Irrigated Potted Tomato Plants (Solanum lycopersicum)

PubMed Central

Li, Yuan; Jia, Zongxia; Niu, Wenquan; Wang, Jingwei; Zhang, Mingzhi

2015-01-01

Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum) at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27–33, 34–57, 58–85, 86–99, and 27–99 days after sowing), on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34–57 DAS) and enlargement (58–85 DAS) growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content), taste (titratable acidity), and market quality (shape and firmness) of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment. PMID:26630675

Comparative study on the reactivity of Fe/Cu bimetallic particles and zero valent iron (ZVI) under different conditions of N2, air or without aeration.

PubMed

Xiong, Zhaokun; Lai, Bo; Yang, Ping; Zhou, Yuexi; Wang, Juling; Fang, Shuping

2015-10-30

In order to further compare the degradation capacity of Fe(0) and Fe/Cu bimetallic system under different aeration conditions, the mineralization of PNP under different aeration conditions has been investigated thoroughly. The results show that the removal of PNP by Fe(0) or Fe/Cu system followed the pseudo-first-order reaction kinetics. Under the optimal conditions, the COD removal efficiencies obtained through Fe(0) or Fe/Cu system under different aeration conditions followed the trend that Fe/Cu (air)>Fe/Cu (N2: 0-30 min, air: 30-120 min)>control-Fe (air)>Fe/Cu (without aeration)>Fe/Cu (N2)>control-Fe (N2). It revealed that dissolved oxygen (DO) could improve the mineralization of PNP, and Cu could enhance the reactivity of Fe(0). In addition, the degradation of PNP was further analyzed by using UV-vis, FTIR and GC/MS, and the results suggest that Fe/Cu bimetallic system with air aeration could completely break the benzene ring and NO2 structure of PNP and could generate the nontoxic and biodegradable intermediate products. Meanwhile, most of these intermediate products were further mineralized into CO2 and H2O, which brought about a high COD removal efficiency (83.8%). Therefore, Fe/Cu bimetallic system with air aeration would be a promising process for toxic refractory industry wastewater. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Post-Infiltration Soil Aeration at Different Growth Stages on Growth and Fruit Quality of Drip-Irrigated Potted Tomato Plants (Solanum lycopersicum).

PubMed

Li, Yuan; Jia, Zongxia; Niu, Wenquan; Wang, Jingwei; Zhang, Mingzhi

2015-01-01

Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum) at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27-33, 34-57, 58-85, 86-99, and 27-99 days after sowing), on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34-57 DAS) and enlargement (58-85 DAS) growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content), taste (titratable acidity), and market quality (shape and firmness) of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment.

Efficient removal of perfluorooctane sulfonate from aqueous film-forming foam solution by aeration-foam collection.

PubMed

Meng, Pingping; Deng, Shubo; Maimaiti, Ayiguli; Wang, Bin; Huang, Jun; Wang, Yujue; Cousins, Ian T; Yu, Gang

2018-07-01

Aqueous film-forming foams (AFFFs) used in fire-fighting are one of the main contamination sources of perfluorooctane sulfonate (PFOS) to the subterranean environment, requiring high costs for remediation. In this study, a method that combined aeration and foam collection was presented to remove PFOS from a commercially available AFFF solution. The method utilized the strong surfactant properties of PFOS that cause it to be highly enriched at air-water interfaces. With an aeration flow rate of 75 mL/min, PFOS removal percent reached 96% after 2 h, and the PFOS concentration in the collected foam was up to 6.5 mmol/L, beneficial for PFOS recovery and reuse. Increasing the aeration flow rate, ionic strength and concentration of co-existing surfactant, as well as decreasing the initial PFOS concentration, increased the removal percents of PFOS by increasing the foam volume, but reduced the enrichment of PFOS in the foams. With the assistance of a co-existing hydrocarbon surfactant, PFOS removal percent was above 99.9% after aeration-foam collection for 2 h and the enrichment factor exceeded 8400. Aeration-foam collection was less effective for short-chain perfluoroalkyl substances due to their relatively lower surface activity. Aeration-foam collection was found to be effective for the removal of high concentrations of PFOS from AFFF-contaminated wastewater, and the concentrated PFOS in the collected foam can be reused. Copyright © 2018 Elsevier Ltd. All rights reserved.

Utilizing whey protein isolate and polysaccharide complexes to stabilize aerated dairy gels.

PubMed

O'Chiu, Emily; Vardhanabhuti, Bongkosh

2017-05-01

Heated soluble complexes of whey protein isolate (WPI) with polysaccharides may be used to modify the properties of aerated dairy gels, which could be formulated into novel-textured high-protein desserts. The objective of this study was to determine the effect of polysaccharide charge density and concentration within a WPI-polysaccharide complex on the physical properties of aerated gels. Three polysaccharides having different degrees of charge density were chosen: low-methoxyl pectin, high-methoxyl type D pectin, and guar gum. Heated complexes were prepared by heating the mixed dispersions (8% protein, 0 to 1% polysaccharide) at pH 7. To form aerated gels, 2% glucono-δ-lactone was added to the dispersions of skim milk powder and heated complex and foam was generated by whipping with a handheld frother. The foam set into a gel as the glucono-δ-lactone acidified to a final pH of 4.5. The aerated gels were evaluated for overrun, drainage, gel strength, and viscoelastic properties. Without heated complexes, stable aerated gels could not be formed. Overrun of aerated gel decreased (up to 73%) as polysaccharide concentration increased from 0.105 to 0.315% due to increased viscosity, which limited air incorporation. A negative relationship was found between percent drainage and dispersion viscosity. However, plotting of drainage against dispersion viscosity separated by polysaccharide type revealed that drainage decreased most in samples with high-charge-density, low-methoxyl pectin followed by those with low-charge-density, high-methoxyl type D pectin. Aerated gels with guar gum (no charge) did not show improvement to stability. Rheological results showed no significant difference in gelation time among samples; therefore, stronger interactions between WPI and high-charge-density polysaccharide were likely responsible for increased stability. Stable dairy aerated gels can be created from WPI-polysaccharide complexes. High-charge-density polysaccharides, at concentrations that provide adequate viscosity, are needed to achieve stability while also maintaining dispersion overrun capabilities. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Aeration and drainage pathways of Prussak's space.

PubMed

Palva, T; Northrop, C; Ramsay, H

2001-01-01

the purpose of this study was to document the aeration and drainage pathways of Prussak's space. 55 temporal bones with an age range from neonate to 11 years of age were serially sectioned to 20 microns, every 10th section was saved and stained by Hematoxylin eosin. Each consecutive section was studied as to the connections of Prussak's space to adjacent compartments and measurements of the dimensions were made for both Prussak's space and its aeration pathways. the classic aeration pathway via the posterior pouch, as described by Prussak in 1867, was found in 34 ears (62%). In 19 (36%), aeration occurred superior to the posterior pouch in the region of the lower lateral attic and the upper mesotympanum. In these ears the posterior pouch had formed, but its superior limit ended blindly in the tympanic membrane. In two temporal bones the aeration pathway was from the anterior pouch and in these cases also a blind posterior pouch had developed. In one temporal bone an auxiliary pathway in addition to the route via the posterior pouch was through the roof (the lateral malleal ligamental fold) of Prussak's space to the overlying lateral malleal space. The height of the posterior pouch varied with a range from 0.5 to 2.4 mm, and the greatest width, which was towards the posterior tympanic spine, varied from 1.6 to 3.2 mm. The superiorly blind posterior pouch was shorter, ranging from 0.4 to 1.2 mm in height. The most frequent route of the chorda tympani nerve was running from 0.5 to 1 mm medial to the posterior malleal ligament in the anterior half of the pouch, joining it posteriorly, or it was connected to it by a short fold, 37 ears (67%). In 18 cases (33%) the chorda was surrounded by its own fold, thus entirely separate from the posterior malleal ligamental fold during its entire course across the tympanum. we have made a detailed documentation of the aeration and drainage pathways of Prussak's space and the findings concur, with important modifications, with Prussak's original description. There is no evidence for contemporary claims that Prussak's space would be aerated superiorly between the lateral incudal and malleal folds. Prussak's space and its aeration pathway is an unit of its own, entirely separate of the major epitympanic compartments which are aerated via the tympanic isthmus. Due to frequent disease processes in the lower lateral attic and posterior mesotympanum, Prussak's space and its aeration pathway are likely to become blocked. This may lead to obliteration of Prussak's space and to the development of retraction pocket or papillary ingrowth cholesteatoma.

Physio-Microstructural Properties of Aerated Cement Slurry for Lightweight Structures

PubMed Central

Salem, Talal; Hamadna, Sameer; Darsanasiri, A. G. N. D.; Soroushian, Parviz; Balchandra, Anagi; Al-Chaar, Ghassan

2018-01-01

Cementitious composites, including ferrocement and continuous fiber reinforced cement, are increasingly considered for building construction and repair. One alternative in processing of these composites is to infiltrate the reinforcement (continuous fibers or chicken mesh) with a flowable cementitious slurry. The relatively high density of cementitious binders, when compared with polymeric binders, are a setback in efforts to introduce cementitious composites as lower-cost, fire-resistant, and durable alternatives to polymer composites. Aeration of the slurry is an effective means of reducing the density of cementitious composites. This approach, however, compromises the mechanical properties of cementitious binders. An experimental program was undertaken in order to assess the potential for production of aerated slurry with a desired balance of density, mechanical performance, and barrier qualities. The potential for nondestructive monitoring of strength development in aerated cementitious slurry was also investigated. This research produced aerated slurries with densities as low as 0.9 g/cm3 with viable mechanical and barrier qualities for production of composites. The microstructure of these composites was also investigated. PMID:29649163

Composting on Mars or the Moon: I. Comparative evaluation of process design alternatives

NASA Technical Reports Server (NTRS)

Finstein, M. S.; Strom, P. F.; Hogan, J. A.; Cowan, R. M.; Janes, H. W. (Principal Investigator)

1999-01-01

As a candidate technology for treating solid wastes and recovering resources in bioregenerative Advanced Life Support, composting potentially offers such advantages as compactness, low mass, near ambient reactor temperatures and pressures, reliability, flexibility, simplicity, and forgiveness of operational error or neglect. Importantly, the interactions among the physical, chemical, and biological factors that govern composting system behavior are well understood. This article comparatively evaluates five Generic Systems that describe the basic alternatives to composting facility design and control. These are: 1) passive aeration; 2) passive aeration abetted by mechanical agitation; 3) forced aeration--O2 feedback control; 4) forced aeration--temperature feedback control; 5) forced aeration--integrated O2 and temperature feedback control. Each of the five has a distinctive pattern of behavior and process performance characteristics. Only Systems 4 and 5 are judged to be viable candidates for ALS on alien worlds, though which is better suited in this application is yet to be determined.

Physio-Microstructural Properties of Aerated Cement Slurry for Lightweight Structures.

PubMed

Almalkawi, Areej T; Salem, Talal; Hamadna, Sameer; Darsanasiri, A G N D; Soroushian, Parviz; Balchandra, Anagi; Al-Chaar, Ghassan

2018-04-12

Cementitious composites, including ferrocement and continuous fiber reinforced cement, are increasingly considered for building construction and repair. One alternative in processing of these composites is to infiltrate the reinforcement (continuous fibers or chicken mesh) with a flowable cementitious slurry. The relatively high density of cementitious binders, when compared with polymeric binders, are a setback in efforts to introduce cementitious composites as lower-cost, fire-resistant, and durable alternatives to polymer composites. Aeration of the slurry is an effective means of reducing the density of cementitious composites. This approach, however, compromises the mechanical properties of cementitious binders. An experimental program was undertaken in order to assess the potential for production of aerated slurry with a desired balance of density, mechanical performance, and barrier qualities. The potential for nondestructive monitoring of strength development in aerated cementitious slurry was also investigated. This research produced aerated slurries with densities as low as 0.9 g/cm³ with viable mechanical and barrier qualities for production of composites. The microstructure of these composites was also investigated.

Changes in carbon and nitrogen pool during in-situ aeration of old landfills under varying conditions.

PubMed

Prantl, R; Tesar, M; Huber-Humer, M; Lechner, P

2006-01-01

Emissions from old landfills via leachate and the gas phase are influenced by state and stability of the organic matter in the solid waste and by environmental conditions within the landfill. Remediation of landfills by means of in-situ aeration is one possibility to reduce these emissions. By establishing aerobic conditions, biological processes in the landfill are accelerated. To investigate the effects of this remediation technology, lab-scale experiments with column tests have been carried out. The main goal of the present work is to characterize the changes of the carbon and nitrogen compounds in the aerated solid waste, the leachate and the gas phase under varying conditions. The results demonstrate a clear reduction of emissions and a stabilization of the organic matter. Furthermore, it is shown that both the intensity of aeration and the amount of water affect biological processes to a certain extent. Even when columns were operated under anaerobic conditions after a long running period of aeration, the emissions remained low.

Epstein-Plesset theory based measurements of concentration of nitrogen gases dissolved in aerated water

NASA Astrophysics Data System (ADS)

Sasaki, Masashi; Yamashita, Tatsuya; Ando, Keita

2016-11-01

Microbubble aeration is used to dissolved gases into water and is an important technique in agriculture and industry. We can measure concentration of dissolved oxygen (DO) in aerated water by commercial DO meters. However, there do not exist commercially available techniques to measure concentration to dissolved nitrogen (DN). In the present study, we propose the method to measure DN in aerated water with the aid of Epstein-Plesset-type analysis. Gas-supersaturated tap water is produced by applying aeration with micro-sized air bubbles and is then stored in a glass container open to the atmosphere. Diffusion-driven growth of bubbles nucleated at the container surface is recorded with a video camera. The bubble growth rate is compare to the extended Epstein-Plesset theory that models mass transfer of both DO and DN into the surface-attached bubbles base on the diffusion equation. Given the DO measurements, we can obtain the DN level by fitting in the comparison.

Effect of limited aeration on the anaerobic treatment of evaporator condensate from a sulfite pulp mill.

PubMed

Zhou, Weili; Imai, Tsuyoshi; Ukita, Masao; Li, Fusheng; Yuasa, Akira

2007-01-01

Serious inhibition was found in the regular up-flow anaerobic sludge blanket (UASB) reactor in treating the evaporator condensate from a sulfite pulp mill, which contained high strength sulfur compounds. After applying the direct limited aeration in the UASB, the inhibition was alleviated gradually and the activity of the microorganisms was recovered. The COD removal rate increased from 40% to 80% at the organic loading rate of 8kgCODm(-3)d(-1) and a hydraulic retention time of 12h. Limited aeration caused no oxygen inhibition to the anaerobic microorganisms but instigated sulfide oxidization and H(2)S removal, which was beneficial to the methanogens. The experiment confirmed the feasibility of applying limited aeration in the anaerobic reactor to alleviate the sulfide inhibition. It also proved that the anaerobic system was actually aerotolerant. SEM observation showed that the predominant microorganisms partly changed from rod-shaped methanogens to cocci after the UASB reactor was aerated.

How effective is aeration with vortex flow regulators? Pilot scale experiments

NASA Astrophysics Data System (ADS)

Wójtowicz, Patryk; Szlachta, Małgorzata

2017-11-01

Vortex flow regulators (VFR) are used in urban drainage systems as a replacement for traditional flow throttling devices. Vortex regulators are not only very efficient energy dissipators but also atomizers which are beneficial for sewer aeration. A deficit of dissolved oxygen can be a problem in both natural waters and sewerage. Hydrodynamic flow regulators can boost oxygen concentration preventing putrefaction and improving treatment of stormwater and wastewater. We were first to investigate the aeration efficiency of semi-commercial scale cylindrical vortex flow regulators to determine the potential of their application in environmental engineering and to propose modification to enhance the aeration capacity of basic designs. Different device geometries and arrangements of active outlets for both single and double discharge vortex regulators were tested in a recirculating system. In this study, we present a concise review of the current state of our extensive research on the aeration efficiency of vortex flow regulators and their application in sewerage systems.

Cost-performance analysis of nutrient removal in a full-scale oxidation ditch process based on kinetic modeling.

PubMed

Li, Zheng; Qi, Rong; Wang, Bo; Zou, Zhe; Wei, Guohong; Yang, Min

2013-01-01

A full-scale oxidation ditch process for treating sewage was simulated with the ASM2d model and optimized for minimal cost with acceptable performance in terms of ammonium and phosphorus removal. A unified index was introduced by integrating operational costs (aeration energy and sludge production) with effluent violations for performance evaluation. Scenario analysis showed that, in comparison with the baseline (all of the 9 aerators activated), the strategy of activating 5 aerators could save aeration energy significantly with an ammonium violation below 10%. Sludge discharge scenario analysis showed that a sludge discharge flow of 250-300 m3/day (solid retention time (SRT), 13-15 days) was appropriate for the enhancement of phosphorus removal without excessive sludge production. The proposed optimal control strategy was: activating 5 rotating disks operated with a mode of "111100100" ("1" represents activation and "0" represents inactivation) for aeration and sludge discharge flow of 200 m3/day (SRT, 19 days). Compared with the baseline, this strategy could achieve ammonium violation below 10% and TP violation below 30% with substantial reduction of aeration energy cost (46%) and minimal increment of sludge production (< 2%). This study provides a useful approach for the optimization of process operation and control.

Impact of aeration disturbances on endogenous phosphorus fractions and their algae growth potential from malodorous river sediment.

PubMed

Zhu, Jin; He, Yan; Wang, Jianhua; Qiao, Zhaochao; Wang, Yi; Li, Zhihong; Huang, Minsheng

2017-03-01

The present work assessed the impact of aeration disturbances on sediment-bound phosphorus fractions and their algae growth potential from a typical malodorous river. Phosphorus was sequentially extracted by a modified version of Hedley fractionation method. It was found that the mean contents of TP was 1476.1 ± 60.3 mg/kg, consisting mainly of dilute HCl-extractable P (52.6%) and NaOH-P (19.2%). The algae growth potential tests demonstrated that algae growth had varied P-level requirements for different P speciation and NaOH-P promoted algae growth remarkably and its promoting effect was positively related to its concentration. Additionally, intermittent overlying water aeration modes were recommended, and run 1 (7.0 mg/L, 12 h) was deemed as the optimized aerated mode in terms of its relatively low ecological risk and high P retention. It was noted that NaOH-P was most affected by aeration disturbance and exhibited marked increase with the elevated dissolved oxygen (DO) level whether for intermittent overlying water or sediment aeration. This research helps to gain improved understanding of the ecological risk on sediment P, and NaOH-P is recognized as one ecologically important P fraction in the sediments considering its relatively high proportion and bioavailability.

A triple fouling layers perspective on evaluation of membrane fouling under different scenarios of membrane bioreactor operation

PubMed Central

2014-01-01

One of the main factors affecting membrane fouling in MBRs is operational conditions. In this study the influence of aeration rate, filtration mode, and SRT on hollow fiber membrane fouling was investigated using a triple fouling layers perspective. The sludge microbial population distribution was also determined by PCR method. Through various applied operational scenarios the optimal conditions were: aeration rate of 15 LPM; relaxation mode with 40s duration and 8 min. interval; and SRT of 30 days. The similarity between SMP variations in triple fouling layers with its corresponding hydraulic resistance confirmed the effect of SMP on membrane fouling. Among three fouling fractions, the upper (rinsed) layer found to have the most effect on membrane fouling which implies the critical role of aeration, but as for multilateral effects of aeration, the optimal aeration rate should be determined more precisely. Relaxation interval was more effective than its duration for fouling control. SRT variations in addition to influencing the amount of SMP, also affect on the structure of these material. At longer SRTs (20, 30 days) a greater percentage of SMP could penetrate into the membrane pores and for shorter SRTs they accumulate more on membrane surface. Results showed that there is a very good correlation between total hydraulic resistance (Log R) and protein to carbohydrate ratio at the rinsed layer (P1/C1). Considering significant effects of aeration and SRT conditions on this ratio (according to data), it is very determinative to apply the optimal aeration and SRT conditions. PMID:25002969

Characterization of the external and internal flow structure of an aerated-liquid injector using X-ray radiography and fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peltier, Scott J.; Lin, Kuo-Cheng; Carter, Campbell D.

In the present study, the internal flowfield of aerated-liquid fuel injectors is examined through x-ray radiography and x-ray fluorescence. An inside-out injector, consisting of a perforated aerating tube within an annular liquid stream, sprays into a quiescent environment at a fixed mass flow rate of water and nitrogen gas. The liquid is doped with bromine (in the form of NaBr) to create an x-ray fluorescence signal. This allows for reasonable absorption and fluorescence signals, and one or both diagnostics can be used to track the liquid distribution. The injector housing is fabricated from beryllium (Be), which allows the internal flowfieldmore » to be examined (as Be has relatively low x-ray attenuation coefficient). Two injector geometries are compared, illustrating the effects of aerating orifice size and location on the flow evolution. Time-averaged equivalent pathlength (EPL) and line-of-sight averaged density ρ(y) reveal the formation of the two-phase mixture, showing that the liquid film thickness along the injector walls is a function of the aerating tube geometry, though only upstream of the nozzle. These differences in gas and liquid distribution (between injectors with different aerating tube designs) are suppressed as the mixture traverses the nozzle contraction. The averaged liquid velocity (computed from the density and liquid mass flow rate) reveal a similar trend. This suggests that at least for the current configurations, the plume width, liquid mass distribution, and averaged liquid velocity for the time-averaged external spray are insensitive to the aerating tube geometry.« less

Simultaneous nitrification, denitrification, and phosphorus removal in single-tank low-dissolved-oxygen systems under cyclic aeration.

PubMed

Ju, Lu-Kwang; Huang, Lin; Trivedi, Hiren

2007-08-01

Simultaneous nitrification and denitrification (SND or SNdN) may occur at low dissolved oxygen concentrations. In this study, bench-scale (approximately 6 L) bioreactors treating a continuous feed of synthetic wastewater were used to evaluate the effects of solids retention time and low dissolved oxygen concentration, under cyclic aeration, on the removal of organics, nitrogen, and phosphorus. The cyclic aeration was carried out with repeated cycles of 1 hour at a higher dissolved oxygen concentration (HDO) and 30 minutes at a lower (or zero) dissolved oxygen concentration (LDO). Compared with aeration at constant dissolved oxygen concentrations, the cyclic aeration, when operated with proper combinations of HDO and LDO, produced better-settling sludge and more complete nitrogen and phosphorus removal. For nitrogen removal, the advantage resulted from the more readily available nitrate and nitrite (generated by nitrification during the HDO period) for denitrification (during the LDO period). For phosphorus removal, the advantage of cyclic aeration came from the development of a higher population of polyphosphate-accumulating organisms, as indicated by the higher phosphorus contents in the sludge solids of the cyclically aerated systems. Nitrite shunt was also observed to occur in the LDO systems. Higher ratios of nitrite to nitrate were found in the systems of lower HDO (and, to less dependency, higher LDO), suggesting that the nitrite shunt took place mainly because of the disrupted nitrification at lower HDO. The study results indicated that the HDO used should be kept reasonably high (approximately 0.8 mg/L) or the HDO period prolonged, to promote adequate nitrification, and the LDO kept low (< or =0.2 mg/L), to achieve more complete denitrification and higher phosphorus removal. The above findings in the laboratory systems find strong support from the results obtained in full-scale plant implementation. Two plant case studies using the cyclic low-dissolved-oxygen aeration for creating and maintaining SND are also presented.

A comparative study of leachate quality and biogas generation in simulated anaerobic and hybrid bioreactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Qiyong; Tian, Ying; Wang, Shen

2015-07-15

Highlights: • Temporary aeration shortened the initial acid inhibition phase for methanogens. • COD decreased faster in the hybrid bioreactor than that in the anaerobic control. • Methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. • MSW settlement increased with increasing the frequency of intermittent aeration. - Abstract: Research has been conducted to compare leachate characterization and biogas generation in simulated anaerobic and hybrid bioreactor landfills with typical Chinese municipal solid waste (MSW). Three laboratory-scale reactors, an anaerobic (A1) and two hybrid bioreactors (C1 and C2), were constructed and operated for about 10 months. Themore » hybrid bioreactors were operated in an aerobic–anaerobic mode with different aeration frequencies by providing air into the upper layer of waste. Results showed that the temporary aeration into the upper layer aided methane generation by shortening the initial acidogenic phase because of volatile fatty acids (VFAs) reduction and pH increase. Chemical oxygen demand (COD) decreased faster in the hybrid bioreactors, but the concentrations of ammonia–nitrogen in the hybrid bioreactors were greater than those in the anaerobic control. Methanogenic conditions were established within 75 d and 60 d in C1 and C2, respectively. However, high aeration frequency led to the consumption of organic matters by aerobic degradation and resulted in reducing accumulative methane volume. The temporary aeration enhanced waste settlement and the settlement increased with increasing the frequency of aeration. Methane production was inhibited in the anaerobic control; however, the total methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. As for MSW with high content of food waste, leachate recirculation right after aeration stopped was not recommended due to VFA inhibition for methanogens.« less

Automatic quantitative computed tomography segmentation and analysis of aerated lung volumes in acute respiratory distress syndrome-A comparative diagnostic study.

PubMed

Klapsing, Philipp; Herrmann, Peter; Quintel, Michael; Moerer, Onnen

2017-12-01

Quantitative lung computed tomographic (CT) analysis yields objective data regarding lung aeration but is currently not used in clinical routine primarily because of the labor-intensive process of manual CT segmentation. Automatic lung segmentation could help to shorten processing times significantly. In this study, we assessed bias and precision of lung CT analysis using automatic segmentation compared with manual segmentation. In this monocentric clinical study, 10 mechanically ventilated patients with mild to moderate acute respiratory distress syndrome were included who had received lung CT scans at 5- and 45-mbar airway pressure during a prior study. Lung segmentations were performed both automatically using a computerized algorithm and manually. Automatic segmentation yielded similar lung volumes compared with manual segmentation with clinically minor differences both at 5 and 45 mbar. At 5 mbar, results were as follows: overdistended lung 49.58mL (manual, SD 77.37mL) and 50.41mL (automatic, SD 77.3mL), P=.028; normally aerated lung 2142.17mL (manual, SD 1131.48mL) and 2156.68mL (automatic, SD 1134.53mL), P = .1038; and poorly aerated lung 631.68mL (manual, SD 196.76mL) and 646.32mL (automatic, SD 169.63mL), P = .3794. At 45 mbar, values were as follows: overdistended lung 612.85mL (manual, SD 449.55mL) and 615.49mL (automatic, SD 451.03mL), P=.078; normally aerated lung 3890.12mL (manual, SD 1134.14mL) and 3907.65mL (automatic, SD 1133.62mL), P = .027; and poorly aerated lung 413.35mL (manual, SD 57.66mL) and 469.58mL (automatic, SD 70.14mL), P=.007. Bland-Altman analyses revealed the following mean biases and limits of agreement at 5 mbar for automatic vs manual segmentation: overdistended lung +0.848mL (±2.062mL), normally aerated +14.51mL (±49.71mL), and poorly aerated +14.64mL (±98.16mL). At 45 mbar, results were as follows: overdistended +2.639mL (±8.231mL), normally aerated 17.53mL (±41.41mL), and poorly aerated 56.23mL (±100.67mL). Automatic single CT image and whole lung segmentation were faster than manual segmentation (0.17 vs 125.35seconds [P<.0001] and 10.46 vs 7739.45seconds [P<.0001]). Automatic lung CT segmentation allows fast analysis of aerated lung regions. A reduction of processing times by more than 99% allows the use of quantitative CT at the bedside. Copyright © 2016 Elsevier Inc. All rights reserved.

Polyhydroxyalkanoate synthesis by mixed microbial consortia cultured on fermented dairy manure: Effect of aeration on process rates/yields and the associated microbial ecology.

PubMed

Coats, Erik R; Watson, Benjamin S; Brinkman, Cynthia K

2016-12-01

Polyhydroxyalkanoates (PHAs) are biodegradable polymers that can substitute for petroleum-based plastics in a variety of applications. One avenue to commercial PHA production involves coupling waste-based synthesis with the use of mixed microbial consortia (MMC). In this regard, production requires maximizing the enrichment of a MMC capable of feast-famine PHA synthesis, with the metabolic response induced through imposition of aerobic-dynamic feeding (ADF) conditions. However, the concept of PHA production in complex matrices remains unrefined; process operational improvements are needed, along with an enhanced understanding of the MMC. Research presented herein investigated the effect of aeration on feast-famine PHA synthesis, with four independent aeration state systems studied; MMC were fed volatile fatty acid (VFA)-rich fermented dairy manure. Regardless of the aeration state, all MMC exhibited a feast-famine response based on observed carbon cycling. Moreover, there was no statistical difference in PHA synthesis rates, with q PHA ranging from 0.10 to 0.19 CmmolPHA gVSS -1 min -1 ; VFA uptake rates exhibited similar statistical indifferences. PHA production assessments on the enriched MMC resulted in maximum intracellular concentrations ranging from 22.5 to 90.7% (mgPHA mgVSS -1 ); at maximum concentration, the mean hydroxyvalerate mol content was 73 ± 0.6%. While a typical feast-famine dissolved oxygen (DO) pattern was observed at maximum aeration, less resolution was observed at decreasing aeration rates, suggesting that DO may not be an optimal process monitoring parameter. At lower aeration states, nitrogen cycling patterns, supported by molecular investigations targeting AOBs and NOBs, indicate that NO 2 and NO 3 sustained feast-famine PHA synthesis. Next-generation sequencing analysis of the respective MMC revealed numerous and diverse genera exhibiting the potential to achieve PHA synthesis, suggesting functional redundancy embedded in the diverse MMC. Ultimately, results demonstrate that aeration can be controlled in waste-based ADF systems to sustain PHA production potential, while enriching for a diverse MMC that exhibits potential functional redundancy. Reduced aeration could also enhance cost competitiveness of waste-based PHA production, with potential further benefits associated with nitrogen treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

USSR and Eastern Europe Scientific Abstracts, Biomedical and Behavioral Sciences. Number 70

DTIC Science & Technology

1977-05-04

are quite dependent on type of plant. Figures 5; Table 1; References 4: 1 Russian, 3 Western. USSR UDC 626.843+631.54 AERATING TREATMENT OF THE SOD...perennial grasses, application of mineral fertilizers and the aeration treatment described above) lengthens the productive year of irrigated...pastures, producing a harvest of 6-8*103 feed units/ha. Aerating treatment of the soddy layer is thus a promising method of cultivation of pastures

A combined system of microbial fuel cell and intermittently aerated biological filter for energy self-sufficient wastewater treatment.

PubMed

Dong, Yue; Feng, Yujie; Qu, Youpeng; Du, Yue; Zhou, Xiangtong; Liu, Jia

2015-12-15

Energy self-sufficiency is a highly desirable goal of sustainable wastewater treatment. Herein, a combined system of a microbial fuel cell and an intermittently aerated biological filter (MFC-IABF) was designed and operated in an energy self-sufficient manner. The system was fed with synthetic wastewater (COD = 1000 mg L(-1)) in continuous mode for more than 3 months at room temperature (~25 °C). Voltage output was increased to 5 ± 0.4 V using a capacitor-based circuit. The MFC produced electricity to power the pumping and aeration systems in IABF, concomitantly removing COD. The IABF operating under an intermittent aeration mode (aeration rate 1000 ± 80 mL h(-1)) removed the residual nutrients and improved the water quality at HRT = 7.2 h. This two-stage combined system obtained 93.9% SCOD removal and 91.7% TCOD removal (effluent SCOD = 61 mg L(-1), TCOD = 82.8 mg L(-1)). Energy analysis indicated that the MFC unit produced sufficient energy (0.27 kWh m(-3)) to support the pumping system (0.014 kWh m(-3)) and aeration system (0.22 kWh m(-3)). These results demonstrated that the combined MFC-IABF system could be operated in an energy self-sufficient manner, resulting to high-quality effluent.

Internal aeration of paddy field rice (Oryza sativa) during complete submergence---importance of light and floodwater O2.

PubMed

Winkel, Anders; Colmer, Timothy D; Ismail, Abdelbagi M; Pedersen, Ole

2013-03-01

Flash floods can submerge paddy field rice (Oryza sativa), with adverse effects on internal aeration, sugar status and survival. Here, we investigated the in situ aeration of roots of rice during complete submergence, and elucidated how underwater photosynthesis and floodwater pO(2) influence root aeration in anoxic soil. In the field, root pO(2) was measured using microelectrodes during 2 d of complete submergence. Leaf gas films that formed on the superhydrophobic leaves were left intact, or experimentally removed, to elucidate their effect on internal aeration. In darkness, root pO(2) declined to very low concentrations (0.24 kPa) and was strongly correlated with floodwater pO(2). In light, root pO(2) was high (14 kPa) and primarily a function of the incident light determining the rates of underwater net photosynthesis. Plants with intact leaf gas films maintained higher underwater net photosynthesis relative to plants without gas films when the submerged shoots were in light. During complete submergence, internal aeration of rice in the field relies on underwater photosynthesis during the day and entry of O(2) from the floodwater during the night. Leaf gas films enhance photosynthesis during submergence leading to improved O(2) production and sugar status, and therefore contribute to the submergence tolerance of rice. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Modelling oxygen transfer using dynamic alpha factors.

PubMed

Jiang, Lu-Man; Garrido-Baserba, Manel; Nolasco, Daniel; Al-Omari, Ahmed; DeClippeleir, Haydee; Murthy, Sudhir; Rosso, Diego

2017-11-01

Due to the importance of wastewater aeration in meeting treatment requirements and due to its elevated energy intensity, it is important to describe the real nature of an aeration system to improve design and specification, performance prediction, energy consumption, and process sustainability. Because organic loadings drive aeration efficiency to its lowest value when the oxygen demand (energy) is the highest, the implications of considering their dynamic nature on energy costs are of utmost importance. A dynamic model aimed at identifying conservation opportunities is presented. The model developed describes the correlation between the COD concentration and the α factor in activated sludge. Using the proposed model, the aeration efficiency is calculated as a function of the organic loading (i.e. COD). This results in predictions of oxygen transfer values that are more realistic than the traditional method of assuming constant α values. The model was applied to two water resource recovery facilities, and was calibrated and validated with time-sensitive databases. Our improved aeration model structure increases the quality of prediction of field data through the recognition of the dynamic nature of the alpha factor (α) as a function of the applied oxygen demand. For the cases presented herein, the model prediction of airflow improved by 20-35% when dynamic α is used. The proposed model offers a quantitative tool for the prediction of energy demand and for minimizing aeration design uncertainty. Copyright © 2017 Elsevier Ltd. All rights reserved.

A novel open-type biosensor for the in-situ monitoring of biochemical oxygen demand in an aerobic environment

PubMed Central

Yamashita, Takahiro; Ookawa, Natsuki; Ishida, Mitsuyoshi; Kanamori, Hiroyuki; Sasaki, Harumi; Katayose, Yuichi; Yokoyama, Hiroshi

2016-01-01

Biochemical oxygen demand (BOD) is a widely used index of water-quality assessment. Since bioelectrochemical BOD biosensors require anaerobic conditions for anodic reactions, they are not directly used in aerobic environments such as aeration tanks. Normally, the BOD biosensors are closed-type, where the anode is packed inside a closed chamber to avoid exposure to oxygen. In this study, a novel bioelectrochemical open-type biosensor was designed for in-situ monitoring of BOD during intermittent aeration. The open-type anode, without any protection against exposure to oxygen, was directly inserted into an intermittently aerated tank filled with livestock wastewater. Anodic potential was controlled using a potentiostat. Interestingly, this novel biosensor generated similar levels of current under both aerating and non-aerating conditions, and showed a logarithmic correlation (R2 > 0.9) of current with BOD concentrations up to 250 mg/L. Suspended solids in the wastewater attached to and covered the whole anode, presumably leading to the production of anaerobic conditions inside the covered anode via biological oxygen removal. Exoelectrogenic anaerobes (Geobacter spp.) were detected inside the covered anode using the 16S-rRNA gene. This biosensor will have various practical applications, such as the automatic control of aeration intensity and the in-situ monitoring of natural water environments. PMID:27917947

Aerated drilling cutting transport analysis in geothermal well

NASA Astrophysics Data System (ADS)

Wakhyudin, Aris; Setiawan, Deni; Dwi Marjuan, Oscar

2017-12-01

Aeratad drilling widely used for geothermal drilling especially when drilled into predicted production zone. Aerated drilling give better performance on preventing lost circulation problem, improving rate of penetration, and avoiding drilling fluid invasion to productive zone. While well is drilled, cutting is produced and should be carried to surface by drilling fluid. Hole problem, especially pipe sticking will occur while the cutting is not lifted properly to surface. The problem will effect on drilling schedule; non-productive time finally result more cost to be spent. Geothermal formation has different characteristic comparing oil and gas formation. Geothermal mainly has igneous rock while oil and gas mostly sedimentary rock. In same depth, formation pressure in geothermal well commonly lower than oil and gas well while formation temperature geothermal well is higher. While aerated drilling is applied in geothermal well, Igneous rock density has higher density than sedimentary rock and aerated drilling fluid is lighter than water based mud hence minimum velocity requirement to transport cutting is larger than in oil/gas well drilling. Temperature and pressure also has impact on drilling fluid (aerated) density. High temperature in geothermal well decrease drilling fluid density hence the effect of pressure and temperature also considered. In this paper, Aerated drilling cutting transport performance on geothermal well will be analysed due to different rock and drilling fluid density. Additionally, temperature and pressure effect on drilling fluid density also presented to merge.

Influence of forced air volume on water evaporation during sewage sludge bio-drying.

PubMed

Cai, Lu; Chen, Tong-Bin; Gao, Ding; Zheng, Guo-Di; Liu, Hong-Tao; Pan, Tian-Hao

2013-09-01

Mechanical aeration is critical to sewage sludge bio-drying, and the actual water loss caused by aeration can be better understood from investigations of the relationship between aeration and water evaporation from the sewage sludge bio-drying pile based on in situ measurements. This study was conducted to investigate the effects of forced air volume on the evaporation of water from a sewage sludge bio-drying pile. Dewatered sewage sludge was bio-dried using control technology for bio-drying, during which time the temperature, superficial air velocity and water evaporation were measured and calculated. The results indicated that the peak air velocity and water evaporation occurred in the thermophilic phase and second temperature-increasing phase, with the highest values of 0.063 ± 0.027 m s(-1) and 28.9 kg ton(-1) matrix d(-1), respectively, being observed on day 4. Air velocity above the pile during aeration was 43-100% higher than when there was no aeration, and there was a significantly positive correlation between air volume and water evaporation from day 1 to 15. The order of daily means of water evaporation was thermophilic phase > second temperature-increasing phase > temperature-increasing phase > cooling phase. Forced aeration controlled the pile temperature and improved evaporation, making it the key factor influencing water loss during the process of sewage sludge bio-drying. Copyright © 2013 Elsevier Ltd. All rights reserved.

Impact of fouling on the decline of aeration efficiency under different operational conditions at WRRFs.

PubMed

Garrido-Baserba, Manel; Asvapathanagul, Pitiporn; Park, Hee-Deung; Kim, Taek-Seung; Baquero-Rodriguez, G Andres; Olson, Betty H; Rosso, Diego

2018-10-15

Biofilm formation influences the most energy-demanding process in the waste water treatment cycle. Biofilm growth on the surface of wastewater aeration diffusers in water resource recovery facilities (WRRFs) can increase the energy requirements up to 50% in less than 2 years. The impact of biofilms in aeration diffusers was quantified and assessed for first time using molecular tools (i.e., Energy-dispersive X-ray, Ra and RMS and Pyrosequencing) and state-of-the-art techniques (i.e., EPS quantification, Hydrophobicity and DNA quantification). To provide a better understanding and quantitative connections between biological activity and aeration energy efficiency, two replicates of the most common diffusers were installed and tested in two different operational conditions (higher and lower organic loading rate processes) during 15 months. Different scenarios and conditions provided for first time comprehensive understanding of the major factors contributing to diffuser fouling. The array of analysis suggested that higher loading conditions can promote specialized microbial populations to halve aeration efficiency parameters (i.e., αF) in comparison to lower loading conditions. Biofilms adapted to certain operational conditions can trigger changes in diffuser membrane properties (i.e., biological enhanced roughness and hydrophobicity) and enhance EPS growth rates. Improved understanding of the effects of scaling, biofouling, aging and microbial population shifts on the decrease in aeration efficiency is provided. Copyright © 2018 Elsevier B.V. All rights reserved.

Municipal waste stabilization in a reactor with an integrated active and passive aeration system.

PubMed

Kasinski, Slawomir; Slota, Monika; Markowski, Michal; Kaminska, Anna

2016-04-01

To test whether an integrated passive and active aeration system could be an effective solution for aerobic decomposition of municipal waste in technical conditions, a full-scale composting reactor was designed. The waste was actively aerated for 5d, passively aerated for 35 d, and then actively aerated for 5d, and the entire composting process was monitored. During the 45-day observation period, changes in the fractional, morphological and physico-chemical characteristics of the waste at the top of the reactor differed from those in the center of the reactor. The fractional and morphological analysis made during the entire process of stabilization, showed the total reduction of organic matter measured of 82 wt% and 86 wt% at the respective depths. The reduction of organic matter calculated using the results of Lost of Ignition (LOI) and Total Organic Carbon (TOC) showed, respectively, 40.51-46.62% organic matter loss at the top and 45.33-53.39% in the center of the reactor. At the end of the process, moisture content, LOI and TOC at the top were 3.29%, 6.10% and 4.13% higher, respectively, than in the center. The results showed that application of passive aeration in larger scale simultaneously allows the thermophilic levels to be maintained during municipal solid waste composting process while not inhibiting microbial activity in the reactor. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recirculation or artificial aeration in vertical flow constructed wetlands: a comparative study for treating high load wastewater.

PubMed

Foladori, Paola; Ruaben, Jenny; Ortigara, Angela R C

2013-12-01

Vertical subsurface-flow constructed wetlands at pilot-scale have been applied to treat high hydraulic and organic loads by implementing the following configurations: (1) intermittent recirculation of the treated wastewater from the bottom to the top of the bed, (2) intermittent artificial aeration supplied at the bottom of the bed and (3) the combination of both. These configurations were operated with a saturated bottom layer for a 6h-treatment phase, followed by a free drainage phase prior to a new feeding. COD removal efficiency was 85-90% in all the configurations and removed loads were 54-70 gCOD m(-2)d(-1). The aerated and recirculated wetland resulted in a higher total nitrogen removal (8.6 gN m(-2)d(-1)) due to simultaneous nitrification/denitrification, even in the presence of intermittent aeration (6.8 Nm(3)m(-2)d(-1)). The extra investment needed for implementing aeration/recirculation would be compensated for by a reduction of the surface area per population equivalent, which decreased to 1.5m(2)/PE. Copyright © 2013 Elsevier Ltd. All rights reserved.

Composite wastewater treatment by aerated electrocoagulation and modified peroxi-coagulation processes.

PubMed

Kumar, Abhijeet; Nidheesh, P V; Suresh Kumar, M

2018-08-01

Treatment of composite wastewater generating from the industrial estates is a great challenge. The present study examines the applicability of aerated electrocoagulation and modified peroxi-coagulation processes for removing color and COD from composite wastewater. Iron plates were used as anodes and cathodes in both electrochemical processes and experiments were carried out in a working volume of 2 L. Aeration enhanced the efficiency of electrocoagulation process significantly. More than 50% of COD and 60% of color were removed after 1 h of electrocoagulation process operated at pH 3 and applied voltage of 1 V. Efficiency of the modified peroxi-coagulation process was significantly higher than that of aerated electrocoagulation. COD and color removal efficiencies of the modified peroxi-coagulation process were found as 77.7% and 97%, respectively after 1 h of electrolysis operated at 1 V, solution pH 3 and 50 mM hydrogen peroxide addition. This improved efficiency of modified peroxi-coagulation compared to aerated electrocoagulation is mainly due to the attack of in-situ generated hydroxyl radicals. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of micro-aeration on anaerobic digestion of primary sludge under septic tank conditions.

PubMed

Diak, James; Örmeci, Banu; Kennedy, Kevin J

2013-04-01

Micro-aeration, which refers to the addition of very small amounts of air, is a simple technology that can potentially be incorporated in septic tanks to improve the digestion performance. The purpose of this study was to investigate and compare the effects of micro-aeration on anaerobic digestion of primary sludge under septic tank conditions. 1.6 L batch reactor experiments were carried out in duplicate using raw primary sludge, with 4.1 % total solids, and diluted primary sludge, with 2.1 % total solids. Reactors were operated for 5 weeks at room temperature to simulate septic tank conditions. Micro-aeration rate of 0.00156 vvm effectively solubilised chemical oxygen demand (COD) and improved the subsequent degradation of COD. Micro-aeration also increased the generation of ammonia and soluble proteins, but did not improve the reduction in total and volatile solids, or the reduction in carbohydrates. Experiments using diluted sludge samples showed similar trends as the experiments with raw sludge, which suggest that initial solids concentration did not have a significant effect on the degradation of primary sludge under septic tank conditions.

Application of airlift bioreactor for the cultivation of aerobic oleaginous yeast Rhodotorula glutinis with different aeration rates.

PubMed

Yen, Hong-Wei; Liu, Yi Xian

2014-08-01

The high cost of microbial oils produced from oleaginous microorganisms is the major obstacle to commercial production. In this study, the operation of an airlift bioreactor is examined for the cultivation of oleaginous yeast-Rhodotorula glutinis, due to the low process cost. The results suggest that the use of a high aeration rate could enhance cell growth. The maximum biomass concentration of 25.40 g/L was observed in the batch with a 2.0 vvm aeration rate. In addition, a higher aeration rate of 2.5 vvm could achieve the maximum growth rate of 0.46 g/L h, about twice the 0.22 g/L h obtained in an agitation tank. However, an increase in tank pressure instead of the aeration rate did not enhance cell growth. The operation of airlift bioreactor described in this work has the advantages of simple operation and low energy consumption, thus making it suitable for the accumulation of microbial oils. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Acid mine water aeration and treatment system

DOEpatents

Ackman, Terry E.; Place, John M.

1987-01-01

An in-line system is provided for treating acid mine drainage which basically comprises the combination of a jet pump (or pumps) and a static mixer. The jet pump entrains air into the acid waste water using a Venturi effect so as to provide aeration of the waste water while further aeration is provided by the helical vanes of the static mixer. A neutralizing agent is injected into the suction chamber of the jet pump and the static mixer is formed by plural sections offset by 90 degrees.

Porosimetric, Thermal and Strength Tests of Aerated and Nonaerated Concretes

NASA Astrophysics Data System (ADS)

Strzałkowski, Jarosław; Garbalińska, Halina

2017-10-01

The paper presents the results of porosimetry tests of lightweight concretes, obtained with three research methods. Impact of different porosity structures on the basic thermal and strength properties was also evaluated. Tests were performed, using the pressure gauge method on fresh concrete mixes, as well as using the mercury porosimetry test and optic RapidAir method on specimens prepared from mature composites. The study was conducted on lightweight concretes, based on expanded clay aggregate and fly ash aggregate, in two variants: with non-aerated and aerated cement matrix. In addition, two reference concretes, based on normal aggregate, were prepared, also in two variants of matrix aeration. Changes in thermal conductivity λ and volumetric specific heat cv throughout the first three months of curing of the concretes were examined. Additionally, tests for compressive strength on cubic samples were performed during the first three months of curing. It was found that the pressure gauge method, performed on a fresh mix, gave lowered values of porosity, compared to the other methods. The mercury porosity tests showed high sensitivity in evaluation of pores smaller than 30μm. Unfortunately, this technique is not suitable for analysing pores greater than 300μm. On the other hand, the optical method proves good in evaluation of large pores, greater than 300μm. The paper also presents results of correlation of individual methods of porosity testing. A consolidated graph of the pore structure, derived from both mercury and optical methods, was presented, too. For the all of six tested concretes, differential graphs of porosity, prepared with both methods, show a very broad convergence. The thermal test results indicate usefulness of aeration of the cement matrix of the composites based on lightweight aggregates for the further reduction of the thermal conductivity coefficient λ of the materials. The lowest values of the λ coefficient were obtained for the aerated concretes based of fly ash aggregate. A diminishing influence of aeration on the volumetric heat capacity cv is clearly seen. Simultaneous aeration of the matrix and use of lightweight aggregates brought about also a significant decrease in the average compressive strength fcm of the tested composites.

Culture characteristics of the atmospheric and room temperature plasma-mutated Spirulina platensis mutants in CO2 aeration culture system for biomass production.

PubMed

Tan, Yinyee; Fang, Mingyue; Jin, Lihua; Zhang, Chong; Li, He-Ping; Xing, Xin-Hui

2015-10-01

For biomass production of Spirulina platensis as feedstock of fermentation, the culture characteristics of three typical mutants of 3-A10, 3-B2 and 4-B3 generated by atmospheric and room temperature plasmas (ARTP) mutagenesis were systematically studied by using CO2 aeration culture system and compared with the wild strain. The specific growth rate of wild strain in the pure air aeration culture system exhibited a 76.2% increase compared with static culture, while the specific growth rates of the 3-A10, 3-B2 and 4-B3 in pure air aeration culture system were increased by 114.4%, 95.9% and 88.2% compared with their static cultures. Compared with static culture, the carbohydrate contents of wild strain, 3-A10, 3-B2 and 4-B3 in pure air aeration culture system dropped plainly by 51.0%, 79.3%, 85.5% and 26.1%. Increase of CO2 concentration enhanced carbohydrate content and productivity. Based on the carbohydrate productivity, the optimal inlet of CO2 concentration in aeration culture was determined to be 12% (v/v). Under this condition, 3-B2 exhibited the highest carbohydrate content (30.7%), CO2 fixation rate (0.120gCO2·g(-1)·d(-1)) and higher growth rate (0.093 g L(-1)·d(-1)), while 3-A10 showed the highest growth rate (0.118 g L(-1)·d(-1)) and higher CO2 fixation rate (0.117gCO2·g(-1)·d(-1)) but low carbohydrate content (24.5%), and 4-B3 showed the highest chlorophyll (Chl) content (3.82 mg·g(-1)). The most outstanding mutant by static culture in terms of growth rate and carbohydrate productivity (3-B2), was also demonstrated by CO2 aeration culture system. This study revealed that the ARTP mutagenesis could generate the S. platensis mutants suitable for CO2 aeration culture aiming at biomass production. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Soil Aeration deficiencies in urban sites

NASA Astrophysics Data System (ADS)

Weltecke, Katharina; Gaertig, Thorsten

2010-05-01

Soil aeration deficiencies in urban sites Katharina Weltecke and Thorsten Gaertig On urban tree sites reduction of soil aeration by compaction or sealing is an important but frequently underestimated factor for tree growth. Up to 50% of the CO2 assimilated during the vegetation period is respired in the root space (Qi et al. 1994). An adequate supply of the soil with oxygen and a proper disposal of the exhaled carbon dioxide are essential for an undisturbed root respiration. If the soil surface is smeared, compacted or sealed, soil aeration is interrupted. Several references show that root activity and fine root growth are controlled by the carbon dioxide concentration in soil air (Qi et al.1994, Burton et al. 1997). Gaertig (2001) found that decreasing topsoil gas permeability leads to reduced fine root density and hence to injury in crown structure of oaks. In forest soils a critical CO2 concentration of more than 0.6 % indicates a bad aeration status (Gaertig 2001). The majority of urban tree sites are compacted or sealed. The reduction of soil aeration may lead to dysfunctions in the root space and consequently to stress during periods of drought, which has its visible affects in crown structure. It is reasonable to assume that disturbances in soil aeration lead to reduced tree vigour and roadworthiness, resulting in high maintenance costs. The assessment of soil aeration in urban sites is difficult. In natural ecosystems the measurement of gas diffusivity and the gas-chromatical analysis of CO2 in soil air are accepted procedures in analyzing the state of aeration (Schack-Kirchner et al. 2001, Gaertig 2001). It has been found that these methods can also be applied for analyzing urban sites. In particular CO2 concentration in the soil atmosphere can be considered as a rapidly assessable, relevant and integrating indicator of the aeration situation of urban soils. This study tested the working hypothesis that soil aeration deficiencies lead to a decrease of fine root density and tree vigour on urban soils. For that purpose gas diffusivity, soil CO2 concentrations and fine root density were measured on typical urban sites in the German cities of Göttingen, Mannheim, and Kassel. The known characteristics of soil aeration on forest sites could be affirmed for urban soils. A negative correlation was found between gas diffusion coefficients and CO2 concentration as well as between fine root extension and CO2 concentration. Changes in crown structure of beech indicating a loss of vigour were found at sites with disturbed aeration. Diffusivity patterns and CO2 concentrations of different specific urban soil sealing types were found. On more natural sites (mulch, grass) increased gas diffusion and low CO2 concentration were present. In contrast, on more compacted or sealed areas (asphalt, paving stone, macadamised road surface) the exchange between soil air and atmosphere was nearly disconnected and soil CO2 concentrations partly exceeded the known critical value of 0.6 % up to tenfold. Literature Burton, A. J.; Pregitzer, K. S.; Zogg, G. P. und Zak D. R. (1997): Effect of measurement CO2 concentrations on sugar maple root respiration. In: Canadian journal of Forest Research, H. 17, S. 421-427. Gaertig, T. (2001): Bodengashaushalt, Feinwurzeln und Vitalität von Eichen. In: Freiburger Bodenkundliche Abhandlungen, H. 40, S. 157. Qi, J.; Marshall, J. D.; Mattson, K. G. (1994): High soil carbon dioxide concentrations inhibit root respiration of Douglas fir. In: New Phytol., Jg. 128, H. 3, S. 435-442. Schack-Kirchner, H.; Gaertig, T.; Wilpert, K. v.; Hildebrand, E. E. (2001): A modified McIntyre and Phillip approach to measure top-soil gas diffusivity in-situ. In: J. Plant Nutr. Soil Sci., Jg. 164, S. 253-258.

A combined system of microbial fuel cell and intermittently aerated biological filter for energy self-sufficient wastewater treatment

PubMed Central

Dong, Yue; Feng, Yujie; Qu, Youpeng; Du, Yue; Zhou, Xiangtong; Liu, Jia

2015-01-01

Energy self-sufficiency is a highly desirable goal of sustainable wastewater treatment. Herein, a combined system of a microbial fuel cell and an intermittently aerated biological filter (MFC-IABF) was designed and operated in an energy self-sufficient manner. The system was fed with synthetic wastewater (COD = 1000 mg L−1) in continuous mode for more than 3 months at room temperature (~25 °C). Voltage output was increased to 5 ± 0.4 V using a capacitor-based circuit. The MFC produced electricity to power the pumping and aeration systems in IABF, concomitantly removing COD. The IABF operating under an intermittent aeration mode (aeration rate 1000 ± 80 mL h−1) removed the residual nutrients and improved the water quality at HRT = 7.2 h. This two-stage combined system obtained 93.9% SCOD removal and 91.7% TCOD removal (effluent SCOD = 61 mg L−1, TCOD = 82.8 mg L−1). Energy analysis indicated that the MFC unit produced sufficient energy (0.27 kWh m−3) to support the pumping system (0.014 kWh m−3) and aeration system (0.22 kWh m−3). These results demonstrated that the combined MFC-IABF system could be operated in an energy self-sufficient manner, resulting to high-quality effluent. PMID:26666392

Effect of synthetic iron colloids on the microbiological NH(4)(+) removal process during groundwater purification.

PubMed

Wolthoorn, Anke; Temminghoff, Erwin J M; van Riemsdijk, Willem H

2004-04-01

Subsurface aeration is used to oxidise Fe in situ in groundwater that is used to make drinking water potable. In a groundwater system with pH>7 subsurface aeration results in non-mobile Fe precipitate and mobile Fe colloids. Since originally the goal of subsurface aeration is to remove iron in situ, the formation of non-mobile iron precipitate, which facilitates the metal's removal, is the desired result. In addition to this intended effect, subsurface aeration may also strongly enhance the microbiological removal of ammonium (NH(4)(+)) in the purification station. Mobile iron colloids could be the link between subsurface aeration and the positive effect on the NH(4)(+) removal process. Therefore, the objective of this study was to assess whether synthetic iron colloids could improve the NH(4)(+) removal process. The effect of synthetic iron colloids on the NH(4)(+) removal process was studied using an artificial purification set-up on a laboratory scale. Columns that purified groundwater with or without added synthetic iron colloids were set up in duplicate. The results showed that the NH(4)(+) removal was significantly ( alpha = 0.05 ) increased in columns treated with the synthetic iron colloids. Cumulative after 4 months about 10% more NH(4)(+) was nitrified in the columns that was treated with the groundwater containing synthetic iron colloids. The results support the hypothesis that mobile iron colloids could be the link between subsurface aeration and the positive effect on the NH(4)(+) removal process.

Performance of intermittent aeration reactor on NH4-N removal from groundwater resources.

PubMed

Khanitchaidecha, W; Nakamura, T; Sumino, T; Kazama, F

2010-01-01

To study the effect of intermittent aeration period on ammonium-nitrogen (NH4-N) removal from groundwater resources, synthetic groundwater was prepared and three reactors were operated under different conditions--"reactor A" under continuous aeration, "reactor B" under 6 h intermittent aeration, and "reactor C" under 2 h intermittent aeration. To facilitate denitrification simultaneously with nitrification, "acetate" was added as an external carbon source with step-wise increase from 0.5 to 1.5 C/N ratio, where C stands for total carbon content in the system, and N for NH4-N concentration in the synthetic groundwater. Results show that complete NH4-N removal was obtained in "reactor B" and "reactor C" at 1.3 and 1.5 C/N ratio respectively; and partial NH4-N removal in "reactor A". These results suggest that intermittent aeration at longer interval could enhance the reactor performance on NH4-N removal in terms of efficiency and low external carbon requirement. Because of consumption of internal carbon by the process, less amount of external carbon is required. Further increase in carbon in a form of acetate (1.5 to 2.5 C/N ratios) increases removal rate (represented by reaction rate coefficient (k) of kinetic equation) as well as occurrence of free cells. It suggests that the operating condition at reactor B with 1.3 C/N ratio is more appropriate for long-term operation at a pilot-scale.

Enhancing nitrogen removal in an Orbal oxidation ditch by optimization of oxygen supply: practice in a full-scale municipal wastewater treatment plant.

PubMed

Zhou, Xin; Guo, Xuesong; Han, Yunping; Liu, Junxin; Ren, Jincheng; Wang, Yu; Guo, Yantao

2012-09-01

Seven different aeration modes, in which oxygen supply was changed by adjusting the number of aerators, were designed and applied in a full-scale municipal wastewater treatment plant with Orbal oxidation ditch to investigate the influence of dissolved oxygen (DO) on nitrogen removal performance. The full-scale experiment results of 574 days showed that nitrogen removal efficiency depended on the degree of nitrification and denitrification in the outer channel, which was the largest contributor for TN removal in the Orbal oxidation ditch. Appropriate aeration control in the outer channel was essential to balance nitrification and denitrification in the Orbal oxidation ditch. When DO was as low as about 0.2 mg/L in the outer channel, the highest TN removal efficiency of 75% was obtained. Microbial analysis confirmed that aerobic and anaerobic bacteria coexisted in the outer channel. The greater species diversity and more intensive activities of these bacteria in aeration Mode V may be responsible for the higher TN removal efficiency compared with Mode III. These results suggest that different aerated conditions in the Orbal oxidation ditch might have a significant effect on microbial community characteristics and nitrogen removal efficiencies.

Feasibility study of a V-shaped pipe for passive aeration composting.

PubMed

Ogunwande, Gbolabo A

2011-03-01

A V-shaped (Vs) pipe was improvised for composting of chicken litter in passive aeration piles. Three piles, equipped with horizontal (Ho), vertical (Ve) and Vs pipes were set up. The three treatments were replicated thrice. The effects of the aeration pipe on the physico-chemical properties of chicken litter and air distribution within the composting piles were investigated during composting. The properties monitored were temperature, pH, electrical conductivity, moisture content, total carbon, total nitrogen, total phosphorus and carbon-to-nitrogen ratio. Moisture level in the piles was replenished fortnightly to 60% during composting. The results of the study showed that all the piles attained the optimum temperature range (40-65°C) for effective composting and satisfied the requirements for sanitation. The non-significant (p > 0.05) temperature difference within the piles with Ve and Vs pipes indicated that these pipes were effective for uniform air distribution within the pile. The aeration pipe had significant (p ≤ 0.05) effect on pile temperature, pre-replenishment moisture content, pH and total phosphorus. In conclusion, the study showed that the Vs pipe is feasible and effective for passive aeration composting.

Effects of subsurface aeration and trinexapac-ethyl application on soil microbial communities in a creeping bentgrass putting green

USGS Publications Warehouse

Feng, Y.; Stoeckel, D.M.; Van Santen, E.; Walker, R.H.

2002-01-01

The sensitivity of creeping bentgrass (Agrostis palustris Huds.) to the extreme heat found in the southeastern United States has led to the development of new greens-management methods. The purpose of this study was to examine the effects of subsurface aeration and growth regulator applications on soil microbial communities and mycorrhizal colonization rates in a creeping bentgrass putting green. Two cultivars (Crenshaw and Penncross), a growth regulator (trinexapacethyl), and subsurface aeration were evaluated in cool and warm seasons. Total bacterial counts were higher in whole (unsieved) soils than in sieved soils, indicating a richer rhizosphere soil environment. Mycorrhizal infection rates were higher in trinexapac-ethyl (TE) treated plants. High levels of hyphal colonization and relatively low arbuscule and vesicle occurrence were observed. Principal components analysis of whole-soil fatty acid methyl ester (FAME) profiles indicated that warm-season microbial populations in whole and sieved soils had similar constituents, but the populations differed in the cool season. FAME profiles did not indicate that subsurface aeration and TE application affected soil microbial community structure. This is the first reported study investigating the influences of subsurface aeration and TE application on soil microorganisms in a turfgrass putting green soil.

Treatment of landfill leachate using an aerated, horizontal subsurface-flow constructed wetland.

PubMed

Nivala, J; Hoos, M B; Cross, C; Wallace, S; Parkin, G

2007-07-15

A pilot-scale subsurface-flow constructed wetland was installed at the Jones County Municipal Landfill, near Anamosa, Iowa, in August 1999 to demonstrate the use of constructed wetlands as a viable low-cost treatment option for leachate generated at small landfills. The system was equipped with a patented wetland aeration process to aid in removal of organic matter and ammonia nitrogen. The high iron content of the leachate caused the aeration system to cease 2 years into operation. Upon the installation of a pretreatment chamber for iron removal and a new aeration system, treatment efficiencies dramatically improved. Seasonal performance with and without aeration is reported for 5-day biochemical oxygen demand (BOD(5)), chemical oxygen demand (COD), ammonia nitrogen (NH(4)-N), and nitrate nitrogen (NO(3)-N). Since winter air temperatures in Iowa can be very cold, a layer of mulch insulation was installed on top of the wetland bed to keep the system from freezing. When the insulation layer was properly maintained (either through sufficient litterfall or replenishing the mulch layer), the wetland sustained air temperatures of as low as -26 degrees C without freezing problems.

Renewable energy for the aeration of wastewater ponds.

PubMed

Hobus, I; Hegemann, W

2003-01-01

The application of a decentralised renewable energy supply for the aeration of wastewater ponds, and the influence of an unsteady oxygen supply on the specific conversion rate and biocoenose was investigated. With the discontinuous aeration the specific conversion rate is increased as compared to facultative ponds. The estimation of the microorganisms consortia was done with in situ hybridisation techniques. A significant shift in the bacteria population with the chosen specific probes for anaerobic, sulphate reducing and nitrifying bacteria could not be detected. Wastewater ponds have sufficient buffer volume to compensate for the fluctuating energy supply. But the efficiency of the energy supply of a photovoltaic plant decreases in shallow lakes (d < 1.5 m) corresponding to a high oxygen production of algae. For the layout of the individual components: photovoltaic and wind power plant, energy management, aeration system and wastewater pond, a simulation model was developed and tested. The application of renewable energy for the aeration of wastewater ponds is a useful alternative for the redevelopment of overloaded ponds as well as the construction of new wastewater ponds, especially in areas with an inadequate central electricity grid and a high availability of wind and solar energy.

Effect of long-term successive storm flows on water reclamation plant resilience.

PubMed

Zhu, Jun-Jie; Anderson, Paul R

2017-03-15

A water reclamation plant (WRP) needs to be resilient to successfully operate through different kinds of perturbations. Perturbations such as storm events, especially long-term successive storm flows, can adversely affect operations. A better understanding of these effects can provide benefits for plant operation, in terms of effluent quality and energy efficiency. However, the concept of resilience for a WRP has not been widely studied, and we are not aware of any studies specifically related to storm flows. In this work we applied measures of resistance and recovery time to quantify resilience, and used a WRP simulation model to investigate how different storm flow characteristics (flowrate and duration) and the amount of aeration influence resilience. Not surprisingly, increasing storm flowrate leads to decreasing resilience. Although the aeration rate plays an important role in determining resilience, there is an aeration threshold (6 m 3 /s for our WRP model); higher aeration rates do not increase resilience. Results suggest that aeration costs could be reduced by as much as 50% while still maintaining the resilience needed to meet effluent quality permit requirements through the perturbations examined in this study. Copyright © 2016 Elsevier Ltd. All rights reserved.

A GUIDE TO AERATION/CIRCULATION TECHNIQUES FOR ...

EPA Pesticide Factsheets

The application of aeration/circulation techniques to lakes are reviewed from a theoretical and practical viewpoint. The effect of destratification on algal production is related to the mixed depth with the use of a mathematical model. Procedures are given to determine air required to mix lakes of different sizes and shapes. It was found that approximately 30 scfm of air per 1,000,000 sq ft of lake surface area can be used. Hypolimnetic aeration systems that have been used are described in detail. Procedures for design are given.

Turbulence and wave breaking effects on air-water gas exchange

PubMed

Boettcher; Fineberg; Lathrop

2000-08-28

We present an experimental characterization of the effects of turbulence and breaking gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration rates: turbulent transport when no wave breaking occurs and bubble dominated transport when wave breaking occurs. In both regimes, we correlate the qualitative changes in the aeration rate with corresponding changes in the wave dynamics. In the latter regime, the strongly enhanced aeration rate is correlated with measured acoustic emissions, indicating that bubble creation and dynamics dominate air-water exchange.

The effect of airflow rates and aeration mode on the respiration activity of four organic wastes: Implications on the composting process.

PubMed

Mejias, Laura; Komilis, Dimitrios; Gea, Teresa; Sánchez, Antoni

2017-07-01

The aim of this study was to assess the effect of the airflow and of the aeration mode on the composting process of non-urban organic wastes that are found in large quantities worldwide, namely: (i) a fresh, non-digested, sewage sludge (FSS), (ii) an anaerobically digested sewage sludge (ADSS), (iii) cow manure (CM) and (iv) pig sludge (PS). This assessment was done using respirometric indices. Two aeration modes were tested, namely: (a) a constant air flowrate set at three different initial fixed airflow rates, and (b) an oxygen uptake rate (OUR)-controlled airflow rate. The four wastes displayed the same behaviour namely a limited biological activity at low aeration, while, beyond a threshold value, the increase of the airflow did not significantly increase the dynamic respiration indices (DRI 1 max , DRI 24 max and AT 4 ). The threshold airflow rate varied among wastes and ranged from 42NL air kg -1 DMh -1 for CM and from 67 to 77NL air kg -1 DMh -1 for FSS, ADSS and PS. Comparing the two aeration modes tested (constant air flow, OUR controlled air flow), no statistically significant differences were calculated between the respiration activity indices obtained at those two aeration modes. The results can be considered representative for urban and non-urban organic wastes and establish a general procedure to measure the respiration activity without limitations by airflow. This will permit other researchers to provide consistent results during the measurement of the respiration activity. Results indicate that high airflows are not required to establish the maximum respiration activity. This can result in energy savings and the prevention of off-gas treatment problems due to the excessive aeration rate in full scale composting plants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Modelling the link amongst fine-pore diffuser fouling, oxygen transfer efficiency, and aeration energy intensity.

PubMed

Garrido-Baserba, Manel; Sobhani, Reza; Asvapathanagul, Pitiporn; McCarthy, Graham W; Olson, Betty H; Odize, Victory; Al-Omari, Ahmed; Murthy, Sudhir; Nifong, Andrea; Godwin, Johnnie; Bott, Charles B; Stenstrom, Michael K; Shaw, Andrew R; Rosso, Diego

2017-03-15

This research systematically studied the behavior of aeration diffuser efficiency over time, and its relation to the energy usage per diffuser. Twelve diffusers were selected for a one year fouling study. Comprehensive aeration efficiency projections were carried out in two WRRFs with different influent rates, and the influence of operating conditions on aeration diffusers' performance was demonstrated. This study showed that the initial energy use, during the first year of operation, of those aeration diffusers located in high rate systems (with solids retention time - SRT-less than 2 days) increased more than 20% in comparison to the conventional systems (2 > SRT). Diffusers operating for three years in conventional systems presented the same fouling characteristics as those deployed in high rate processes for less than 15 months. A new procedure was developed to accurately project energy consumption on aeration diffusers; including the impacts of operation conditions, such SRT and organic loading rate, on specific aeration diffusers materials (i.e. silicone, polyurethane, EPDM, ceramic). Furthermore, it considers the microbial colonization dynamics, which successfully correlated with the increase of energy consumption (r 2 :0.82 ± 7). The presented energy model projected the energy costs and the potential savings for the diffusers after three years in operation in different operating conditions. Whereas the most efficient diffusers provided potential costs spanning from 4900 USD/Month for a small plant (20 MGD, or 74,500 m 3 /d) up to 24,500 USD/Month for a large plant (100 MGD, or 375,000 m 3 /d), other diffusers presenting less efficiency provided spans from 18,000USD/Month for a small plant to 90,000 USD/Month for large plants. The aim of this methodology is to help utilities gain more insight into process mechanisms and design better energy efficiency strategies at existing facilities to reduce energy consumption. Copyright © 2016 Elsevier Ltd. All rights reserved.

Linking biofilm growth to fouling and aeration performance of fine-pore diffuser in activated sludge.

PubMed

Garrido-Baserba, Manel; Asvapathanagul, Pitiporn; McCarthy, Graham W; Gocke, Thomas E; Olson, Betty H; Park, Hee-Deung; Al-Omari, Ahmed; Murthy, Sudhir; Bott, Charles B; Wett, Bernhard; Smeraldi, Joshua D; Shaw, Andrew R; Rosso, Diego

2016-03-01

Aeration is commonly identified as the largest contributor to process energy needs in the treatment of wastewater and therefore garners significant focus in reducing energy use. Fine-pore diffusers are the most common aeration system in municipal wastewater treatment. These diffusers are subject to fouling and scaling, resulting in loss in transfer efficiency as biofilms form and change material properties producing larger bubbles, hindering mass transfer and contributing to increased plant energy costs. This research establishes a direct correlation and apparent mechanistic link between biofilm DNA concentration and reduced aeration efficiency caused by biofilm fouling. Although the connection between biofilm growth and fouling has been implicit in discussions of diffuser fouling for many years, this research provides measured quantitative connection between the extent of biofouling and reduced diffuser efficiency. This was clearly established by studying systematically the deterioration of aeration diffusers efficiency during a 1.5 year period, concurrently with the microbiological study of the biofilm fouling in order to understand the major factors contributing to diffuser fouling. The six different diffuser technologies analyzed in this paper included four different materials which were ethylene-propylene-diene monomer (EPDM), polyurethane, silicone and ceramic. While all diffusers foul eventually, some novel materials exhibited fouling resistance. The material type played a major role in determining the biofilm characteristics (i.e., growth rate, composition, and microbial density) which directly affected the rate and intensity at what the diffusers were fouled, whereas diffuser geometry exerted little influence. Overall, a high correlation between the increase in biofilm DNA and the decrease in αF was evident (CV < 14.0 ± 2.0%). By linking bacterial growth with aeration efficiency, the research was able to show quantitatively the causal connection between bacterial fouling and energy wastage during aeration. Copyright © 2015 Elsevier Ltd. All rights reserved.

ENHANCED BIODEGRADATION THROUGH IN-SITU AERATION

EPA Science Inventory

This presentation provided an overview of enhanced aerobic bioremediation using in-situ aeration or venting. The following topics were covered: (1) Basic discussion on biodegradation and respiration testing; (2) Basic discussion on volatilization, rate-limited mass transport, an...

DESIGN INFORMATION ON FINE PORE AERATION SYSTEMS

EPA Science Inventory

Field studies were conducted over several years at municipal wastewater treatment plants employing line pore diffused aeration systems. These studies were designed to produce reliable information on the performance and operational requirements of fine pore devices under process ...

Thermal Response Of An Aerated Concrete Wall With Micro-Encapsulated Phase Change Material

NASA Astrophysics Data System (ADS)

Halúzová, Dušana

2015-06-01

For many years Phase Change Materials (PCM) have attracted attention due to their ability to store large amounts of thermal energy. This property makes them a candidate for the use of passive heat storage. In many applications, they are used to avoid the overheating of the temperature of an indoor environment. This paper describes the behavior of phase change materials that are inbuilt in aerated concrete blocks. Two building samples of an aerated concrete wall were measured in laboratory equipment called "twin-boxes". The first box consists of a traditional aerated concrete wall; the second one has additional PCM micro-encapsulated in the wall. The heat flux through the wall was measured and compared to simulation results modeled in the ESP-r program. This experimental measurement provides a foundation for a model that can be used to analyze further building constructions.

Single chamber microbial fuel cell with Ni-Co cathode

NASA Astrophysics Data System (ADS)

Włodarczyk, Barbara; Włodarczyk, Paweł P.; Kalinichenko, Antonina

2017-10-01

The possibility of wastewater treatment and the parallel energy production using the Ni-Co alloy as cathode catalyst for single chamber microbial fuel cells is presented in this research. The research included a preparation of catalyst and comparison of COD, NH4+ and NO3- reduction in the reactor without aeration, with aeration and with using a single chamber microbial fuel cell with Ni-Co cathode. The reduction time for COD with the use of microbial fuel cell with the Ni-Co catalyst is similar to the reduction time with aeration. The current density (2.4 A·m-2) and amount of energy (0.48 Wh) obtained in MFC is low, but the obtained amount of energy allows elimination of the energy needed for reactor aeration. It has been shown that the Ni-Co can be used as cathode catalyst in single chamber microbial fuel cells.

[Research of aeration with bio-film technology to treat urban landscape water].

PubMed

Song, Ying-Wei; Nie, Zhi-Dan; Nian, Yue-Gang; Huang, Min-Sheng; Huang, Jian-Jun; Yan, Hai-Hong; Zhang, Yang

2008-01-01

Research of the aeration with bio-film technology was carried out to treat scenic water of a sanatorium in Beijing. The aim of the research was improving the water habitat by increasing the transparency and reducing the concentration of N and P. The equipments were set in a 5,000 m2 water area, which combined the plug flow jet aerator with the elastic biological filler. The research indicated that the transparency increased from 25 cm to 120 cm by the technology. The removal efficiencies of NH4(+)-N, NO3(-)-N and TP were 86.6% , 90% and 73.3%, but there was only 22.4% for TN. The concentration of DO increased from 4.3 mg/L to 7 mg/L. In a word, the aeration with bio-film technology was an effective measure to improve the water habitat by increasing the transparency.

Nitrous oxide from aerated dairy manure slurries: Effects of aeration rates and oxic/anoxic phasing.

PubMed

Molodovskaya, Marina; Singurindy, Olga; Richards, Brian K; Steenhuis, Tammo S

2008-12-01

Small-scale laboratory research was conducted to compare the effects of different aeration rates and oxic/anoxic phasing on nitrous oxide (N(2)O) formation from dairy manure slurries. Manure slurry samples were incubated in triplicate for three-weeks under a range of continuous sweep gas flows (0.01-0.23L min(-1)kg(-1) slurry) with and without oxygen (air and dinitrogen gas). The net release of N(2)O-N was affected by both aeration rates and oxic/anoxic conditions, whereas ammonia volatilization depended mainly on gas flow rates. Maximum N(2)O-N losses after three-weeks incubation were 4.2% of total slurry N. Major N losses (up to 50% of total slurry N) were caused by ammonia volatilization that increased with increasing gas flow rates. The lowest nitrous oxide and ammonia production was observed from low flow phased oxic/anoxic treatment.

Thermal Bridge Effect of Aerated Concrete Block Wall in Cold Regions

NASA Astrophysics Data System (ADS)

Li, Baochang; Guo, Lirong; Li, Yubao; Zhang, Tiantian; Tan, Yufei

2018-01-01

As a self-insulating building material which can meet the 65 percent energy-efficiency requirements in cold region of China, aerated concrete blocks often go moldy, frost heaving, or cause plaster layer hollowing at thermal bridge parts in the extremely cold regions due to the restrictions of environmental climate and construction technique. L-shaped part and T-shaped part of aerated concrete walls are the most easily influenced parts by thermal bridge effect. In this paper, a field test is performed to investigate the scope of the thermal bridge effect. Moreover, a heat transfer calculation model for L-shaped wall and T-shaped wall is developed. According to the simulation results, the temperature fields of the thermal bridge affected regions are simulated and analyzed. The research outputs can provide theoretical basis for the application of aerated concrete wall in extremely cold regions.

Prediction of alpha factor values for fine pore aeration systems.

PubMed

Gillot, S; Héduit, A

2008-01-01

The objective of this work was to analyse the impact of different geometric and operating parameters on the alpha factor value for fine bubble aeration systems equipped with EPDM membrane diffusers. Measurements have been performed on nitrifying plants operating under extended aeration and treating mainly domestic wastewater. Measurements performed on 14 nitrifying plants showed that, for domestic wastewater treatment under very low F/M ratios, the alpha factor is comprised between 0.44 and 0.98. A new composite variable (the Equivalent Contact Time, ECT) has been defined and makes it possible for a given aeration tank, knowing the MCRT, the clean water oxygen transfer coefficient and the supplied air flow rate, to predict the alpha factor value. ECT combines the effect on mass transfer of all generally accepted factors affecting oxygen transfer performances (air flow rate, diffuser submergence, horizontal flow). (c) IWA Publishing 2008.

Design of top covers supporting aerobic in situ stabilization of old landfills--an experimental simulation in lysimeters.

PubMed

Hrad, Marlies; Huber-Humer, Marion; Wimmer, Bernhard; Reichenauer, Thomas G

2012-12-01

Landfill aeration by means of low pressure air injection is a promising tool to reduce long term emissions from organic waste fractions through accelerated biological stabilization. Top covers that enhance methane oxidation could provide a simple and economic way to mitigate residual greenhouse gas emissions from in situ aerated landfills, and may replace off-gas extraction and treatment, particularly at smaller and older sites. In this respect the installation of a landfill cover system adjusted to the forced-aerated landfill body is of great significance. Investigations into large scale lysimeters (2 × 2 × 3m) under field conditions have been carried out using different top covers including compost materials and natural soils as a surrogate to gas extraction during active low pressure aeration. In the present study, the emission behaviour as well as the water balance performance of the lysimeters has been investigated, both prior to and during the first months of in situ aeration. Results reveal that mature sewage sludge compost (SSC) placed in one lysimeter exhibits in principle optimal ambient conditions for methanotrophic bacteria to enhance methane oxidation. Under laboratory conditions the mature compost mitigated CH(4) loadings up to 300 lCH(4)/m(2)d. In addition, the compost material provided high air permeability even at 100% water holding capacity (WHC). In contrast, the more cohesive, mineral soil cover was expected to cause a notably uniform distribution of the injected air within the waste layer. Laboratory results also revealed sufficient air permeability of the soil materials (TS-F and SS-Z) placed in lysimeter C. However, at higher compaction density SS-Z became impermeable at 100% WHC. Methane emissions from the reference lysimeter with the smaller substrate cover (12-52 g CH(4)/m(2)d) were significantly higher than fluxes from the other lysimeters (0-19 g CH(4)/m(2)d) during in situ aeration. Regarding water balance, lysimeters covered with compost and compost-sand mixture, showed the lowest leachate rate (18-26% of the precipitation) due to the high water holding capacity and more favourable plant growth conditions compared to the lysimeters with mineral, more cohesive, soil covers (27-45% of the precipitation). On the basis of these results, the authors suggest a layered top cover system using both compost material as well as mineral soil in order to support active low-pressure aeration. Conventional soil materials with lower permeability may be used on top of the landfill body for a more uniform aeration of the waste due to an increased resistance to vertical gas flow. A compost cover may be built on top of the soil cover underlain by a gas distribution layer to improve methane oxidation rates and minimise water infiltration. By planting vegetation with a high transpiration rate, the leachate amount emanating from the landfill could be further minimised. The suggested design may be particularly suitable in combination with intermittent in situ aeration, in the later stage of an aeration measure, or at very small sites and shallow deposits. The top cover system could further regulate water infiltration into the landfill and mitigate residual CH(4) emissions, even beyond the time of active aeration. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biological treatment of soils contaminated with hydrophobic organics using slurry- and solid-phase techniques

NASA Astrophysics Data System (ADS)

Cassidy, Daniel H.; Irvine, Robert L.

1995-10-01

Both slurry-phase and solid-phase bioremediation are effective ex situ soil decontamination methods. Slurrying is energy intensive relative to solid-phase treatment, but provides homogenization and uniform nutrient distribution. Limited contaminant bioavailability at concentrations above the required cleanup level reduces biodegradation rates and renders solid phase bioremediation more cost effective than complete treatment in a bio-slurry reactor. Slurrying followed by solid-phase bioremediation combines the advantages and minimizes the weaknesses of each treatment method when used alone. A biological treatment system consisting of slurrying followed by aeration in solid phase bioreactors was developed and tested in the laboratory using a silty clay loam contaminated with diesel fuel. The first set of experiments was designed to determine the impact of the water content and mixing time during slurrying on the rate an extent of contaminant removal in continuously aerated solid phase bioreactors. The second set of experiments compared the volatile and total diesel fuel removal in solid phase bioreactors using periodic and continuous aeration strategies. Results showed that slurrying for 1.5 hours at a water content less than saturation markedly increased the rate and extent of contaminant biodegradation in the solid phase bioreactors compared with soil having no slurry pretreatment. Slurrying the soil at or above its saturation moisture content resulted in lengthy dewatering times which prohibited aeration, thereby delaying the onset of biological treatment in the solid phase bioreactors. Results also showed that properly operated periodic aeration can provide less volatile contaminant removal and a grater fraction of biological contaminant removal than continuous aeration.

Inorganic nitrogen transformations in the treatment of landfill leachate with a high ammonium load: A case study.

PubMed

Parkes, Stephen D; Jolley, Dianne F; Wilson, Stephen R

2007-01-01

The inorganic nitrogen transformations occurring at a municipal waste leachate treatment facility were investigated. The treatment facility consisted of a collection well and an artificial wetland between two aeration ponds. The first aeration pond showed a decrease in ammonium (from 3480 (+/- 120) to 630(+/- 90) mg x L(-1)), a reduction in inorganic nitrogen load (3480 to 1680 mg N x L(-1)), and an accumulation of nitrite (< 1.3 mg-N x L(-1) in the collection well, to 1030 mg-N x L(-1)). Incomplete ammonium oxidation was presumably the result of the low concentration of carbonate alkalinity (approximately 2 mg x L(-1)), which may cause a limitation in the ammonium oxidation rate of nitrifiers. Low carbonate alkalinity levels may have been the result of stripping of CO(2) from the first aeration pond at the high aeration rates and low pH. Various chemodenitrification mechanisms are discussed as the reason for the reduction in the inorganic nitrogen load, including; the reduction of nitrite by iron (II) (producing various forms of gaseous nitrogen); and reactions involving nitrous acid. It is suggested that the accumulation of nitrite may be the result of inhibition of nitrite oxidizers by nitrous acid and low temperatures. Relative to the first aeration pond, the speciation and concentration of inorganic nitrogen was stable in the wetlands and 2nd aeration pond. The limited denitrification in the wetlands most probably occurred due to low concentrations of organic carbon, and short retention times.

EMMC process for combined removal of organics, nitrogen and an odor producing substance.

PubMed

Yang, P Y; Su, R; Kim, S J

2003-12-01

In order to improve the process performance regarding the removal of organics, nitrogen, and an odor-causing compound (sulfide) contained in domestic wastewater, an entrapped-mixed-microbial cell (EMMC) with and without humic substances for both fixed and moving carrier reactors and conventional suspended growth culture (i.e. conventional activated sludge process) were investigated simultaneously. Both synthetic (simulated to the organics concentration of general domestic sewage) and actual domestic wastewater were investigated under operational conditions of 12 h of hydraulic retention time (HRT) with 1 h of aeration and 1 h of non-aeration, and 6 h of HRT with continuous aeration, at a room temperature of 25 +/- 2 degrees C. It was found that entrapping humic substances in the EMMC carriers had no impact on the removal of organics, nitrogen, and the odor-producing compound. Additionally, the performance of the EMMC moving carrier system for the removal of these pollutants is similar to that of the EMMC fixed carrier system. In general, the EMMC associated systems which provide high solids retention time achieve a better removal of chemical oxygen demand (COD), nitrogen, and the odor-producing substance than the suspended growth system for both HRTs of 6 h (continuous aeration) and 12 h (1 h of aeration and 1 h of non-aeration). Both the fixed and moving carrier EMMC processes, therefore, have the potential for improvement or replacement of the existing conventional activated sludge process with regard to improving the effluent qualities (such as COD, nitrogen and odor-producing compound) for reuse/disposal.

Oxygen microprofiles within the sediment-water interface studied by optode and its implication for aeration of polluted urban rivers.

PubMed

Liu, Bo; Han, Rui-Ming; Wang, Wen-Lin; Yao, Hong; Zhou, Feng

2017-04-01

To reveal the detailed vertical oxygen distribution at the sediment-water interface (SWI) and its relation with the oxygen consumption processes during and after aeration of polluted urban rivers, experimental systems constructed with collected sediment and in situ overlying water from a polluted urban river were aerated above or beneath the sediment-water interface 12 h a day for 15 days and left nonaerated for the following 10 days. The results showed that aeration of water or sediment both increased dissolved oxygen (DO) concentrations in the SWI, characterized by shifts in a "decrease-increase-decrease" manner during around 3 h for the aeration of water treatment (AW) and 6 h for the aeration of sediment treatment (AS). The oxygen penetration depth for AS experiments was between 0.66 and 4.16 mm with an average of 1.79 mm, significantly higher than that for AW experiments; however, the oxygen dissipation constant (mm -1 ) measuring the decay rate of DO near the SWI was greater for the AW experiments than the AS experiments. During the 10-day nonaeration period, the accumulation of nitrate in both the overlying water and sediment was greatly increased concomitantly with the higher oxygenation in AS experiments. From the nitrogen removal viewpoint, these results suggest that the SWI needs moderate oxygenation which enables nitrate and nitrite to be removed by denitrification rather than to be totally nitrified and accumulate as would result from the conventional practice by singly elevating DO concentrations.

Combination of Methoprene and Controlled Aeration to Manage Insects in Stored Wheat.

PubMed

Liu, Samuel S; Arthur, Frank H; VanGundy, Douglas; Phillips, Thomas W

2016-06-17

A commercial formulation of the insect growth regulator methoprene was applied to wheat stored in small bins either alone or in combination with controlled aeration of the bins, to lower grain temperature for insect pest management of stored wheat. Grain temperatures were monitored and modified by a computer-controlled thermocouple system that also activated the aeration system at programmed set-points to move cool ambient air through the grain mass to lower grain temperature. Results from sampling insect populations in experimental storage bins along with laboratory mortality bioassays of insects placed on wheat taken from the bins over the course of the storage period showed that methoprene was very effective in controlling infestation by the externally-feeding stored grain insects Plodia interpunctella (Hübner), the Indian meal moth Tribolium castaneum (Herbst), the red flour beetle, Cryptolestes ferrugineus (Stephens), the rusty grain beetle, and also for the internal-feeding pest Rhyzopertha dominica( Fauvel), the lesser grain borer. Methoprene did not give good control of the internal-feeding pest Sitophilus oryzae (L.), the rice weevil. Aeration alone was somewhat effective in suppressing insect population development, while methoprene alone or when combined with aeration greatly enhanced insect control. Commercial grain grading for industry quality standards at the end of the storage period confirmed the impact of insect suppression on maintaining high quality of the stored wheat. This field experiment shows that methoprene combined with aeration to cool grain can be effective for pest management of stored wheat in the southern plains of the United States of America.

Proof of live birth using postmortem multislice computed tomography (pmMSCT) in cases of suspected neonaticide: advantages of diagnostic imaging compared to conventional autopsy.

PubMed

Guddat, Saskia S; Gapert, René; Tsokos, Michael; Oesterhelweg, Lars

2013-03-01

Proof of live birth is of major importance in suspected neonaticide cases. Although not without controversy the lung flotation test is the main method used to asses this in different jurisdictions worldwide. The present study examines the usefulness of postmortem multislice computed tomography (pmMSCT) in the detection of live birth signs. Body scans were conducted on four infants, one was stillborn, another died a day after birth and the other two were classified as neonaticides. The appearance of the lungs, gastrointestinal tract and vascular system of the liver was compared in these cases. Clear differences were discernable between the lungs of the stillborn and the 1 day old infant. The aerated lungs and air in the stomach and duodenum were clearly visible in the latter case while the stillborn infant lacked these signs. The two neonaticide cases demonstrated similarly aerated lung tissue to the 1 day old infant. The hepatic vessels did not show any putrefactive gas changes in any of the cases. The extent of aeration of the peripheral alveoli was easily observable on the pmMSCT, thus making it a useful tool in the possible differentiation between artificially and naturally aerated lungs. During the four autopsies the classic flotation tests were performed and similar positive aeration of the lungs in the two neonaticides was shown. The stillborn's tests, on the other hand were negative for aeration. The results of this study clearly demonstrate the advantages of using pmMSCT before commencing a conventional autopsy in cases of suspected neonaticide.

INVESTIGATIONS INTO BIOFOULING PHENOMENA IN FINE PORE AERATION DEVICES

EPA Science Inventory

Microbiologically-based procedures were used to describe biofouling phenomena on fine pore aeration devices and to determine whether biofilm characteristics could be related to diffuser process performance parameters. Fine pore diffusers were obtained from five municipal wastewa...

T.A. BROWN MECHANICAL AERATOR

EPA Science Inventory

Students in the Environmental Engineering and Waster Resources capstone design class in the Department of Civil and Environmental Engineering will undertake a project in conjunction with Serasih Indonesia to develop a prototype mechanical aerator to be used in aquaculture live...

72. (Credit LSU) Aerator in settling basin south of McNeil ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

72. (Credit LSU) Aerator in settling basin south of McNeil Pumping Station c1907. (Louisiana State University in Shreveport Archives, post card collection) - McNeil Street Pumping Station, McNeil Street & Cross Bayou, Shreveport, Caddo Parish, LA

Dynamics of microbial growth and metabolic activity and their control by aeration.

PubMed

Kalina, V

1993-01-01

The optimization of fermentation processes depends to a large extent on the modelling of microbial activity under complex environmental conditions where aeration is an important limiting and control factor. Simple relationships are used to establish the sensitivity of cultures to oxygen stress. Specific limitation coefficients which can be determined in laboratory reactors allow a projection to industrial operation and the definition of appropriate aeration and agitation profiles. Optimum control can be assured on the basis of directly measurable process parameters. This is shown for the case of ethanol production using S. cerevisiae at high cell dry weight concentrations.

Removal of iron and manganese by artificial destratification in a tropical climate (Upper Layang Reservoir, Malaysia).

PubMed

Ismail, R; Kassim, M A; Inman, M; Baharim, N H; Azman, S

2002-01-01

Environmental monitoring was carried out at Upper Layang Reservoir situated in Masai, Johor, Malaysia. The study shows that thermal stratification and natural mixing of the water column do exist in the reservoir and the level of stratification varies at different times of the year. Artificial destratification via diffused air aeration techniques was employed at the reservoir for two months. The results show that thermal stratification was eliminated after a week of continuous aeration. The concentrations of iron and to a lesser extent manganese in the water column was also reduced during the aeration period.

Quality evaluation of carbonaceous industrial by-products and its effect on properties of autoclave aerated concrete

NASA Astrophysics Data System (ADS)

Fomina, E. V.; Lesovik, V. S.; Fomin, A. E.; Kozhukhova, N. I.; Lebedev, M. S.

2018-03-01

Argillite is a carbonaceous industrial by-product that is a potential source in environmentally friendly and source-saving construction industry. In this research, chemical and mineral composition as well as particle size distribution of argillite were studied and used to develop autoclave aerated concrete as partial substitute of quartz sand. Effect of the argillite as a mineral admixture in autoclave aerated concrete was investigated in terms of compressive and tensile strength, density, heat conductivity etc. The obtained results demonstrated an efficiency of argillite as an energy-saving material in autoclave construction composites.

Incorporation of air into a snack food reduces energy intake.

PubMed

Osterholt, Kathrin M; Roe, Liane S; Rolls, Barbara J

2007-05-01

This study investigated how the air content of a familiar snack food affected energy intake and whether varying the method of serving the snack modified intake. We tested two versions of an extruded snack (cheese puffs) that were equal in energy density (5.7 kcal/g), but differed in energy per volume (less-aerated snack: 1.00 kcal/ml; more-aerated snack: 0.45 kcal/ml). In a within-subjects design, 16 women and 12 men consumed the snacks ad libitum in the laboratory during four afternoon sessions. A standard volume (1250 ml) of each snack was served once in a bowl and once in an opaque bag. Results showed significant differences in intake of the two snacks by energy (p=0.0003) and volume (p<0.0001); subjects consumed 21% less weight and energy (70+/-17 kcal) of the more-aerated snack than the less-aerated snack, although they consumed a 73% greater volume of the more-aerated snack (239+/-24 ml). These findings suggest that subjects responded to both the weight and volume of the snack. Despite differences in intake, hunger and fullness ratings did not differ across conditions. The serving method did not significantly affect intake. Results from this study indicate that incorporating air into food provides a strategy to reduce energy intake from energy-dense snacks.

Effect of aeration rate, moisture content and composting period on availability of copper and lead during pig manure composting.

PubMed

Shen, Yujun; Zhao, Lixin; Meng, Haibo; Hou, Yueqing; Zhou, Haibin; Wang, Fei; Cheng, Hongsheng; Liu, Hongbin

2016-06-01

Pollution by heavy metals, such as copper and lead, has become a limiting factor for the land application of faecal manures, such as pig manure. This study was conducted to investigate the influence of composting process parameters, including aeration rate, moisture content and composting period, on the distribution of heavy metal species during composting, and to select an optimal parameter for copper and lead inactivation. Results showed that the distribution ratios of exchangeable fractions of copper and lead had a bigger decrease under conditions of aeration rate, 0.1 m(3) min(-1) m(-3), an initial moisture content of 65% and composting period of 50 days. Suboptimal composting process conditions could lead to increased availability of heavy metals. Statistical analysis indicated that the aeration rate was the main factor affecting copper and lead inactivation, while the effects of moisture content and composting period were not significant. The rates of reduction of copper-exchangeable fractions and lead-exchangeable fractions were positively correlated with increased pH. The optimal parameters for reducing heavy metal bioavailability during pig manure composting were aeration rate, 0.1 m(3) min(-1) m(-3), initial moisture content, 65%, and composting period, 20 days. © The Author(s) 2016.

CFD Investigation of the effects of bubble aerator layouts on hydrodynamics of an activated sludge channel reactor.

PubMed

Hreiz, Rainier; Potier, Olivier; Wicks, Jim; Commenge, Jean-Marc

2018-03-08

In this paper, computational fluid dynamics (CFD) simulations are employed to characterize the effects of bubble aerator layouts (i.e. spatial arrangement) on the hydrodynamics in activated sludge (AS) reactors. The first configuration considered is a channel reactor with aerators placed alongside one lateral wall, for which velocity measurements are available in literature. CFD results were in good agreement with experimental data, which proves that the model is sufficiently accurate and predictive. Accordingly, simulations and numerical residence time distribution tests were conducted for different aerator layouts to determine their effects on the reactor hydrodynamics. The results revealed that the flow characteristics are extremely sensitive to the aerators arrangement given the high gas flow rates used in AS processes. Among the layouts investigated, the one where diffusers are placed all over the reactor floor has led to the least dispersive flow, i.e. which characteristics best tend toward that of an ideal plug flow reactor. Indeed, this flow field presented the lowest average turbulent diffusion and the most uniform axial velocity and turbulence fields. Such a flow behaviour is expected to be highly beneficial for biological treatment since it reduces pollutant dilution by axial diffusion and limits raw wastewater channelling to the outlet.

Optimization of high-rate TN removal in a novel constructed wetland integrated with microelectrolysis system treating high-strength digestate supernatant.

PubMed

Guo, Luchen; He, Keli; Wu, Shubiao; Sun, Hao; Wang, Yanfei; Huang, Xu; Dong, Renjie

2016-08-01

The potential of high-rate TN removal in three aerated horizontal subsurface-flow constructed wetlands to treat high-strength anaerobic digestate supernatant was evaluated. Different strategies of intermittent aeration and effluent recirculation were applied to compare their effect on nitrogen depuration performance. Additional glucose supply and iron-activated carbon based post-treatment systems were established and examined, respectively, to further remove nitrate that accumulated in the effluents from aerated wetlands. The results showed that intermittent aeration (1 h on:1 h off) significantly improved nitrification with ammonium removal efficiency of 90% (18.1 g/(m(2)·d)), but limited TN removal efficiency (53%). Even though effluent recirculation (a ratio of 1:1) increased TN removal from 53% to 71%, the effluent nitrate concentration was still high. Additional glucose was used as a post-treatment option and further increased the TN removal to 82%; however, this implementation caused additional organic pollution. Furthermore, the iron-activated carbon system stimulated with a microelectrolysis process achieved greater than 85% effluent nitrate removal and resulted in 86% TN removal. Considering the high TN removal rate, aerated constructed wetlands integrated with a microelectrolysis-driven system show great potential for treating high-strength digestate supernatant. Copyright © 2016 Elsevier Ltd. All rights reserved.

Integral parameters for characterizing water, energy, and aeration properties of soilless plant growth media

NASA Astrophysics Data System (ADS)

Chamindu Deepagoda, T. K. K.; Chen Lopez, Jose Choc; Møldrup, Per; de Jonge, Lis Wollesen; Tuller, Markus

2013-10-01

Over the last decade there has been a significant shift in global agricultural practice. Because the rapid increase of human population poses unprecedented challenges to production of an adequate and economically feasible food supply for undernourished populations, soilless greenhouse production systems are regaining increased worldwide attention. The optimal control of water availability and aeration is an essential prerequisite to successfully operate plant growth systems with soilless substrates such as aggregated foamed glass, perlite, rockwool, coconut coir, or mixtures thereof. While there are considerable empirical and theoretical efforts devoted to characterize water retention and aeration substrate properties, a holistic, physically-based approach considering water retention and aeration concurrently is lacking. In this study, the previously developed concept of integral water storage and energy was expanded to dual-porosity substrates and an analog integral oxygen diffusivity parameter was introduced to simultaneously characterize aeration properties of four common soilless greenhouse growth media. Integral parameters were derived for greenhouse crops in general, as well as for tomatoes. The integral approach provided important insights for irrigation management and for potential optimization of substrate properties. Furthermore, an observed relationship between the integral parameters for water availability and oxygen diffusivity can be potentially applied for the design of advanced irrigation and management strategies to ensure stress-free growth conditions, while conserving water resources.

Respirator triggering of electron beam computed tomography (EBCT): evaluation of dynamic changes during mechanical expiration in the traumatized patient

NASA Astrophysics Data System (ADS)

Recheis, Wolfgang A.; Kleinsasser, Axel; Hatschenberger, Robert; Knapp, Rudolf; zur Nedden, Dieter; Hoermann, Christoph

1999-05-01

The purpose of this project is to evaluate the dynamic changes during expiration at different levels of positive end- expiratory pressure (PEEP) in the ventilated patient. We wanted to discriminate between normal lung function and acute respiratory distress syndrome (ARDS). After approval by the local Ethic Committee we studied two ventilated patients: (1) with normal lung function; (2) ARDS). We used the 50 ms scan mode of the EBCT. The beam was positioned 1 cm above the diaphragm. The table position remained unchanged. An electronic trigger was developed, that utilizes the respirators synchronizing signal to start the EBCT at the onset of expiration. During controlled mechanical expiration at two levels of PEEP (0 and 15 cm H2O), pulmonary aeration was rated as: well-aerated (-900HU/-500HU), poorly- aerated (-500HU/-100HU) and non-aerated (-100HU/+100HU). Pathological and normal lung function showed different dynamic changes (FIG.4-12). The different PEEP levels resulted in a significant change of pulmonary aeration in the same patient. Although we studied only a very limited number of patients, respirator triggered EBCT may be accurate in discriminating pathological changes due to the abnormal lung function in the mechanically ventilated patient.

FINE PORE DIFFUSER SYSTEM EVALUATION FOR THE GREEN BAY METROPOLITAN SEWERAGE DISTRICT

EPA Science Inventory

The Green Bay Metropolitan Sewerage District retrofitted two quadrants of their activated sludge aeration system with ceramic and membrane fine pore diffusers to provide savings in energy usage compared to the sparged turbine aerators originally installed. Because significant di...

40 CFR 63.361 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS FOR SOURCE CATEGORIES Ethylene Oxide Emissions Standards... used to facilitate off-gassing of ethylene oxide at a sterilization facility. Aeration room vent means the point(s) through which the evacuation of ethylene oxide-laden air from an aeration room occurs...

Two-Level factorial screening of new plasmid/strain combinations for prodution of recombinant-DNA products.

PubMed

Emborg, C; Jepsen, P K; Biedermann, K

1989-05-01

This article treats the basic problem of selection of experimental conditions for microbiological experiments for evaluation of newly isolated bacterial strains, mutants, or plasmid/strain combinations. For this purpose shake flask experiments in a 2(10-4)confounded factorial design at resolution IV with four blocks of 16 flasks were used. The design was used for testing of two new strain/plasmid combinations (E. coli MT 102/403-SD2 and W 3110/403-SD2) i.e., both strains with the same plasmid 403-SD2. Both strains were integrated in the design, so both strains were tested with nine factors (temperature, aeration, glucose, initial pH, pH regulation, reduced aeration, chloramphenicol, acetate, and glycerol). With both strains the interaction between initial pH and reduced aeration had a significant influence on the yield of the recombinant-DNA product nuclease. There was more than a factor of 10 between lowest and highest yield of product. In this interactive system the strains reacted differently. MT 102/403-SD2 had highest yields at high initial pH (8.4) and no reduction in aeration, whereas W 3110/403-SD2 had highest yields of nuclease at low initial pH (7.4) and reduced aeration (rubber stopper inserted after cultivation for 12 h). These data (and previous work) clearly demonstrate that it is impossible to suggest a simple set of experimental conditions for testing of new plasmid/strain combinations. It is clear that the exclusive application of a standardized growth technique e.g., LB-medium at 37 degrees C at an unspecified and uncontrolled aeration level, may lead to wrong conclusions on properties and potentials of now plasmid/strain combinations and may lead to rejection of useful strains or plasmids.

Spatiotemporal Aeration and Lung Injury Patterns Are Influenced by the First Inflation Strategy at Birth.

PubMed

Tingay, David G; Rajapaksa, Anushi; Zonneveld, C Elroy; Black, Don; Perkins, Elizabeth J; Adler, Andy; Grychtol, Bartłomiej; Lavizzari, Anna; Frerichs, Inéz; Zahra, Valerie A; Davis, Peter G

2016-02-01

Ineffective aeration during the first inflations at birth creates regional aeration and ventilation defects, initiating injurious pathways. This study aimed to compare a sustained first inflation at birth or dynamic end-expiratory supported recruitment during tidal inflations against ventilation without intentional recruitment on gas exchange, lung mechanics, spatiotemporal regional aeration and tidal ventilation, and regional lung injury in preterm lambs. Lambs (127 ± 2 d gestation), instrumented at birth, were ventilated for 60 minutes from birth with either lung-protective positive pressure ventilation (control) or as per control after either an initial 30 seconds of 40 cm H2O sustained inflation (SI) or an initial stepwise end-expiratory pressure recruitment maneuver during tidal inflations (duration 180 s; open lung ventilation [OLV]). At study completion, molecular markers of lung injury were analyzed. The initial use of an OLV maneuver, but not SI, at birth resulted in improved lung compliance, oxygenation, end-expiratory lung volume, and reduced ventilatory needs compared with control, persisting throughout the study. These changes were due to more uniform inter- and intrasubject gravity-dependent spatiotemporal patterns of aeration (measured using electrical impedance tomography). Spatial distribution of tidal ventilation was more stable after either recruitment maneuver. All strategies caused regional lung injury patterns that mirrored associated regional volume states. Irrespective of strategy, spatiotemporal volume loss was consistently associated with up-regulation of early growth response-1 expression. Our results show that mechanical and molecular consequences of lung aeration at birth are not simply related to rapidity of fluid clearance; they are also related to spatiotemporal pressure-volume interactions within the lung during inflation and deflation.

[Effect of Aeration Strategies on Emissions of Nitrogenous Gases and Methane During Sludge Bio-Drying].

PubMed

Qi, Lu; Wei, Yuan-song; Zhang, Jun-ya; Zhao, Chen-yang; Cai, Xing; Zhang, Yuan-li; Shao, Chun-yan; Li, Hong-mei

2016-01-15

The data on nitrogen gas (NH3, N2O, NO) emissions during sludge bio-drying process in China is scarce, especially NO due to its unstable chemical property. In this study, effect of two aeration modes on emissions of methane and nitrogenous gas was compared during the continuous aerated turning pile sludge bio-drying process at full scale. In these two aeration strategies, the one currently used in the plant was set as the control, and the other was set as the test in which the aeration was used for oxygen supply, pile temperature control, and moisture removal in the start-up, middle and final stages, respectively. The results showed that the aeration strategy used in the test could not only obviously accelerate the rate of sludge drying (the moisture contents of the test and the control were 36.6% and 42% on day 11) , but also had a better drying performance (the final moisture contents of the test and the control were 33.6% and 37.6%, respectively) and decreased the ammonia cumulative emission by 5%, (ammonia cumulative emission of the test and the control were 208 mg x m(-3) and 219.8 mg x m(-3), respectively). Though a lower accumulated emission (eCO2) of greenhouse gas in the test at 3.61 kg x t(-1) was observed than that of the control (3.73 kg x t(-1) dry weight) , the cumulative emission of NO in the test at 1.9 g x m(-2) was 15. 9% higher than that of the control (1.6 g x m(-2)).

Control of nitrification/denitrification in an onsite two-chamber intermittently aerated membrane bioreactor with alkalinity and carbon addition: Model and experiment.

PubMed

Perera, Mahamalage Kusumitha; Englehardt, James D; Tchobanoglous, George; Shamskhorzani, Reza

2017-05-15

Denitrifying membrane bioreactors (MBRs) are being found useful in water reuse treatment systems, including net-zero water (nearly closed-loop), non-reverse osmosis-based, direct potable reuse (DPR) systems. In such systems nitrogen may need to be controlled in the MBR to meet the nitrate drinking water standard in the finished water. To achieve efficient nitrification and denitrification, the addition of alkalinity and external carbon may be required, and control of the carbon feed rate is then important. In this work, an onsite, two-chamber aerobic nitrifying/denitrifying MBR, representing one unit process of a net-zero water, non-reverse osmosis-based DPR system, was modeled as a basis for control of the MBR internal recycling rate, aeration rate, and external carbon feed rate. Specifically, a modification of the activated sludge model ASM2dSMP was modified further to represent the rate of recycling between separate aerobic and anoxic chambers, rates of carbon and alkalinity feed, and variable aeration schedule, and was demonstrated versus field data. The optimal aeration pattern for the modeled reactor configuration and influent matrix was found to be 30 min of aeration in a 2 h cycle (104 m 3 air/d per 1 m 3 /d average influent), to ultimately meet the nitrate drinking water standard. Optimal recycling ratios (inter-chamber flow to average daily flow) were found to be 1.5 and 3 during rest and mixing periods, respectively. The model can be used to optimize aeration pattern and recycling ratio in such MBRs, with slight modifications to reflect reactor configuration, influent matrix, and target nitrogen species concentrations, though some recalibration may be required. Copyright © 2017 Elsevier Ltd. All rights reserved.

Aeration optimization through operation at low dissolved oxygen concentrations: Evaluation of oxygen mass transfer dynamics in different activated sludge systems.

PubMed

Fan, Haitao; Qi, Lu; Liu, Guoqiang; Zhang, Yuankai; Fan, Qiang; Wang, Hongchen

2017-05-01

In wastewater treatment plants (WWTPs) using the activated sludge process, two methods are widely used to improve aeration efficiency - use of high-efficiency aeration devices and optimizing the aeration control strategy. Aeration efficiency is closely linked to sludge characteristics (such as concentrations of mixed liquor suspended solids (MLSS) and microbial communities) and operating conditions (such as air flow rate and operational dissolved oxygen (DO) concentrations). Moreover, operational DO is closely linked to effluent quality. This study, which is in reference to WWTP discharge class A Chinese standard effluent criteria, determined the growth kinetics parameters of nitrifiers at different DO levels in small-scale tests. Results showed that the activated sludge system could meet effluent criteria when DO was as low as 0.3mg/L, and that nitrifier communities cultivated under low DO conditions had higher oxygen affinity than those cultivated under high DO conditions, as indicated by the oxygen half-saturation constant and nitrification ability. Based on nitrifier growth kinetics and on the oxygen mass transfer dynamic model (determined using different air flow rate (Q' air ) and mixed liquor volatile suspended solids (MLVSS) values), theoretical analysis indicated limited potential for energy saving by improving aeration diffuser performance when the activated sludge system had low oxygen consumption; however, operating at low DO and low MLVSS could significantly reduce energy consumption. Finally, a control strategy coupling sludge retention time and MLVSS to minimize the DO level was discussed, which is critical to appropriate setting of the oxygen point and to the operation of low DO treatment technology. Copyright © 2016. Published by Elsevier B.V.

Stepped chute training wall height requirements

USDA-ARS?s Scientific Manuscript database

Stepped chutes are commonly used for overtopping protection for embankment dams. Aerated flow is commonly associated with stepped chutes if the chute has sufficient length. The aeration and turbulence of the flow can create a significant amount of splash over the training wall if not appropriately...

[Quick Start-up and Sustaining of Shortcut Nitrification in Continuous Flow Reactor].

PubMed

Wu, Peng; Zhang Shi-ying; Song, Yin-ling; Xu, Yue-zhong; Shen, Yao-liang

2016-04-15

How to achieve fast and stable startup of shortcut nitrification has a very important practical value for treatment of low C/N ratio wastewater. Thus, the quick start-up and sustaining of shortcut nitrification were investigated in continuous flow reactor targeting at the current situation of urban wastewater treatment plant using a continuous flow process. The results showed that quick start-up of shortcut nitrification could be successfully achieved in a continuous flow reactor after 60 days' operation with intermittent aeration and controlling of three stages of stop/aeration time (15 min/45 min, 45 min/45 min and 30 min/30 min). The nitrification rates could reach 90% or 95% respectively, while influent ammonia concentrations were 50 or 100 mg · L⁻¹ with stop/aeration time of 30 min/30 min. In addition, intermittent aeration could inhibit the activity of nitrite oxidizing bacteria (NOB), while short hydraulic retention time (HRT) may wash out NOB. And a combined use of both measures was beneficial to sustain shortcut nitrification.

Improving industrial full-scale production of baker's yeast by optimizing aeration control.

PubMed

Blanco, Carlos A; Rayo, Julia; Giralda, José M

2008-01-01

This work analyzes the control of optimum dissolved oxygen of an industrial fed-batch procedure in which baker's yeast (Saccharomyces cerevisiae) is grown under aerobic conditions. Sugar oxidative metabolism was controlled by monitoring aeration, molasses flows, and yeast concentration in the propagator along the later stage of the propagation, and keeping pH and temperature under controlled conditions. A large number of fed-batch growth experiments were performed in the tank for a period of 16 h, for each of the 3 manufactured commercial products. For optimization and control of cultivations, the growth and metabolite formation were quantified through measurement of specific growth and ethanol concentration. Data were adjusted to a model of multiple lineal regression, and correlations representing dissolved oxygen as a function of aeration, molasses, yeast concentration in the broth, temperature, and pH were obtained. The actual influence of each variable was consistent with the mathematical model, further justified by significant levels of each variable, and optimum aeration profile during the yeast propagation.

Simulation of water removal process and optimization of aeration strategy in sewage sludge composting.

PubMed

Zhou, Hai-Bin; Chen, Tong-Bin; Gao, Ding; Zheng, Guo-Di; Chen, Jun; Pan, Tian-Hao; Liu, Hong-Tao; Gu, Run-Yao

2014-11-01

Reducing moisture in sewage sludge is one of the main goals of sewage sludge composting and biodrying. A mathematical model was used to simulate the performance of water removal under different aeration strategies. Additionally, the correlations between temperature, moisture content (MC), volatile solids (VS), oxygen content (OC), and ambient air temperature and aeration strategies were predicted. The mathematical model was verified based on coefficients of correlation between the measured and predicted results of over 0.80 for OC, MC, and VS, and 0.72 for temperature. The results of the simulation showed that water reduction was enhanced when the average aeration rate (AR) increased to 15.37 m(3) min(-1) (6/34 min/min, AR: 102.46 m(3) min(-1)), above which no further increase was observed. Furthermore, more water was removed under a higher on/off time of 7/33 (min/min, AR: 87.34 m(3) min(-1)), and when ambient air temperature was higher. Copyright © 2014 Elsevier Ltd. All rights reserved.

The role of oxygen in the liquid fermentation of wheat bran.

PubMed

Savolainen, Otto I; Coda, Rossana; Suomi, Katja; Katina, Kati; Juvonen, Riikka; Hanhineva, Kati; Poutanen, Kaisa

2014-06-15

The extensive use of wheat bran as a food ingredient is limited due to its bitter taste and hard texture. To overcome these, some preprocessing methods, such as fermentation with yeast and lactic acid bacteria or enzymatic treatments have been proposed. The current work studied microbial communities, acidification, ethanol formation and metabolite profile of wheat bran fermented in either aerated or anaerobic conditions. In aerated conditions, yeasts grew better and the production of organic acids was smaller, and hence pH was higher. In anaerobic conditions, lactic acid bacteria and endogenous heterotrophic bacteria grew better. Aeration had a large effect on the sourdough metabolite profile, as analyzed by UPLC-qTOF-MS. Anaerobic conditions induced degradation of ferulic and caffeic acids, whereas the amount of sinapic acid increased. Aeration caused degradation of amino acids and hydroxycinnamic acid derivatives of polyamines. The results suggest that the control of oxygen could be used for tailoring the properties of bran sourdough. Copyright © 2013 Elsevier Ltd. All rights reserved.

Petrous apex cholesterol granuloma aeration: does it matter?

PubMed

Castillo, Michael P; Samy, Ravi N; Isaacson, Brandon; Roland, Peter S

2008-04-01

To determine whether aeration of surgically treated petrous apex cholesterol granulomas (PA CG) has any correlation with resolution of symptoms. Retrospective chart review. Twenty-six patients with a petrous apex cholesterol granuloma during a 16-year period were reviewed. Seventeen of 26 (65%) patients underwent surgical intervention. Preoperative symptoms included headache, facial weakness/twitching or numbness, vertigo, hearing loss, vision changes, and tinnitus. Postoperative symptoms resolved in 9 of the 16 patients (56%). Three patients had a postoperative headache. Facial nerve dysfunction persisted or recurred in four patients. One patient was lost to follow-up. Thirteen patients had postoperative imaging. All 13 (100%) patients demonstrated stable or increased size of PA CG with no evidence of aeration. Revision surgery was performed in four patients (25%) for facial nerve symptoms or persistent headaches. The extent of PA CG aeration on postoperative imaging had no correlation to symptom resolution or cyst enlargement. Revision surgery should not depend on imaging alone but primarily on patient symptoms and physical exam.

Pilot scale experiment with MBR operated in intermittent aeration condition: analysis of biological performance.

PubMed

Capodici, M; Di Bella, G; Di Trapani, D; Torregrossa, M

2015-02-01

The effect of intermittent aeration (IA) on a MBR system was investigated. The study was aimed at analyzing different working conditions and the influence of different IA cycles on the biological performance of the MBR pilot plant, in terms of organic carbon and ammonium removal as well as extracellular polymeric substances (EPSs) production. The membrane modules were placed in a separate compartment, continuously aerated. This configuration allowed to disconnect from the filtration stage the biological phenomena occurring into the IA bioreactor. The observed results highlighted good efficiencies, in terms of organic carbon and ammonium removal. It was noticed a significant soluble microbial products (SMPs) release, likely related to the higher metabolic stress that anoxic conditions exerted on the biomass. However, the proposed configuration, with the membranes in a separate compartment, allowed to reduce the EPSs in the membrane tank even during the non-aerated phase, thus lowering fouling development. Copyright © 2014 Elsevier Ltd. All rights reserved.

Aroma profiling of an aerated fermentation of natural grape must with selected yeast strains at pilot scale.

PubMed

Tronchoni, Jordi; Curiel, José Antonio; Sáenz-Navajas, María Pilar; Morales, Pilar; de-la-Fuente-Blanco, Arancha; Fernández-Zurbano, Purificación; Ferreira, Vicente; Gonzalez, Ramon

2018-04-01

The use of non-Saccharomyces strains in aerated conditions has proven effective for alcohol content reduction in wine during lab-scale fermentation. The process has been scaled up to 20 L batches, in order to produce lower alcohol wines amenable to sensory analysis. Sequential instead of simultaneous inoculation was chosen to prevent oxygen exposure of Saccharomyces cerevisiae during fermentation, since previous results indicated that this would result in increased acetic acid production. In addition, an adaptation step was included to facilitate non-Saccharomyces implantation in natural must. Wines elaborated with Torulaspora delbrueckii or Metschnikowia pulcherrima in aerated conditions contained less alcohol than control wine (S. cerevisiae, non-aerated). Sensory and aroma analysis revealed that the quality of mixed fermentations was affected by the high levels of some yeast amino acid related byproducts, which suggests that further progress requires a careful selection of non-Saccharomyces strains and the use of specific N-nutrients. Copyright © 2017 Elsevier Ltd. All rights reserved.

Computational fluid dynamics modelling of hydraulics and sedimentation in process reactors during aeration tank settling.

PubMed

Jensen, M D; Ingildsen, P; Rasmussen, M R; Laursen, J

2006-01-01

Aeration tank settling is a control method allowing settling in the process tank during high hydraulic load. The control method is patented. Aeration tank settling has been applied in several waste water treatment plants using the present design of the process tanks. Some process tank designs have shown to be more effective than others. To improve the design of less effective plants, computational fluid dynamics (CFD) modelling of hydraulics and sedimentation has been applied. This paper discusses the results at one particular plant experiencing problems with partly short-circuiting of the inlet and outlet causing a disruption of the sludge blanket at the outlet and thereby reducing the retention of sludge in the process tank. The model has allowed us to establish a clear picture of the problems arising at the plant during aeration tank settling. Secondly, several process tank design changes have been suggested and tested by means of computational fluid dynamics modelling. The most promising design changes have been found and reported.

Effect of aerated concrete blockwork joints on the heat transfer performance uniformity

NASA Astrophysics Data System (ADS)

Pukhkal, Viktor; Murgul, Vera

2018-03-01

Analysis of data on the effect of joints of the aerated concrete blocks on the heat transfer uniformity of exterior walls was carried out. It was concluded, that the values of the heat transfer performance uniformity factor in the literature sources were obtained for the regular fragment of a wall construction by approximate addition of thermal conductivities. Heat flow patterns for the aerated concrete exterior walls amid different values of the thermal conductivity factors and design ambient air temperature of -26 °C were calculated with the use of "ELCUT" software for modelling of thermal patterns by finite element method. There were defined the values for the heat transfer performance uniformity factor, reduced total thermal resistance and heat-flux density for the exterior walls. The calculated values of the heat transfer performance uniformity factors, as a function of the coefficient of thermal conductivity of aerated concrete blocks, differ from the known data by a more rigorous thermal and physical substantiation.

Recovery of ammonia from swine manure using gas-permeable membranes: effect of aeration.

PubMed

García-González, M C; Vanotti, M B; Szogi, A A

2015-04-01

The gas-permeable membrane process can recover ammonia from manure, reducing pollution whilst converting ammonia into an ammonium salt fertilizer. The process involves manure pH control to increase ammonium (NH4(+)) recovery rate that is normally carried out using an alkali. In this study a new strategy to avoid the use of alkali was tested applying low-rate aeration and nitrification inhibition. The wastewater used was raw swine manure with 2390 mg NH4(+)-N/L. Results showed that aeration increased pH above 8.5 allowing quick transformation of NH4(+) into gaseous ammonia (NH3) and efficient recovery by permeation through the submerged membrane. The overall NH4(+) recovery obtained with aeration was 98% and ammonia emissions losses were less than 1.5%. The new approach can substitute large amounts of alkali chemicals needed to obtain high NH4(+) recovery with important economic and environmental savings. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biotreatment of textile effluent in static bioreactor by Curvularia lunata URM 6179 and Phanerochaete chrysosporium URM 6181.

PubMed

Miranda, Rita de Cássia M de; Gomes, Edelvio de Barros; Pereira, Nei; Marin-Morales, Maria Aparecida; Machado, Katia Maria Gomes; Gusmão, Norma Buarque de

2013-08-01

Investigations on biodegradation of textile effluent by filamentous fungi strains Curvularia lunata URM 6179 and Phanerochaete chrysosporium URM 6181 were performed in static bioreactors under aerated and non-aerated conditions. Spectrophotometric, HPLC/UV and LC-MS/MS analysis were performed as for to confirm, respectively, decolourisation, biodegradation and identity of compounds in the effluent. Enzymatic assays revealed higher production of enzymes laccase (Lac), lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP) by P. chrysosporium URM 6181 in aerated bioreactor (2020; 39 and 392 U/l, respectively). Both strains decolourised completely the effluent after ten days and biodegradation of the most predominant indigo dye was superior in aerated bioreactor (96%). Effluent treated by P. chrysosporium URM 6181 accumulated a mutagenic metabolite derived from indigo. The C. lunata URM 6179 strain, showed to be more successful for assure the environmental quality of treated effluent. These systems were found very effective for efficient fungal treatment of textile effluent. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effective pine bark composting with the Dome Aeration Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trois, Cristina; Polster, Andreas

2007-07-01

In South Africa garden refuse is primarily disposed of in domestic landfills. Due to the large quantities generated, any form of treatment would be beneficial for volume reduction, waste stabilization and resource recovery. Dome Aeration Technology (DAT) is an advanced process for aerobic biological degradation of garden refuse and general waste [Paar, S., Brummack, J., Gemende, B., 1999a. Advantages of dome aeration in mechanical-biological waste treatment. In: Proceedings of the 7th International Waste Management and Landfill Symposium, Cagliari, 4-8 October 1999; Paar, S., Brummack, J., Gemende, B., 1999b. Mechanical-biological waste stabilization by the dome aeration method. Environment Protection Engineering 25more » (3/99). Mollekopf, N., Brummack, J., Paar, S., Vorster, K., 2002. Use of the Dome Aeration Technology for biochemical stabilization of waste prior to landfilling. In: Proceedings of the Wastecon 2002, Waste Congress and Exhibition, Durban, South Africa.]. It is a non-reactor open windrow composting process, with the main advantage being that the input material needs no periodic turning. A rotting time of only 3-4 months indicates the high efficiency. Additionally, the low capital/operational costs, low energy inputs and limited plant requirements provide potential for use in aerobic refuse stabilization. The innovation in the DAT process is the passive aeration achieved by thermally driven advection through open windrows caused by temperature differences between the degrading material and the outside environment. This paper investigates the application of Dome Aeration Technology to pine bark composting as part of an integrated waste management strategy. A full-scale field experiment was performed at the Bisasar Road Landfill Site in Durban to assess the influence of climate, waste composition and operational conditions on the process. A test windrow was constructed and measurements of temperature and airflow through the material were taken. The process monitoring revealed that prevailing climatic conditions in a subtropical location do not affect the high efficiency of this technology. However, the composition of the input material can be detrimental for production of high quality compost because of a lack of nitrate.« less

Pilot study on arsenic removal from groundwater using a small-scale reverse osmosis system-Towards sustainable drinking water production.

PubMed

Schmidt, Stefan-André; Gukelberger, Ephraim; Hermann, Mario; Fiedler, Florian; Großmann, Benjamin; Hoinkis, Jan; Ghosh, Ashok; Chatterjee, Debashis; Bundschuh, Jochen

2016-11-15

Arsenic contamination of groundwater is posing a serious challenge to drinking water supplies on a global scale. In India and Bangladesh, arsenic has caused the most serious public health issue in the world for nearly two decades. The aim of this work was to study an arsenic removal system based on reverse osmosis at pilot scale treating two different water sources from two different locations in the State of Bihar, India. For this purpose two villages, Bind Toli and Ramnagar in the Patna District were selected, both located very close to the river Ganga. The trials were conducted with aerated and non-aerated groundwater. It is the first time that the arsenic removal efficiency for aerated and non-aerated groundwater by reverse osmosis technology in combination with an energy-saving recovery system have been studied. As the principle of reverse osmosis requires a relatively high pressure, its energy demand is naturally high. By using an energy recovery system, this demand can be lowered, leading to an energy demand per liter permeate of 3-4Wh/L only. Due to high iron levels in the groundwater and as a consequence the precipitation of ferric (hydr)oxides, it was necessary to develop a granular media filter for the trials under aeration in order to protect the membrane from clogging. Two different materials, first locally available sand, and second commercially available anthracite were tested in the granular media filter. For the trials with aerated groundwater, total arsenic removal efficiency at both locations was around 99% and the arsenic concentration in permeate was in compliance with the WHO and National Indian Standard of 10μg/L. However, trials under anoxic conditions with non-aerated groundwater could not comply with this standard. Additionally a possible safe discharge of the reverse osmosis concentrate into an abandoned well was studied. It was observed that re-injection of reject water underground may offer a safe disposal option. However, long-term hydrogeological studies need to be conducted for confirmation. Copyright © 2016 Elsevier B.V. All rights reserved.

Estimated splash and training wall height requirements for stepped chutes applied to embankment dams

USDA-ARS?s Scientific Manuscript database

Aging embankment dams are commonly plagued with insufficient spillway capacity. To provide increased spillway capacity, stepped chutes are frequently applied as an overtopping protection system for embankment dams. Stepped chutes with sufficient length develops aerated flow. The aeration and flow...

OFF-GAS ANALYSIS RESULTS AND FINE PORE RETROFIT INFORMATION FOR GLASTONBURY, CONNECTICUT

EPA Science Inventory

In the summer of 1984, the Glastonbury, Connecticut Water Pollution Control Plant underwent a retrofit from a spiral roll coarse bubble to a spiral roll fine pore aeration system. Only diffuser replacement was performed in the aeration tanks. From November 1985 through Septembe...

Evaluation of ammonia emissions from manure incorporated with different soil aerator configurations

USDA-ARS?s Scientific Manuscript database

The incorporation of swine manure with tillage effectively reduces ammonia emissions and conserves crop available N but is not compatible with no-till and many other conservation tillage programs. Rolling-tine aerators potentially provide a means to enhance manure infiltration with limited disruptio...

EVALUATING THE COSTS OF PACKED-TOWER AERATION AND GAC FOR CONTROLLING SELECTED ORGANICS

EPA Science Inventory

This article focuses on a preliminary cost analysis that compares liquid-phase granular activated carbon (GAC) treatment with packed-tower aeration (PTA) treatment, with and without air emissions control. The sensitivity of cost to design and operating variables is also discussed...

CASE HISTORY OF FINE PORE DIFFUSER RETROFIT AT RIDGEWOOD, NEW JERSEY

EPA Science Inventory

In April 1983, the Ridgewood, New Jersey Wastewater Treatment Plant underwent a retrofit from a coarse bubble to a fine pore aeration system. Also, process modification from contact stabilization to tapered aeration occurred. This report presents a case history of plant and aer...

Field study of nitrous oxide production with in situ aeration in a closed landfill site.

PubMed

Nag, Mitali; Shimaoka, Takayuki; Nakayama, Hirofumi; Komiya, Teppei; Xiaoli, Chai

2016-03-01

Nitrous oxide (N(2)O) has gained considerable attention as a contributor to global warming and depilation of stratospheric ozone layer. Landfill is one of the high emitters of greenhouse gas such as methane and N(2)O during the biodegradation of solid waste. Landfill aeration has been attracted increasing attention worldwide for fast, controlled and sustainable conversion of landfills into a biological stabilized condition, however landfill aeration impel N(2)O emission with ammonia removal. N(2)O originates from the biodegradation, or the combustion of nitrogen-containing solid waste during the microbial process of nitrification and denitrification. During these two processes, formation of N(2)O as a by-product from nitrification, or as an intermediate product of denitrification. In this study, air was injected into a closed landfill site and investigated the major N(2)O production factors and correlations established between them. The in-situ aeration experiment was carried out by three sets of gas collection pipes along with temperature probes were installed at three different distances of one, two and three meter away from the aeration point; named points A-C, respectively. Each set of pipes consisted of three different pipes at three different depths of 0.0, 0.75 and 1.5 m from the bottom of the cover soil. Landfill gases composition was monitored weekly and gas samples were collected for analysis of nitrous oxide concentrations. It was evaluated that temperatures within the range of 30-40°C with high oxygen content led to higher generation of nitrous oxide with high aeration rate. Lower O(2) content can infuse N(2)O production during nitrification and high O(2) inhibit denitrification which would affect N(2)O production. The findings provide insights concerning the production potentials of N(2)O in an aerated landfill that may help to minimize with appropriate control of the operational parameters and biological reactions of N turnover. Investigation of nitrous oxide production potential during in situ aeration in an old landfill site revealed that increased temperatures and oxygen content inside the landfill site are potential factors for nitrous oxide production. Temperatures within the range of optimum nitrification process (30-40°C) induce nitrous oxide formation with high oxygen concentration as a by-product of nitrogen turnover. Decrease of oxygen content during nitrification leads increase of nitrous oxide production, while temperatures above 40°C with moderate and/or low oxygen content inhibit nitrous oxide generation.

Incorporation of air into a snack food reduces energy intake

PubMed Central

Osterholt, Kathrin M.; Roe, Liane S.

2007-01-01

This study investigated how the air content of a familiar snack food affected energy intake and whether varying the method of serving the snack modified intake. We tested two versions of an extruded snack (cheese puffs) that were equal in energy density (5.7 kcal/g), but differed in energy per volume (less-aerated snack: 1.00 kcal/ml; more- aerated snack: 0.45 kcal/ml). In a within-subjects design, 16 women and 12 men consumed the snacks ad libitum in the laboratory during four afternoon sessions. A standard volume (1250 ml) of each snack was served once in a bowl and once in an opaque bag. Results showed that intake of the two snacks differed significantly by energy (p=0.0003) and volume (p<0.0001); subjects consumed 21% less weight and energy (70±17 kcal) of the more-aerated snack than the less-aerated snack, although they consumed a 73% greater volume of the more-aerated snack (239±24 ml). These findings suggest that subjects responded to both the weight and volume of the snack. Despite differences in intake, hunger and fullness ratings did not differ across conditions. The serving method did not significantly affect intake. Results from this study indicate that incorporating air into food provides a strategy to reduce energy intake from energy-dense snacks. PMID:17188782

Minimizing N2O emissions and carbon footprint on a full-scale activated sludge sequencing batch reactor.

PubMed

Rodriguez-Caballero, A; Aymerich, I; Marques, Ricardo; Poch, M; Pijuan, M

2015-03-15

A continuous, on-line quantification of the nitrous oxide (N2O) emissions from a full-scale sequencing batch reactor (SBR) placed in a municipal wastewater treatment plant (WWTP) was performed in this study. In general, N2O emissions from the biological wastewater treatment system were 97.1 ± 6.9 g N2O-N/Kg [Formula: see text] consumed or 6.8% of the influent [Formula: see text] load. In the WWTP of this study, N2O emissions accounted for over 60% of the total carbon footprint of the facility, on average. Different cycle configurations were implemented in the SBR aiming at reaching acceptable effluent values. Each cycle configuration consisted of sequences of aerated and non-aerated phases of different time length being controlled by the ammonium set-point fixed. Cycles with long aerated phases showed the largest N2O emissions, with the consequent increase in carbon footprint. Cycle configurations with intermittent aeration (aerated phases up to 20-30 min followed by short anoxic phases) were proven to effectively reduce N2O emissions, without compromising nitrification performance or increasing electricity consumption. This is the first study in which a successful operational strategy for N2O mitigation is identified at full-scale. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of the aerated structure on selected properties of freeze-dried hydrocolloid gels

NASA Astrophysics Data System (ADS)

Ciurzyńska, Agnieszka; Lenart, Andrzej

2016-01-01

The ability to create diverse structures and studies on the effect of the aerated structure on selected properties with the use of freeze-dried gels may provide knowledge about the properties of dried foods. Such gels can be a basis for obtaining innovative food products. For the gel preparation, 3 types of hydrocolloids were used: low-methoxyl pectin, a mixture of xanthan gum and locust-bean gum, and a mixture of xanthan gum and guar gum. Gels were aerated for 3 and 7 min, frozen at a temperature of -45°C 2 h-1, and freeze-dried at a temperature of 30°C. For the samples obtained, structure, porosity, shrinkage, rehydration, and colour were investigated. It was shown that the type of the hydrocolloid and aeration time influence the structure of freeze-dried gels, which determines such properties of samples as porosity, shrinkage, density, rehydration, and colour. The bigger pores of low-methoxyl pectin gels undergo rehydration in the highest degree. The delicate and aerated structure of gels with the mixture of xanthan gum and locust-bean gum was damaged during freeze-drying and shrinkage exhibited the highest value. Small pores of samples with the mixture of xanthan gum and guar gum were responsible for the lower rehydration properties, but the highest porosity value contributed to the highest lightness value.

Non-autoclaved aerated concrete with mineral additives

NASA Astrophysics Data System (ADS)

Il'ina, L. V.; Rakov, M. A.

2016-01-01

We investigated the effect of joint grinding of Portland cement clinker, silica and carbonate components and mineral additives to specific surface of 280 - 300 m2/kg on the properties (strength, average density and thermal conductivity) of non-autoclaved aerated concrete, and the porosity of the hardened cement paste produced from Portland cement clinker with mineral additives. The joint grinding of the Portland cement clinker with silica and carbonate components and mineral additives reduces the energy consumption of non-autoclaved aerated concrete production. The efficiency of mineral additives (diopside, wollastonite) is due to the closeness the composition, the type of chemical bonds, physical and chemical characteristics (specific enthalpy of formation, specific entropy) to anhydrous clinker minerals and their hydration products. Considering the influence of these additions on hydration of clinker minerals and formation of hardened cement paste structure, dispersed wollastonite and diopside should be used as mineral additives. The hardness and, consequently, the elastic modulus of diopside are higher than that of hardened cement paste. As a result, there is a redistribution of stresses in the hardened cement paste interporous partitions and hardening, both the partitions and aerated concrete on the whole. The mineral additives introduction allowed to obtain the non-autoclaved aerated concrete with average density 580 kg/m3, compressive strength of 3.3 MPa and thermal conductivity of 0.131 W/(m.°C).

Nitrogen removal on recycling water process of wastewater treatment plant effluent using subsurface horizontal wetland with continuous feed

NASA Astrophysics Data System (ADS)

Tazkiaturrizki, T.; Soewondo, P.; Handajani, M.

2018-01-01

Recycling water is a generic term for water reclamation and reuse to solve the scarcity of water. Constructed wetlands have been recognized as providing many benefits for wastewater treatment including water supply and control by recycling water. This research aims to find the best condition to significantly remove nitrogen using constructed wetland for recycling water of Bojongsoang Waste Water Treatment Plan (WWTP) effluent. Using media of soil, sand, gravel, and vegetation (Typha latifolia and Scirpus grossus) with an aeration system, BOD and COD parameters have been remarkably reduced. On the contrary, the removal efficiency for nitrogen is only between 50-60%. Modifications were then conducted by three step of treatment, i.e., Step I is to remove BOD/COD using Typha latifolia with an aeration system, Step II is todecrease nitrogen using Scirpus grossus with/without aeration, and Step III isto complete the nitrogen removal with denitrification process by Glycine max without aeration. Results of the research show that the nitrogen removal has been successfully increased to a high efficiency between 80-99%. The combination of aeration system and vegetation greatly affects the nitrogen removal. The vegetation acts as the organic nitrogen consumer (plant uptake) for amino acids, nitrate, and ammonium as nutrition, as well as theoxygen supplier to the roots so that aerobic microsites are formed for ammonification microorganisms.

Do radial oxygen loss and external aeration affect iron plaque formation and arsenic accumulation and speciation in rice?

PubMed Central

Wu, Chuan; Ye, Zhihong; Li, Hui; Wu, Shengchun; Deng, Dan; Zhu, Yongguan; Wong, Minghung

2012-01-01

Hydroponic experiments were conducted to investigate the effect of radial oxygen loss (ROL) and external aeration on iron (Fe) plaque formation, and arsenic (As) accumulation and speciation in rice (Oryza sativa L.). The data showed that there were significant correlations between ROL and Fe concentrations in Fe plaque produced on different genotypes of rice. There were also significant differences in the amounts of Fe plaque formed between different genotypes in different positions of roots and under different aeration conditions (aerated, normal, and stagnant treatments). In aerated treatments, rice tended to have a higher Fe plaque formation than in a stagnant solution, with the greatest formation at the root tip decreasing with increasing distances away, in accordance with a trend of spatial ROL. Genotypes with higher rates of ROL induced higher degrees of Fe plaque formation. Plaques sequestered As on rice roots, with arsenate almost double that with arsenite, leading to decreased As accumulation in both roots and shoots. The major As species detected in roots and shoots was arsenite, ranging from 34 to 78% of the total As in the different treatments and genotypes. These results contribute to our understanding of genotypic differences in As uptake by rice and the mechanisms causing rice genotypes with higher ROL to show lower overall As accumulation. PMID:22345639

Pollutants' Release, Redistribution and Remediation of Black Smelly River Sediment Based on Re-Suspension and Deep Aeration of Sediment.

PubMed

Zhu, Lin; Li, Xun; Zhang, Chen; Duan, Zengqiang

2017-04-01

Heavily polluted sediment is becoming an important part of water pollution, and this situation is particularly acute in developing countries. Sediment has gradually changed from being the pollution adsorbent to the release source and has influenced the water environment and public health. In this study, we evaluated the pollutant distribution in sediment in a heavily polluted river and agitated the sediment in a heavily polluted river to re-suspend it and re-release pollutants. We found that the levels of chemical oxygen demand (COD), NH₄⁺-N, total nitrogen (TN), and total phosphorus (TP) in overlying water were significantly increased 60 min after agitation. The distribution of the pollutants in the sediment present high concentrations of pollutants congregated on top of the sediment after re-settling, and their distribution decreased with depth. Before agitation, the pollutants were randomly distributed throughout the sediment. Secondly, deep sediment aeration equipment (a micro-porous air diffuser) was installed during the process of sedimentation to study the remediation of the sediment by continuous aeration. The results revealed that deep sediment aeration after re-suspension significantly promoted the degradation of the pollutants both in overlying water and sediment, which also reduced the thickness of the sediment from 0.9 m to 0.6 m. Therefore, sediment aeration after suspension was efficient, and is a promising method for sediment remediation applications.

Low-concentration tailing and subsequent quicklime-enhanced remediation of volatile chlorinated hydrocarbon-contaminated soils by mechanical soil aeration.

PubMed

Ma, Yan; Du, Xiaoming; Shi, Yi; Xu, Zhu; Fang, Jidun; Li, Zheng; Li, Fasheng

2015-02-01

Mechanical soil aeration has long been regarded as an effective ex-situ remediation technique and as suitable for remediation of large-scale sites contaminated by volatile organic compounds (VOCs) at low cost. However, it has been reported that the removal efficiency of VOCs from soil is relatively low in the late stages of remediation, in association with tailing. Tailing may extend the remediation time required; moreover, it typically results in the presence of contaminants residues at levels far exceeding regulations. In this context, the present study aimed to discuss the tailing that occurs during the process of remediation of soils contaminated artificially with volatile chlorinated hydrocarbons (VCHs) and to assess possible quicklime-enhanced removal mechanisms. The results revealed the following conclusions. First, temperature and aeration rate can be important controls on both the timing of appearance of tailing and the levels of residual contaminants. Furthermore, the addition of quicklime to soil during tailing can reduce the residual concentrations rapidly to below the remedial target values required for site remediation. Finally, mechanical soil aeration can be enhanced using quicklime, which can improve the volatilization of VCHs via increasing soil temperature, reducing soil moisture, and enhancing soil permeability. Our findings give a basic understanding to the elimination of the tailing in the application of mechanical soil aeration, particularly for VOCs-contaminated soils. Copyright © 2014 Elsevier Ltd. All rights reserved.

Laboratory- and full-scale studies on the removal of pharmaceuticals in an aerated constructed wetland: effects of aeration and hydraulic retention time on the removal efficiency and assessment of the aquatic risk.

PubMed

Auvinen, Hannele; Gebhardt, Wilhelm; Linnemann, Volker; Du Laing, Gijs; Rousseau, Diederik P L

2017-09-01

Pharmaceutical residues in wastewater pose a challenge to wastewater treatment technologies. Constructed wetlands (CWs) are common wastewater treatment systems in rural areas and they discharge often in small water courses in which the ecology can be adversely affected by the discharged pharmaceuticals. Hence, there is a need for studies aiming to improve the removal of pharmaceuticals in CWs. In this study, the performance of a full-scale aerated sub-surface flow hybrid CW treating wastewater from a healthcare facility was studied in terms of common water parameters and pharmaceutical removal. In addition, a preliminary aquatic risk assessment based on hazard quotients was performed to estimate the likelihood of adverse effects on aquatic organisms in the forest creek where this CW discharges. The (combined) effect of aeration and hydraulic retention time (HRT) was evaluated in a laboratory-scale batch experiment. Excellent removal of the targeted pharmaceuticals was obtained in the full-scale CW (>90%) and, as a result, the aquatic risk was estimated low. The removal efficiency of only a few of the targeted pharmaceuticals was found to be dependent on the applied aeration (namely gabapentin, metformin and sotalol). Longer and the HRT increased the removal of carbamazepine, diclofenac and tramadol.

Recovery of ammonia and production of high-grade phosphates from digester effluents (municipal and livestock)

USDA-ARS?s Scientific Manuscript database

Phosphorus (P) recovery of anaerobically digested swine wastewater and side-stream municipal wastewater via magnesium precipitation was enhanced by combining it with the recovery of ammonia (NH3) through gas-permeable membranes and low-rate aeration. The low-rate aeration stripped the natural carbon...

DEMONSTRATION BULLETIN: LOW TEMPERATURE THERMAL AERATION (LTTA®) SYSTEM - CANONIE ENVIRONMENTAL SERVICES, INC.

EPA Science Inventory

The Low Temperature Thermal Aeration (LTTA®) process was developed by Canonie Environmental Services, Inc. (Canonie), as a treatment system that desorbs organic contaminants from soils by heating the soils up to 800 °F. The main components of the LTTA process include the follow...

Pilot Plant Demonstration of Stable and Efficient High Rate Biological Nutrient Removal with Low Dissolved Oxygen Conditions

EPA Science Inventory

Aeration in biological nutrient removal (BNR) processes accounts for nearly half of the total electricity costs at many wastewater treatment plants. Even though conventional BNR processes are usually operated to have aerated zones with high dissolved oxygen (DO) concentrations, r...

Processes to improve energy efficiency during pumping and aeration of recirculating water in circular tank systems

USDA-ARS?s Scientific Manuscript database

Conventional gas transfer technologies for aquaculture systems occupy a large amount of space, require considerable capital investment, and can contribute to high electricity demand. In addition, diffused aeration in a circular tank can interfere with the hydrodynamics of water rotation and the spee...

Activated Sludge. Student Manual. Biological Treatment Process Control.

ERIC Educational Resources Information Center

Boe, Owen K.; Klopping, Paul H.

This student manual contains the textual material for a seven-lesson unit on activated sludge. Topic areas addressed in the lessons include: (1) activated sludge concepts and components (including aeration tanks, aeration systems, clarifiers, and sludge pumping systems); (2) activated sludge variations and modes; (3) biological nature of activated…

Improvement of anaerobic digester performance by wastewater recirculation through an aerated membrane.

USDA-ARS?s Scientific Manuscript database

Swine wastewater from an anaerobic digester was recirculated through a silicone hose located in an external aeration chamber to determine its effect on wastewater malodorants and biogas composition. The silicone hose acted as a semipermeable membrane for the passage of small molecules. In the first...

Evaluation of cost-effective aeration technology solutions to address total trihalomethane (TTHM) compliance

EPA Science Inventory

The primary objective of this project was to evaluate cost-effective aeration technology solutions to address TTHM compliance at a water treatment plant clearwell. The project team worked closely with EPA Region 6 and the EPA Office of Research and Development (ORD) to identify a...

Retrofitting activated sludge systems to intermittent aeration for nitrogen removal.

PubMed

Hanhan, O; Artan, N; Orhon, D

2002-01-01

The paper provides the basis and the conceptual approach of applying process kinetics and modelling to the design of alternating activated sludge systems for retrofitting existing activated sludge plants to intermittent aeration for nitrogen removal. It shows the significant role of the two specific parameters, namely, the aerated fraction and the cycle time ratio on process performance through model simulations and proposes a way to incorporate them into a design procedure using process stoichiometry and mass balance. It illustrates the effect of these parameters, together with the sludge age, in establishing the balance between the denitrification potential and the available nitrogen created in the anoxic/aerobic sequences of system operation.

Disposable rabbit

DOEpatents

Lewis, Leroy C.; Trammell, David R.

1986-01-01

A disposable rabbit for transferring radioactive samples in a pneumatic transfer system comprises aerated plastic shaped in such a manner as to hold a radioactive sample and aerated such that dissolution of the rabbit in a solvent followed by evaporation of the solid yields solid waste material having a volume significantly smaller than the original volume of the rabbit.

Disposal rabbit

DOEpatents

Lewis, L.C.; Trammell, D.R.

1983-10-12

A disposable rabbit for transferring radioactive samples in a pneumatic transfer system comprises aerated plastic shaped in such a manner as to hold a radioactive sample and aerated such that dissolution of the rabbit in a solvent followed by evaporation of the solid yields solid waste material having a volume significantly smaller than the original volume of the rabbit.

Influence of liquid surface area on hydrogen sulfide oxidation during micro-aeration in dairy manure digesters

USDA-ARS?s Scientific Manuscript database

The specific objectives of this study were to evaluate headspace aeration for reducing hydrogen sulfide levels in low cost plug flow digesters, and to characterize the relationship between the liquid surface area and hydrogen sulfide oxidation rates. Experiments with replicate field scale plug flow ...

Framework for Energy Neutral Treatment for the 21st Century Through Energy Efficient Aeration (WERF Report INFR2R12)

EPA Science Inventory

Aeration is commonly identified as the most significant energy use in the treatment of wastewater and therefore garners significant focus in reducing energy use in the ultimate aspirational goal of achieving net energy neutrality for water resource recovery. This research establi...

Reducing Volatile Disinfection By-Products in Treated Drinking Water Using Aeration Technologies (WaterRF Report 4441)

EPA Science Inventory

The primary objective of this project was to evaluate cost-effective aeration technology solutions to address TTHM compliance at a water treatment plant clearwell. The project team worked closely with EPA Region 6 and the EPA Office of Research and Development (ORD) to identify a...

Development and on-site field testing of the power-tube airlift aerator and chances for commercialization

USDA-ARS?s Scientific Manuscript database

Aeration of ponds when dissolved oxygen (DO) concentrations are low is the principal management tool that allows for higher feeding rates, increased production, and decreased cost per unit fish produced. Recent research conducted at the USDA-ARS Warmwater Aquaculture Research Unit has shown that fee...

Application of mathematical model methods for optimization tasks in construction materials technology

NASA Astrophysics Data System (ADS)

Fomina, E. V.; Kozhukhova, N. I.; Sverguzova, S. V.; Fomin, A. E.

2018-05-01

In this paper, the regression equations method for design of construction material was studied. Regression and polynomial equations representing the correlation between the studied parameters were proposed. The logic design and software interface of the regression equations method focused on parameter optimization to provide the energy saving effect at the stage of autoclave aerated concrete design considering the replacement of traditionally used quartz sand by coal mining by-product such as argillite. The mathematical model represented by a quadric polynomial for the design of experiment was obtained using calculated and experimental data. This allowed the estimation of relationship between the composition and final properties of the aerated concrete. The surface response graphically presented in a nomogram allowed the estimation of concrete properties in response to variation of composition within the x-space. The optimal range of argillite content was obtained leading to a reduction of raw materials demand, development of target plastic strength of aerated concrete as well as a reduction of curing time before autoclave treatment. Generally, this method allows the design of autoclave aerated concrete with required performance without additional resource and time costs.

Effect of dissolved oxygen on heterotrophic denitrification using poly(butylene succinate) as the carbon source and biofilm carrier.

PubMed

Luo, Guozhi; Li, Li; Liu, Qian; Xu, Guimei; Tan, Hongxin

2014-11-01

The effect of dissolved oxygen (DO) on heterotrophic denitrification using poly(butylene succinate) as the carbon source and biofilm carrier was evaluated in a lab-scale experiment. Aerated, low-oxygen, and anoxic treatment groups were set up, which had average DO concentrations of 5.2±1.0, 1.4±1.2, and 0.5±0.3 mg L(-1), respectively. The NO3(-)-N and total nitrogen (TN) removal rates in the aerated group (37.44±0.24 and 36.24±0.48 g m(-3) d(-1), respectively) were higher than those in the other two groups. There was no significant difference between the low-oxygen and anoxic groups for the NO3(-)-N or TN removal rate. Accumulation of NO2(-)-N reached 5.0 mg L(-1) in the aerated group; no nitrite accumulation was found in the other two treatment groups. Bacterial communities of the low-oxygen and anoxic groups showed high similarity and were significantly different from those of the aerated group. Copyright © 2014 Elsevier Ltd. All rights reserved.

Optimization of submerged depth of surface aerators for a carrousel oxidation ditch based on large eddy simulation with Smagorinsky model.

PubMed

Wei, Wenli; Bai, Yu; Liu, Yuling

2016-01-01

This paper is concerned with the simulation and experimental study of hydraulic characteristics in a pilot Carrousel oxidation ditch for the optimization of submerged depth ratio of surface aerators. The simulation was based on the large eddy simulation with the Smagorinsky model, and the velocity was monitored in the ditches with an acoustic Doppler velocimeter method. Comparisons of the simulated velocities and experimental ones show a good agreement, which validates that the accuracy of this simulation is good. The best submerged depth ratio of 2/3 for surface aerators was obtained according to the analysis of the flow field structure, the ratio of gas and liquid in the bottom layer of a ditch, the average velocity of mixture and the flow region with a velocity easily causing sludge deposition under the four operation conditions with submerged depth ratios of 1/3, 1/2, 2/3 and 3/4 for surface aerators. The research result can provide a reference for the design of Carrousel oxidation ditches.

Bubble growth as a means to measure dissolved nitrogen concentration in aerated water

NASA Astrophysics Data System (ADS)

Ando, Keita; Yamashita, Tatsuya

2017-11-01

Controlling the amount of dissolved gases in water is important, for example, to food processing; it is essential to quantitatively evaluate dissolved gas concentration. The concentration of dissolved oxygen (DO) can be measured by commercial DO meters, but that of dissolved nitrogen (DN) cannot be obtained easily. Here, we propose a means to measure DN concentration based on Epstein-Plesset-type analysis of bubble growth under dissolved gas supersaturation. DO supersaturation in water is produced by oxygen microbubble aeration. The diffusion-driven growth of bubbles nucleated at glass surfaces in contact with the aerated water is first observed. The observed growth is then compared to the extended Epstein-Plesset theory that considers Fick's mass transfer of both DO and DN across bubble interfaces; in this comparison, the unknown DN concentration is treated as a fitting parameter. Comparisons between the experiment and the theory suggest, as expected, that DN can be effectively purged by oxygen microbubble aeration. This study was supported in part by the Mizuho Foundation for the Promotion of Science and by a MEXT Grant-in-Aid for the Program for Leading Graduate Schools.

Comparison of Biomass and Lipid Production under Ambient Carbon Dioxide Vigorous Aeration and 3% Carbon Dioxide Condition Among the Lead Candidate Chlorella Strains Screened by Various Photobioreactor Scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Naoko; Barnes, Austin; Jensen, Travis

2015-09-01

Chlorella species from the UTEX collection, classified by rDNA-based phylogenetic analysis, were screened based on biomass and lipid production in different scales and modes of culture. Lead candidate strains of C. sorokiniana UTEX 1230 and C. vulgaris UTEX 395 and 259 were compared between conditions of vigorous aeration with filtered atmospheric air and 3% CO 2 shake-flask cultivation. We found that the biomass of UTEX 1230 produced 2 times higher at 652 mg L -1 dry weight under both ambient CO 2 vigorous aeration and 3% CO 2 conditions, while UTEX 395 and 259 under 3% CO 2 increased tomore » 3 times higher at 863 mg L -1 dry weight than ambient CO 2 vigorous aeration. The triacylglycerol contents of UTEX 395 and 259 increased more than 30 times to 30% dry weight with 3% CO 2, indicating that additional CO 2 is essential for both biomass and lipid accumulation in UTEX 395 and 259.« less

[Co-composting high moisture vegetable waste and flower waste in a sequential fed operation].

PubMed

Zhang, Xiangfeng; Wang, Hongtao; Nie, Yongfeng

2003-11-01

Co-composting of high moisture vegetable wastes (celery and cabbage) and flower wastes (carnation) were studied in a sequential fed bed. The preliminary materials of composting were celery and carnation wastes. The sequential fed materials of composting were cabbage wastes and were fed every 4 days. Moisture content of mixture materials was between 60% and 70%. Composting was done in an aerobic static bed of composting based temperature feedback and control via aeration rate regulation. Aeration was ended when temperature of the pile was about 40 degrees C. Changes of composting of temperature, aeration rate, water content, organic matter, ash, pH, volume, NH4(+)-N, and NO3(-)-N were studied. Results show that co-composting of high moisture vegetable wastes and flower wastes, in a sequential fed aerobic static bed based temperature feedback and control via aeration rate regulation, can stabilize organic matter and removal water rapidly. The sequential fed operation are effective to overcome the difficult which traditional composting cannot applied successfully where high moisture vegetable wastes in more excess of flower wastes, such as Dianchi coastal.

Diurnal variations of the energy intensity and associated greenhouse gas emissions for activated sludge processes.

PubMed

Emami, Nasir; Sobhani, Reza; Rosso, Diego

2018-04-01

A model was developed for a water resources recovery facility (WRRF) activated sludge process (ASP) in Modified Ludzack-Ettinger (MLE) configuration. Amplification of air requirements and its associated energy consumptions were observed as a result of concurrent circadian variations in ASP influent flow and carbonaceous/nitrogenous constituent concentrations. The indirect carbon emissions associated with the ASP aeration were further amplified due to the simultaneous variations in carbon emissions intensity (kgCO 2,eq (kWh) -1 ) and electricity consumption (kWh). The ratio of peak to minimum increased to 3.4 (for flow), 4.2 (for air flow and energy consumption), and 5.2 (for indirect CO 2,eq emission), which is indicative of strong amplification. Similarly, the energy costs for ASP aeration were further increased due to the concurrency of peak energy consumptions and power demands with time of use peak electricity rates. A comparison between the results of the equilibrium model and observed data from the benchmark WRRF demonstrated under- and over-aeration attributed to the circadian variation in air requirements and limitations associated with the aeration system specification and design.

Mechanism and design of intermittent aeration activated sludge process for nitrogen removal.

PubMed

Hanhan, Oytun; Insel, Güçlü; Yagci, Nevin Ozgur; Artan, Nazik; Orhon, Derin

2011-01-01

The paper provided a comprehensive evaluation of the mechanism and design of intermittent aeration activated sludge process for nitrogen removal. Based on the specific character of the process the total cycle time, (T(C)), the aerated fraction, (AF), and the cycle time ratio, (CTR) were defined as major design parameters, aside from the sludge age of the system. Their impact on system performance was evaluated by means of process simulation. A rational design procedure was developed on the basis of basic stochiometry and mass balance related to the oxidation and removal of nitrogen under aerobic and anoxic conditions, which enabled selected of operation parameters of optimum performance. The simulation results indicated that the total nitrogen level could be reduced to a minimum level by appropriate manipulation of the aerated fraction and cycle time ratio. They also showed that the effluent total nitrogen could be lowered to around 4.0 mgN/L by adjusting the dissolved oxygen set-point to 0.5 mg/L, a level which promotes simultaneous nitrification and denitrification.

Production of L-lactic acid by a thermophilic Bacillus mutant using sodium hydroxide as neutralizing agent.

PubMed

Qin, Jiayang; Wang, Xiuwen; Zheng, Zhaojuan; Ma, Cuiqing; Tang, Hongzhi; Xu, Ping

2010-10-01

A sodium lactate tolerant mutant strain named Bacillus sp. Na-2 was obtained and applied to sodium hydroxide-based L-lactic acid (LA) production process. The influences of aeration and pH were investigated to further improve the resistance of strain Na-2 against sodium lactate stress and to obtain the most efficient L-LA production process. Although mild aeration was favorable for cell growth and L-LA production, vigorous aeration resulted in a metabolic shift from homolactic to mixed-acid/acetoin fermentation. Therefore, a two-stage aeration control strategy was employed. Optimum pH was found to be 6.0. A total of 106.0 g/l L-LA was produced in 30 h by Bacillus sp. Na-2 using sodium hydroxide as neutralizing agent. Productivity, conversion rate and optical purity were 3.53 g/l/h, 94% and 99.5%, respectively. The remarkable fermentation traits of Bacillus sp. Na-2 and the environment-friendly characteristics of NaOH-based process represent new insight for industrial scale production of L-LA. Copyright 2010 Elsevier Ltd. All rights reserved.

Effects of aeration and internal recycle flow on nitrous oxide emissions from a modified Ludzak-Ettinger process fed with glycerol.

PubMed

Song, Kang; Suenaga, Toshikazu; Harper, Willie F; Hori, Tomoyuki; Riya, Shohei; Hosomi, Masaaki; Terada, Akihiko

2015-12-01

Nitrous oxide (N2O) is emitted from a modified Ludzak-Ettinger (MLE) process, as a primary activated sludge system, which requires mitigation. The effects of aeration rates and internal recycle flow (IRF) ratios on N2O emission were investigated in an MLE process fed with glycerol. Reducing the aeration rate from 1.5 to 0.5 L/min increased gaseous the N2O concentration from the aerobic tank and the dissolved N2O concentration in the anoxic tank by 54.4 and 53.4 %, respectively. During the period of higher aeration, the N2O-N conversion ratio was 0.9 % and the potential N2O reducers were predominantly Rhodobacter, which accounted for 21.8 % of the total population. Increasing the IRF ratio from 3.6 to 7.2 decreased the N2O emission rate from the aerobic tank and the dissolved N2O concentration in the anoxic tank by 56 and 48 %, respectively. This study suggests effective N2O mitigation strategies for MLE systems.

Optimization of the nitrification process of wastewater resulting from cassava starch production.

PubMed

Fleck, Leandro; Ferreira Tavares, Maria Hermínia; Eyng, Eduardo; Orssatto, Fabio

2018-05-14

The present study has the objective of optimizing operational conditions of an aerated reactor applied to the removal of ammoniacal nitrogen from wastewater resulting from the production of cassava starch. An aerated reactor with a usable volume of 4 L and aeration control by rotameter was used. The airflow and cycle time parameters were controlled and their effects on the removal of ammoniacal nitrogen and the conversion to nitrate were evaluated. The highest ammoniacal nitrogen removal, of 96.62%, occurred under conditions of 24 h and 0.15 L min -1 L reactor -1 . The highest nitrate conversion, of 24.81%, occurred under conditions of 40.92 h and 0.15 L min -1  L reactor -1 . The remaining value of ammoniacal nitrogen was converted primarily into nitrite, energy, hydrogen and water. The optimal operational values of the aerated reactor are 29.25 h and 0.22 L min -1  L reactor -1 . The mathematical models representative of the process satisfactorily describe ammoniacal nitrogen removal efficiency and nitrate conversion, presenting errors of 2.87% and 3.70%, respectively.

Investigation of transient forms of sulfur during biological treatment of spent caustic.

PubMed

Kalantari, Hamed; Nosrati, Mohsen; Shojaosadati, Seyed Abbas; Shavandi, Mahmoud

2018-06-01

In the present study, the production of various transient forms of sulfur during biological oxidation of sulfidic spent caustics under haloalkaline conditions in a stirred tank bioreactor is investigated. Also, the effects of abiotic aeration (chemical oxidation), dissolved oxygen (DO) concentration and sodium concentration on forms of sulfur during biological treatment are demonstrated. Thioalkalivibrio versutus strain was used for sulfide oxidation in spent caustic (SC). The aeration had an important effect on sulfide oxidation and its final products. At DO concentrations above 2 mg l -1 , majority of sulfide was oxidized to sulfate. Maximum sulfide removal efficiency (%R) and yield of sulfate production [Formula: see text] was obtained in Na + concentration ranging from 0.6 to 2 M. Abiotic aeration, which is the most important factor of production of thiosulfate, resulted in the formation of an undesired product-polysulfide. However, abiotic aeration can be used as a pretreatment to biological treatment. In the bioreactor the removal efficiency was obtained as 82.7% and various forms of sulfur such as polysulfide, biosulfur, thiosulfate and sulfate was observed during biological treatment of SC.

Multiple electron transfer systems in oxygen reducing biocathodes revealed by different conditions of aeration/agitation.

PubMed

Rimboud, Mickaël; Bergel, Alain; Erable, Benjamin

2016-08-01

Oxygen reducing biocathodes were formed at -0.2V/SCE (+0.04V/SHE) from compost leachate. Depending on whether aeration was implemented or not, two different redox systems responsible for the electrocatalysis of oxygen reduction were evidenced. System I was observed at low potential (-0.03V/SHE) on cyclic voltammetries (CVs). It appeared during the early formation of the biocathode (few hours) and resisted the hydrodynamic conditions induced by the aeration. System II was observed at higher potential on CV (+0.46V/SHE); it required a longer lag time (up to 10days) and quiescent conditions to produce an electrochemical signal. The hydrodynamic effects produced by the forced aeration led to its extinction. From their different behaviors and examples in the literature, system I was identified as being a membrane-bound cytochrome-related molecule, while system II was identified as a soluble redox mediator excreted by the biofilm. This study highlighted the importance of controlling the local hydrodynamics to design efficient oxygen reducing biocathodes able to operate at high potential. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of hydraulic loading rate on pollutant removal efficiency in subsurface infiltration system under intermittent operation and micro-power aeration.

PubMed

Yang, Yongqiang; Zhan, Xuan; Wu, Shijun; Kang, Mingliang; Guo, Jianan; Chen, Fanrong

2016-04-01

The low hydraulic loading rate (HLR) greatly restricts the wide application of subsurface wastewater infiltration system (SWIS) in densely populated areas. To increase the HLR, an innovative SWIS was developed using cyclic operation mode. In each cycle, a wastewater feeding period is followed by a drying period, in which the aeration is conducted by a medium-pressure fan. Results indicated that the removal rate of TOC and NH4(+)-N were more than 85% at HLR of 0.5m(3)/m(2)d, whereas the TN removal rate was lower than 20%, indicating that the aeration was efficient and denitrification process was largely limited in the SWIS. When HLR decreased from 0.5 to 0.2m(3)/m(2)d, the pollutant removal efficiency enhanced slightly except for TN. Overall, the intermittent operation and micro-power aeration, combined with shunting the pollutant loading were really helpful for SWIS to achieve higher HLR, which offers a reference for the design of innovative SWIS. Copyright © 2016 Elsevier Ltd. All rights reserved.

Performance assessment of aeration and radial oxygen loss assisted cathode based integrated constructed wetland-microbial fuel cell systems.

PubMed

Srivastava, Pratiksha; Dwivedi, Saurabh; Kumar, Naresh; Abbassi, Rouzbeh; Garaniya, Vikram; Yadav, Asheesh Kumar

2017-11-01

The present study explores low-cost cathode development possibility using radial oxygen loss (ROL) of Canna indica plants and intermittent aeration (IA) for wastewater treatment and electricity generation in constructed wetland-microbial fuel cell (CW-MFC) system. Two CW-MFC microcosms were developed. Amongst them, one microcosm was planted with Canna indica plants for evaluating the ROL dependent cathode reaction (CW-MFC dependent on ROL) and another microcosm was equipped with intermittent aeration for evaluating the intermittent aeration dependent cathode reaction (CW-MFC with additional IA). The CW-MFC with additional IA has achieved 78.71% and 53.23%, and CW-MFC dependent on ROL has achieved 72.17% and 46.77% COD removal from synthetic wastewater containing glucose loads of 0.7gL -1 and 2.0gL -1 , respectively. The maximum power density of 31.04mWm -3 and 19.60mWm -3 was achieved in CW-MFC with additional IA and CW-MFC dependent on ROL, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evolution of the chemistry of Fe bearing waters during CO2 degassing

USGS Publications Warehouse

Geroni, J.N.; Cravotta, C.A.; Sapsford, D.J.

2012-01-01

The rates of Fe(II) oxidation and precipitation from groundwater are highly pH dependent. Elevated levels of dissolved CO2 can depress pH and cause difficulty in removing dissolved Fe and associated metals during treatment of ferruginous water. This paper demonstrates interdependent changes in pH, dissolved inorganic C species, and Fe(II) oxidation rates that occur as a result of the removal (degassing) of CO2 during aeration of waters discharged from abandoned coal mines. The results of field monitoring of aeration cascades at a treatment facility as well as batchwise aeration experiments conducted using net alkaline and net acidic waters in the UK are combined with geochemical modelling to demonstrate the spatial and temporal evolution of the discharge water chemistry. The aeration cascades removed approximately 67% of the dissolved CO2 initially present but varying the design did not affect the concentration of Fe(II) leaving the treatment ponds. Continued removal of the residual CO2 by mechanical aeration increased pH by as much as 2 units and resulted in large increases in the rates of Fe(II) oxidation and precipitation. Effective exsolution of CO2 led to a reduction in the required lime dose for removal of remaining Fe(II), a very important factor with regard to increasing the sustainability of treatment practices. An important ancillary finding for passive treatment is that varying the design of the cascades had little impact on the rate of CO2 removal at the flow rates measured.

Post-Outbreak Investigation of Pseudomonas aeruginosa Faucet Contamination by Quantitative Polymerase Chain Reaction and Environmental Factors Affecting Positivity.

PubMed

Bédard, Emilie; Laferrière, Céline; Charron, Dominique; Lalancette, Cindy; Renaud, Christian; Desmarais, Nadia; Déziel, Eric; Prévost, Michèle

2015-11-01

To perform a post-outbreak prospective study of the Pseudomonas aeruginosa contamination at the faucets (water, aerator and drain) by culture and quantitative polymerase chain reaction (qPCR) and to assess environmental factors influencing occurrence A 450-bed pediatric university hospital in Montreal, Canada Water, aerator swab, and drain swab samples were collected from faucets and analyzed by culture and qPCR for the post-outbreak investigation. Water microbial and physicochemical parameters were measured, and a detailed characterization of the sink environmental and design parameters was performed. The outbreak genotyping investigation identified drains and aerators as the source of infection. The implementation of corrective measures was effective, but post-outbreak sampling using qPCR revealed 50% positivity for P. aeruginosa remaining in the water compared with 7% by culture. P. aeruginosa was recovered in the water, the aerator, and the drain in 21% of sinks. Drain alignment vs the faucet and water microbial quality were significant factors associated with water positivity, whereas P. aeruginosa load in the water was an average of 2 log higher for faucets with a positive aerator. P. aeruginosa contamination in various components of sink environments was still detected several years after the resolution of an outbreak in a pediatric university hospital. Although contamination is often not detectable in water samples by culture, P. aeruginosa is present and can recover its culturability under favorable conditions. The importance of having clear maintenance protocols for water systems, including the drainage components, is highlighted.

Comparison of compostable bags and aerated bins with conventional storage systems to collect the organic fraction of municipal solid waste from homes. a Catalonia case study.

PubMed

Puyuelo, Belén; Colón, Joan; Martín, Patrícia; Sánchez, Antoni

2013-06-01

The separation of biowaste at home is key to improving, facilitating and reducing the operational costs of the treatment of organic municipal waste. The conventional method of collecting such waste and separating it at home is usually done by using a sealed bin with a plastic bag. The use of modern compostable bags is starting to be implemented in some European countries. These compostable bags are made of biodegradable polymers, often from renewable sources. In addition to compostable bags, a new model of bin is also promoted that has a perforated surface that, together with the compostable bag, makes the so-called "aerated system". In this study, different combinations of home collection systems have been systematically studied in the laboratory and at home. The results obtained quantitatively demonstrate that the aerated bin and compostable bag system combination is effective at improving the collection of biowaste without significant gaseous emissions and preparing the organic waste for further composting as concluded from the respiration indices. In terms of weight loss, temperature, gas emissions, respiration index and organic matter reduction, the best results were achieved with the aerated system. At the same time, a qualitative study of bin and bag combinations was carried in 100 homes in which more than 80% of the families participating preferred the aerated system. Copyright © 2013 Elsevier Ltd. All rights reserved.

Evaluation of Toxic Effects of Aeration and Trichloroethylene Oxidation on Methanotrophic Bacteria Grown with Different Nitrogen Sources

PubMed Central

Chu, Kung-Hui; Alvarez-Cohen, Lisa

1999-01-01

In this study we evaluated specific and nonspecific toxic effects of aeration and trichloroethylene (TCE) oxidation on methanotrophic bacteria grown with different nitrogen sources (nitrate, ammonia, and molecular nitrogen). The specific toxic effects, exerted directly on soluble methane monooxygenase (sMMO), were evaluated by comparing changes in methane uptake rates and naphthalene oxidation rates following aeration and/or TCE oxidation. Nonspecific toxic effects, defined as general cellular damage, were examined by using a combination of epifluorescent cellular stains to measure viable cell numbers based on respiratory activity and measuring formate oxidation activities following aeration and TCE transformation. Our results suggest that aeration damages predominantly sMMO rather than other general cellular components, whereas TCE oxidation exerts a broad range of toxic effects that damage both specific and nonspecific cellular functions. TCE oxidation caused sMMO-catalyzed activity and respiratory activity to decrease linearly with the amount of substrate degraded. Severe TCE oxidation toxicity resulted in total cessation of the methane, naphthalene, and formate oxidation activities and a 95% decrease in the respiratory activity of methanotrophs. The failure of cells to recover even after 7 days of incubation with methane suggests that cellular recovery following severe TCE product toxicity is not always possible. Our evidence suggests that generation of greater amounts of sMMO per cell due to nitrogen fixation may be responsible for enhanced TCE oxidation activities of nitrogen-fixing methanotrophs rather than enzymatic protection mechanisms associated with the nitrogenase enzymes. PMID:9925614

Emissions of ammonia, carbon dioxide, and hydrogen sulfide from swine wastewater during and after acidification treatment: effect of pH, mixing and aeration.

PubMed

Dai, X R; Blanes-Vidal, V

2013-01-30

This study aimed at evaluating the effect of swine slurry acidification and acidification-aeration treatments on ammonia (NH(3)), carbon dioxide (CO(2)) and hydrogen sulfide (H(2)S) emissions during slurry treatment and subsequent undisturbed storage. The study was conducted in an experimental setup consisting of nine dynamic flux chambers. Three pH levels (pH = 6.0, pH = 5.8 and pH = 5.5), combined with short-term aeration and venting (with an inert gas) treatments were studied. Acidification reduced average NH(3) emissions from swine slurry stored after acidification treatment compared to emissions during storage of non-acidified slurry. The reduction were 50%, 62% and 77% when pH was reduce to 6.0, 5.8 and 5.5, respectively. However, it had no significant effect on average CO(2) and H(2)S emissions during storage of slurry after acidification. Aeration of the slurry for 30 min had no effect on average NH(3), CO(2) and H(2)S emissions both during the process and from stored slurry after venting treatments. During aeration treatment, the NH(3), CO(2) and H(2)S release pattern observed was related to the liquid turbulence caused by the gas bubbles rather than to biological oxidation processes in this study. Copyright © 2012 Elsevier Ltd. All rights reserved.

Intensification of constructed wetlands for land area reduction: a review.

PubMed

Ilyas, Huma; Masih, Ilyas

2017-05-01

The large land area requirement of constructed wetlands (CWs) is a major limitation of its application especially in densely populated and mountainous areas. This review paper provides insights on different strategies applied for the reduction of land area including stack design and intensification of CWs with different aeration methods. The impacts of different aeration methods on the performance and land area reduction were extensively and critically evaluated for nine wetland systems under three aeration strategies such as tidal flow (TF), effluent recirculation (ER), and artificial aeration (AA) applied on three types of CWs including vertical flow constructed wetland (VFCW), horizontal flow constructed wetland (HFCW), and hybrid constructed wetland (HCW). The area reduction and pollutant removal efficiency showed substantial variation among different types of CWs and aeration strategies. The ER-VFCW designated the smallest footprint of 1.1 ± 0.5 m 2 PE -1 (population equivalent) followed by TF-VFCW with the footprint of 2.1 ± 1.8 m 2 PE -1 , and the large footprint was of AA-HFCW (7.8 ± 4.7 m 2 PE -1 ). When footprint and removal efficiency both are the major indicators for the selection of wetland type, the best options for practical application could be TF-VFCW, ER-HCW, and AA-HCW. The data and results outlined in this review could be instructive for futures studies and practical applications of CWs for wastewater treatment, especially in land-limited regions.

Structure influence on mechanical and acoustic properties of freeze-dried gels obtained with the use of hydrocolloids.

PubMed

Ciurzyńska, Agnieszka; Marzec, Agata; Mieszkowska, Arleta; Lenart, Andrzej

2017-04-01

The influence of the structure formed by the type of hydrocolloids (low-methoxyl pectin, the mixture of xanthan gum, and locust bean gum, and mixture of xanthan gum, and guar gum) and the aeration time (3, 5, 7, and 9 min) on textural properties of freeze-dried gels were investigated. The hardest texture generating the strongest acoustic emission was obtained by freeze-dried pectin gel, characterised by the lowest porosity and the largest pore diameter. Aeration time significantly affected mechanical and acoustic properties of the pectin gel lyophilisate. No effect of gel aeration time on tested characteristics of samples with mixture of hydrocolloids was observed. Strong positive correlations between acoustic energy as well as the maximum force and work and negative ones between porosity and pore diameter indicate that greater resilience and stronger acoustic emission of freeze-dried gels was caused by the reduction of porosity and the increase in the pore size of the material. The research is expected to show the phenomenon of structure formation when preparing and freeze-drying gels and explain the influence of the process parameters (time of aeration, the type of hydrocolloids) on the formation of the internal structure and physical properties of a dried product, especially mechanical and acoustic properties. This achievement will contribute to the development of the science of food and human nutrition, especially within the context of the popular research on aerated diet products. The expected result will be the ability to develop a new technology for producing food with a delicate texture, using the phenomenon of sublimation. As a result, designing changes in the structure of freeze-dried fruit gels with a delicate structure will be possible due to the choice of ingredients and aeration parameters in order to develop innovative food characterised by favorable nutritional, health and functional properties, which will be attractive for the consumers. © 2016 Wiley Periodicals, Inc.

The corrosion effect of ozonated seawater solution on titanium in polymer generated crevice environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leveillee, S.Y.

1998-01-01

Two different tests were designed to evaluate the reaction of various polymers and grade-2 titanium in ozonated seawater in conjunction with a comparative analysis in an aerated seawater solution. The first was a weight loss test measuring the weight change of Polyvinyl chloride (PVC), Polyethylene and Teflon{trademark} in both ozonated and aerated artificial seawater baths. The second test was designed to induce crevice corrosion on the titanium test samples using various crevice generating materials in both ozonated and aerated solutions. The materials used to create the crevices were grade-2 titanium washers, PVC, Polyethylene, Saran and Teflon{trademark}. The weight loss testmore » showed that all three polymers lost weight in the ozonated bath. The results of the titanium washer crevice test provided no indication of corrosion or surface discoloration in either the ozonated or aerated solutions. Energy dispersive spectrometry (EDS) analysis found no fluorine, chlorine or other corrosion product. The PVC samples in the aerated bath also showed no signs of corrosion, but the PVC samples in the ozonated tank had light brown rings of surface discoloration. One of the ozonated PVC samples did show evidence of chlorine in the corrosion product. The outer circumference of the ozonated PVC washers exhibited the same type bleaching effect as in the weight loss samples, but the whitening of these samples were more pronounced. The polyethylene samples under aeration showed no discoloration or presence of fluorine or chlorine. The polyethylene crevice samples in the ozonated solution all exhibited the distinct brilliant blue color of titanium oxide. Fluorine was found in the corrosion product on only one of the samples. Chlorine was found on the surface of one of the other corrosion coupons. The results of the Teflon{trademark} crevice samples substantiated the previous Rensselaer study.« less

Modeling and optimization of poly(3hydroxybutyrate-co-3hydroxyvalerate) production from cane molasses by Azohydromonas lata MTCC 2311 in a stirred-tank reactor: effect of agitation and aeration regimes.

PubMed

Zafar, Mohd; Kumar, Shashi; Kumar, Surendra; Dhiman, Amit K

2012-07-01

The effects of agitation and aeration rates on copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] production by Azohydromonas lata MTCC 2311 using cane molasses supplemented with propionic acid in a bioreactor were investigated. The experiments were conducted in a three-level factorial design by varying the impeller (150-500 rev min(-1)) and aeration (0.5-1.5 vvm) rates. Further, the data were fitted to mathematical models [quadratic polynomial equation and artificial neural network (ANN)] and process variables were optimized by genetic algorithm-coupled models. ANN and hybrid ANN-GA were found superior for modeling and optimization of process variables, respectively. The maximum copolymer concentration of 7.45 g l(-1) with 21.50 mol% of 3HV was predicted at process variables: agitation speed, 287 rev min(-1); and aeration rate, 0.85 vvm, which upon validation gave 7.20 g l(-1) of P(3HB-co-3HV) with 21 mol% of 3HV with the prediction error (%) of 3.38 and 2.32, respectively. Agitation speed established a relative high importance of 72.19% than of aeration rate (27.80%) for copolymer accumulation. The volumetric gas-liquid mass transfer coefficient (k (L) a) was strongly affected by agitation and aeration rates. The highest P(3HB-co-3HV) productivity of 0.163 g l(-1) h(-1) was achieved at 0.17 s(-1) of k (L) a value. During the early phase of copolymer production process, 3HB monomers were accumulated, which were shifted to 3HV units (9-21%) during the cultivation period of 24-42 h. The enhancement of 7.5 and 34% were reported for P(3HB-co-3HV) production and 3HV content, respectively, by hybrid ANN-GA paradigm, which revealed the significant utilization of cane molasses for improved copolymer production.

A numerical analysis of biogeochemical controls with physical modulation on hypoxia during summer in the Pearl River estuary

NASA Astrophysics Data System (ADS)

Wang, Bin; Hu, Jiatang; Li, Shiyu; Liu, Dehong

2017-06-01

A three-dimensional (3-D) physical-biogeochemical coupled model was applied to explore the mechanisms controlling the dissolved oxygen (DO) dynamics and bottom hypoxia during summer in the Pearl River estuary (PRE). By using the numerical oxygen tracers, we proposed a new method (namely the physical modulation method) to quantify the contributions of boundary conditions and each source and sink process occurring in local and adjacent waters to the DO conditions. A mass balance analysis of DO based on the physical modulation method indicated that the DO conditions at the bottom layer were mainly controlled by the source and sink processes, among which the sediment oxygen demand (SOD) at the water-sediment interface and the re-aeration at the air-sea interface were the two primary processes determining the spatial extent and duration of bottom hypoxia in the PRE. The SOD could cause a significant decrease in the bottom DO concentrations (averaged over July-August 2006) by over 4 mg L-1 on the shelf off the Modaomen sub-estuary, leading to the formation of a high-frequency zone of hypoxia (HFZ). However, the hypoxia that occurred in the HFZ was intermittent and distributed in a small area due to the combined effects of re-aeration and photosynthesis, which behaved as sources for DO and offset a portion of the DO consumed by SOD. The bottom DO concentrations to the west of the lower Lingdingyang Bay (i.e. the western shoal near Qi'ao Island) were also largely affected by high SOD, but there was no hypoxia occurring there because of the influence of re-aeration. Specifically, re-aeration could lead to an increase in the bottom DO concentrations by ˜ 4.8 mg L-1 to the west of the lower Lingdingyang Bay. The re-aeration led to a strong vertical DO gradient between the surface and the lower layers. As a result, the majority (˜ 89 %) of DO supplemented by re-aeration was transported to the lower layers through vertical diffusion and ˜ 28 % reached the bottom eventually. Additional numerical experiments showed that turning off re-aeration could lead to an expansion of the hypoxic area from 237 to 2203 km2 and result in persistent hypoxia (hypoxic frequency > 80 %) to the west of the lower Lingdingyang Bay. Compared to re-aeration and SOD, photosynthesis and water column respiration had relatively small impacts on the DO conditions; turning off these two processes increased the hypoxic area to 591 km2. In summary, our study explicitly elucidated the interactive impacts of physical and biogeochemical processes on the DO dynamics in the PRE, which is critical to understanding hypoxia in this shallow and river-dominated estuarine system.

Intensification of ammonia removal from waste water in biologically active zeolitic ion exchange columns.

PubMed

Almutairi, Azel; Weatherley, Laurence R

2015-09-01

The use of nitrification filters for the removal of ammonium ion from waste-water is an established technology deployed extensively in municipal water treatment, in industrial water treatment and in applications such as fish farming. The process involves the development of immobilized bacterial films on a solid packing support, which is designed to provide a suitable host for the film, and allow supply of oxygen to promote aerobic action. Removal of ammonia and nitrite is increasingly necessary to meet drinking water and discharge standards being applied in the US, Europe and other places. Ion-exchange techniques are also effective for removal of ammonia (as the ammonium ion) from waste water and have the advantage of fast start-up times compared to biological filtration which in some cases may take several weeks to be fully operational. Here we explore the performance of ion exchange columns in which nitrifying bacteria are cultivated, with the goal of a "combined" process involving simultaneous ion-exchange and nitrification, intensified by in-situ aeration with a novel membrane module. There were three experimental goals. Firstly, ion exchange zeolites were characterized and prepared for comparative column breakthrough studies for ammonia removal. Secondly effective in-situ aeration for promotion of nitrifying bacterial growth was studied using a number of different membranes including polyethersulfone (PES), polypropylene (PP), nylon, and polytetra-fluoroethylene (PTFE). Thirdly the breakthrough performance of ion exchange columns filled with zeolite in the presence of aeration and in the presence of nitrifying bacteria was determined to establish the influence of biomass, and aeration upon breakthrough during ammonium ion uptake. The methodology adopted included screening of two types of the naturally occuring zeolite clinoptilolite for effective ammonia removal in continuous ion-exchange columns. Next, the performance of fixed beds of clinoptilolite in the presence of nitrifying bacteria is compared to that in columns in which only ion exchange is occurring. The aeration performance of each of the chosen membranes was compared experimentally using a newly developed membrane support module which is also described. Comparison of ammonia removal in columns equipped with in-situ aeration using each membrane was undertaken and the breakthrough characteristics determined. The results showed that ammonia removal in the presence of the nitrifiers was significantly intensified. Column operation with membrane aeration showed further enhancement of ammonia removal. The greatest enhancement was observed in the case of the polyethersulfone membrane (PES). It is concluded that combined nitrification and ion-exchange is significantly intensified in packed columns by in-situ aeration using a novel membrane module. There is significant potential for extending the ion-exchange cycle time and thus potential cost reduction. Copyright © 2015 Elsevier Ltd. All rights reserved.

5. AERATOR VIEW FROM DOWNSTREAM. FLUSH VALVE AT RIGHT OPENS ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. AERATOR VIEW FROM DOWNSTREAM. FLUSH VALVE AT RIGHT OPENS TO CLEAR THE SYSTEM ABOVE THE SILT AND DEBRIS AND TO STOP THE FLOW OF WATER INTO THE SYSTEM DOWN LINE. BOX FLUME CONTINUES DOWN LINE TO SEDIMENTATION CHAMBER. - Kalaupapa Water Supply System, Waikolu Valley to Kalaupapa Settlement, Island of Molokai, Kalaupapa, Kalawao County, HI

Sidewall-box airlift pump provides large flows for aeration, CO2 stripping, and water rotation in large dual-drain circular tanks

USDA-ARS?s Scientific Manuscript database

Conventional gas transfer technologies for aquaculture systems occupy a large amount of space, require a considerable capital investment, and can contribute to high electricity demand. In addition, diffused aeration in a circular culture tank can interfere with the hydrodynamics of water rotation a...

Melde's experiment with an aquarium aerator. Rich dynamics with inexpensive apparatus

NASA Astrophysics Data System (ADS)

Graham, Mark

1998-05-01

As the basis for understanding music, quantum mechanics, and optical phenomena, standing waves are tremendously important, but instructors with a shoestring budget may not be able to do laboratories for them. However with simple modification of an inexpensive aquarium aerator costing a few dollars, instructors can take that shoestring and make standing waves.

Field trial of a new aeration system for enhancing biodegradation in a biopile.

PubMed

Li, L; Cunningham, C J; Pas, Valerie; Philp, J C; Barry, D A; Anderson, P

2004-01-01

The influence of a new aeration system on the biopile performance was investigated. The purpose was to increase biodegradation efficiency by optimising airflow through the pile. During a 1-month field trial, the performance of a new system using two perforated vertical pipes with wind-driven turbines was compared with that of a standard pile configuration with two horizontal perforated pipes. Both piles were composed of a similar mix of diesel-contaminated soils, woodchips, compost and NPK fertiliser. Hydrocarbons were recovered using solvent extraction, and determined both gravimetrically and by gas chromatography. Total heterotrophs, pH and moisture content were also assessed. Air pressure measurements were made to compare the efficiency of suction in the pipes. Results at the end of the experiment showed that there was no significant difference between the two piles in the total amount of hydrocarbon biodegradation. The normalised degradation rate was, however, considerably higher in the new system than in the standard one, suggesting that the vertical venting method may have improved the efficiency of the biological reactions in the pile. The pressure measurements showed a significant improvement in the suction produced by the new aeration system. However, many factors other than the airflow (oxygen supply) may influence and limit the biodegradation rates, including moisture content, age of contaminants and the climatic conditions. Additional experiments and modelling need to be carried out to explore further the new aeration method and to develop criteria and guidelines for engineering design of optimal aeration schemes in order to achieve maximum biodegradation in biopiles.

Landfill aeration for emission control before and during landfill mining.

PubMed

Raga, Roberto; Cossu, Raffaello; Heerenklage, Joern; Pivato, Alberto; Ritzkowski, Marco

2015-12-01

The landfill of Modena, in northern Italy, is now crossed by the new high velocity railway line connecting Milan and Bologna. Waste was completely removed from a part of the landfill and a trench for the train line was built. With the aim of facilitating excavation and further disposal of the material extracted, suitable measures were defined. In order to prevent undesired emissions into the excavation area, the aerobic in situ stabilisation by means of the Airflow technology took place before and during the Landfill Mining. Specific project features involved the pneumatic leachate extraction from the aeration wells (to keep the leachate table low inside the landfill and increase the volume of waste available for air migration) and the controlled moisture addition into a limited zone, for a preliminary evaluation of the effects on process enhancement. Waste and leachate were periodically sampled in the landfill during the aeration before the excavation, for quality assessment over time; the evolution of biogas composition in the landfill body and in the extraction system for different plant set-ups during the project was monitored, with specific focus on uncontrolled migration into the excavation area. Waste biological stability significantly increased during the aeration (waste respiration index dropped to 33% of the initial value after six months). Leachate head decreased from 4 to 1.5m; leachate recirculation tests proved the beneficial effects of moisture addition on temperature control, without hampering waste aerobization. Proper management of the aeration plant enabled the minimization of uncontrolled biogas emissions into the excavation area. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of mix ratio, moisture content and aeration rate on sulfur odor emissions during pig manure composting.

PubMed

Zang, Bing; Li, Shuyan; Michel, Frederick; Li, Guoxue; Luo, Yuan; Zhang, Difang; Li, Yangyang

2016-10-01

Sulfur compounds in swine manure can cause odor emissions during composting if conditions are not conducive to their rapid oxidation and degradation. In this study, the effects of controllable composting process variables on sulfur odor emissions were investigated. These included pig manure to corn stalk mix ratio (0.7:1, 1.5:1 and 2.2:1dw basis), initial moisture content (60%, 65%, 70% and 75%) and aeration rate (1.0, 2.0, 3.0 and 4.0m(3)m(-3)h(-1)). The compounds measured were carbonyl sulfide, carbon disulfide, hydrogen sulfide, methyl mercaptan, ethyl mercaptan, diethyl sulfide, dimethyl sulfide (Me2S) and dimethyl disulfide (Me2SS). The results showed that total sulfur losses ranged from 3.9% to 18.3% after 26days of composting. Me2S and Me2SS were the primary (>59.61%) sulfur compounds released during this period. After turning, emission rates of both Me2S and Me2SS increased. Emissions of the other six sulfur compounds were low and inconsistent during composting. Within the compost, feedstock mix ratio significantly influenced the concentration of Me2SS, while aeration rate significantly affected Me2S concentration (p<0.05). Moisture content did not have a significant effect on the concentrations of either of these two compounds. Concentrations of sulfur odor compounds were the lowest at the highest aeration rate. Therefore, high aeration rates during the thermophilic phase, especially after turning, are recommended to minimize sulfur odors produced during swine manure composting. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of soil amendment with different carbon sources and other factors on the bioremediation of an aged PAH-contaminated soil.

PubMed

Teng, Ying; Luo, Yongming; Ping, Lifeng; Zou, Dexun; Li, Zhengao; Christie, Peter

2010-04-01

Carbon supplementation, soil moisture and soil aeration are believed to enhance in situ bioremediation of PAH-contaminated soils by stimulating the growth of indigenous microorganisms. However, the effects of added carbon and nitrogen together with soil moisture and soil aeration on the dissipation of PAHs and on associated microbial counts have yet to be fully assessed. In this study the effects on bioremediation of carbon source, carbon-to-nitrogen ratio, soil moisture and aeration on an aged PAH-contaminated agricultural soil were studied in microcosms over a 90-day period. Additions of starch, glucose and sodium succinate increased soil bacterial and fungal counts and accelerated the dissipation of phenanthrene and benzo(a)pyrene in soil. Decreases in phenanthrene and benzo(a)pyrene concentrations were effective in soil supplemented with glucose and sodium succinate (both 0.2 g C kg(-1) dry soil) and starch (1.0 g C kg(-1) dry soil). The bioremediation effect at a C/N ratio of 10:1 was significantly higher (P < 0.05) than at a C/N of either 25:1 or 40:1. Soil microbial counts and PAH dissipation were lower in the submerged soil but soil aeration increased bacterial and fungal counts, enhanced indigenous microbial metabolic activities, and accelerated the natural degradation of phenanthrene and benzo(a)pyrene. The results suggest that optimizing carbon source, C/N ratio, soil moisture and aeration conditions may be a feasible remediation strategy in certain PAH contaminated soils with large active microbial populations.

Mathematical model for carbon dioxide evolution from the thermophilic composting of synthetic food wastes made of dog food

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, J.I.; Tsai, J.J.; Wu, K.H.

2005-07-01

The impacts of the aeration and the agitation on the composting process of synthetic food wastes made of dog food were studied in a laboratory-scale reactor. Two major peaks of CO{sub 2} evolution rate were observed. Each peak represented an independent stage of composting associated with the activities of thermophilic bacteria. CO{sub 2} evolutions known to correlate well with microbial activities and reactor temperatures were fitted successfully to a modified Gompertz equation, which incorporated three biokinetic parameters, namely, CO{sub 2} evolution potential, specific CO{sub 2} evolution rate, and lag phase time. No parameters that describe the impact of operating variablesmore » are involved. The model is only valid for the specified experimental conditions and may look different with others. The effects of operating parameters such as aeration and agitation were studied statistically with multivariate regression technique. Contour plots were constructed using regression equations for the examination of the dependence of CO{sub 2} evolution potentials on aeration and agitation. In the first stage, a maximum CO{sub 2} evolution potential was found when the aeration rate and the agitation parameter were set at 1.75 l/kg solids-min and 0.35, respectively. In the second stage, a maximum existed when the aeration rate and the agitation parameter were set at 1.8 l/kg solids-min and 0.5, respectively. The methods presented here can also be applied for the optimization of large-scale composting facilities that are operated differently and take longer time.« less

Effects of aeration on water quality from septic system leachfields.

PubMed

Potts, David A; Görres, Josef H; Nicosia, Erika L; Amador, José A

2004-01-01

We conducted a pilot-scale study at a research facility in southeastern Connecticut to assess the effects of leachfield aeration on removal of nutrients and pathogens from septic system effluent. Treatments consisted of lysimeters periodically aerated to maintain a headspace O(2) concentration of 0.209 mol mol(-1) (AIR) or vented to an adjacent leachfield trench (LEACH) and were replicated three times. All lysimeters were dosed with effluent from a septic tank for 24 mo at a rate of 12 cm d(-1) and subsequently for 2 mo at 4 cm d(-1). LEACH lysimeters had developed a clogging mat, or biomat, 20 mo before the beginning of our study. The level of aeration in the AIR treatment was held constant regardless of loading rate. No conventional biomat developed in the AIR treatment, whereas a biomat was present in the LEACH lysimeters. The headspace of LEACH lysimeters was considerably depleted in O(2) and enriched in CH(4), CO(2), and H(2)S relative to AIR lysimeters. Drainage water from AIR lysimeters was saturated with O(2) and had significantly lower pH, five-day biological oxygen demand (BOD(5)), and ammonium, and higher levels of nitrate and sulfate than LEACH lysimeters regardless of dosing rate. By contrast, significantly lower levels of total N and fecal coliform bacteria were observed in AIR than in LEACH lysimeters only at the higher dosing rate. No significant differences in total P removal were observed. Our results suggest that aeration may improve the removal of nitrogen, BOD(5), and fecal coliforms in leachfield soil, even in the absence of a biomat.

Key role of alternative oxidase in lovastatin solid-state fermentation.

PubMed

Pérez-Sánchez, Ailed; Uribe-Carvajal, Salvador; Cabrera-Orefice, Alfredo; Barrios-González, Javier

2017-10-01

Lovastatin is a commercially important secondary metabolite produced by Aspergillus terreus, either by solid-state fermentation or by submerged fermentation. In a previous work, we showed that reactive oxygen species (ROS) accumulation in idiophase positively regulates lovastatin biosynthetic genes. In addition, it has been found that lovastatin-specific production decreases with aeration in solid-state fermentation (SSF). To study this phenomenon, we determined ROS accumulation during lovastatin SSF, under high and low aeration conditions. Paradoxically, high aeration caused lower ROS accumulation, and this was the underlying reason of the aeration effect on lovastatin production. Looking for a mechanism that is lowering ROS production under those conditions, we studied alternative respiration. The alternative oxidase provides an alternative route for electrons passing through the electron transport chain to reduce oxygen. Here, we showed that an alternative oxidase (AOX) is expressed in SSF, and only during idiophase. It was shown that higher aeration induces higher alternative respiration (AOX activity), and this is a mechanism that limits ROS generation and keeps them within healthy limits and adequate signaling limits for lovastatin production. Indeed, the aox gene was induced in idiophase, i.e., at the time of ROS accumulation. Moreover, exogenous ROS (H 2 O 2 ), added to lovastatin solid-state fermentation, induced higher AOX activity. This suggests that high O 2 availability in SSF generates dangerously high ROS, so alternative respiration is induced in SSF, indirectly favoring lovastatin production. Conversely, alternative respiration was not detected in lovastatin-submerged fermentation (SmF), although exogenous ROS also induced relatively low AOX activity in SmF.

Nitrogen Removal over Nitrite by Aeration Control in Aerobic Granular Sludge Sequencing Batch Reactors

PubMed Central

Lochmatter, Samuel; Maillard, Julien; Holliger, Christof

2014-01-01

This study investigated the potential of aeration control for the achievement of N-removal over nitrite with aerobic granular sludge in sequencing batch reactors. N-removal over nitrite requires less COD, which is particularly interesting if COD is the limiting parameter for nutrient removal. The nutrient removal performances for COD, N and P have been analyzed as well as the concentration of nitrite-oxidizing bacteria in the granular sludge. Aeration phase length control combined with intermittent aeration or alternate high-low DO, has proven to be an efficient way to reduce the nitrite-oxidizing bacteria population and hence achieve N-removal over nitrite. N-removal efficiencies of up to 95% were achieved for an influent wastewater with COD:N:P ratios of 20:2.5:1. The total N-removal rate was 0.18 kgN·m−3·d−1. With N-removal over nitrate the N-removal was only 74%. At 20 °C, the nitrite-oxidizing bacteria concentration decreased by over 95% in 60 days and it was possible to switch from N-removal over nitrite to N-removal over nitrate and back again. At 15 °C, the nitrite-oxidizing bacteria concentration decreased too but less, and nitrite oxidation could not be completely suppressed. However, the combination of aeration phase length control and high-low DO was also at 15 °C successful to maintain the nitrite pathway despite the fact that the maximum growth rate of nitrite-oxidizing bacteria at temperatures below 20 °C is in general higher than the one of ammonium-oxidizing bacteria. PMID:25006970

A Guide for Developing Standard Operating Job Procedures for the Activated Sludge - Aeration & Sedimentation Process Wastewater Treatment Facility. SOJP No. 5.

ERIC Educational Resources Information Center

Mason, George J.

This guide for developing standard operating job procedures for wastewater treatment facilities is devoted to the activated sludge aeration and sedimentation process. This process is for conversion of nonsettleable and nonfloatable materials in wastewater to settleable, floculated biological groups and separation of the settleable solids from the…

SUPERFUND TREATABILITY CLEARINGHOUSE: PILOT STUDY OF ENCLOSED THERMAL SOIL AERATION FOR REMOVAL OF VOLATILE ORGANIC CONTAMINATION AT THE MCKIN SUPERFUND SITE

EPA Science Inventory

This paper reports on the results of a pilot study that treated vadose zone soil contaminated with VOCs in an enclosed thermal aeration system. The McKin site, an NPL site in Grey, Maine, was the location of the pilot study. The pilot study was chosen to demonstrate the viabili...

Poor Aeration Curtails Slash Pine Root Growth and Nutrient Uptake

Treesearch

Eugene Shoulders

1976-01-01

Slash pine may absorb nutrients and water best in spring and early summer because soil moisture, soil aeration, and temperature are apparently optimum at this time. One-year-old slash pine seedlings maintained at a high oxygen level grew about 1% times as many roots as were produced at a low oxygen level. No other environmental conditions significantly influenced root...

Burkholderia pseudomallei traced to water treatment plant in Australia.

PubMed

Inglis, T J; Garrow, S C; Henderson, M; Clair, A; Sampson, J; O'Reilly, L; Cameron, B

2000-01-01

Burkholderia pseudomallei was isolated from environmental specimens 1 year after an outbreak of acute melioidosis in a remote coastal community in northwestern Australia. B. pseudomallei was isolated from a water storage tank and from spray formed in a pH-raising aerator unit. Pulsed-field gel electrophoresis confirmed the aerator and storage tank isolates were identical to the outbreak strain, WKo97.

4. AERATOR AT 525', CONSTRUCTED 19371938, VIEW FROM UPSTREAM (TRASH ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. AERATOR AT 525', CONSTRUCTED 1937-1938, VIEW FROM UPSTREAM (TRASH SCREEN REMOVED FOR CLARITY), WATER FROM INTAKE FLOWS THROUGH FLUME, THEN DAMS, AND SPILLS OVER STEPS TO MIX WITH OXYGEN, THUS REDUCING ACIDITY LEVELS. ACID INDUCES FASTER CORROSION OF PIPES AND SPOILS TASTE. - Kalaupapa Water Supply System, Waikolu Valley to Kalaupapa Settlement, Island of Molokai, Kalaupapa, Kalawao County, HI

Computational Fluid Dynamics Simulation of Flows in an Oxidation Ditch Driven by a New Surface Aerator.

PubMed

Huang, Weidong; Li, Kun; Wang, Gan; Wang, Yingzhe

2013-11-01

In this article, we present a newly designed inverse umbrella surface aerator, and tested its performance in driving flow of an oxidation ditch. Results show that it has a better performance in driving the oxidation ditch than the original one with higher average velocity and more uniform flow field. We also present a computational fluid dynamics model for predicting the flow field in an oxidation ditch driven by a surface aerator. The improved momentum source term approach to simulate the flow field of the oxidation ditch driven by an inverse umbrella surface aerator was developed and validated through experiments. Four kinds of turbulent models were investigated with the approach, including the standard k - ɛ model, RNG k - ɛ model, realizable k - ɛ model, and Reynolds stress model, and the predicted data were compared with those calculated with the multiple rotating reference frame approach (MRF) and sliding mesh approach (SM). Results of the momentum source term approach are in good agreement with the experimental data, and its prediction accuracy is better than MRF, close to SM. It is also found that the momentum source term approach has lower computational expenses, is simpler to preprocess, and is easier to use.

Effects of the rate of releases from Sam Rayburn Reservoir on the Aeration Capacity of the Angelina River, eastern Texas

USGS Publications Warehouse

Rawson, Jack; Goss, Richard L.; Rathbun, Ira G.

1980-01-01

A three-phase study was conducted during July and August 1979 to determine the effects of varying release rates through the power-outlet works at Sam Rayburn Reservoir, eastern Texas, on aeration capacity of a 14-mile reach of the Angelina River below Sam Rayburn Dam. The dominant factors that affected the aeration capacity during the study time were time of travel and the dissolved-oxygen deficit of the releases. Aeration was low throughout the study but increased in response to increases in the dissolved-oxygen deficit and the duration of time that the releases were exposed to the atmosphere (time of travel). The average concentration of dissolved oxygen sustained by release of 8,800 cubic feet per second decreased from 5.0 milligrams per liter at a site near the power outlet to 4.8 milligrams per liter at a site about 14 miles downstream; the time of travel averaged about 8 hours. The average concentration of dissolved oxygen in flow sustained by releases of 2,200 cubic feet per second increased from 5.2 to 5.5 milligrams per liter; the time of travel averaged about 20 hours. (USGS)

Degradation of municipal solid waste in simulated landfill bioreactors under aerobic conditions.

PubMed

Slezak, Radoslaw; Krzystek, Liliana; Ledakowicz, Stanislaw

2015-09-01

In this study the municipal solid waste degradation processes in simulated landfill bioreactors under aerobic and anaerobic conditions is investigated. The effect of waste aeration on the dynamics of the aerobic degradation processes in lysimeters as well as during anaerobic processes after completion of aeration is presented. The results are compared with the anaerobic degradation process to determine the stabilization stage of waste in both experimental modes. The experiments in aerobic lysimeters were carried out at small aeration rate (4.41⋅10(-3)lmin(-1)kg(-1)) and for two recirculation rates (24.9 and 1.58lm(-3)d(-1)). The change of leachate and formed gases composition showed that the application of even a small aeration rate favored the degradation of organic matter. The amount of CO2 and CH4 released from anaerobic lysimeter was about 5 times lower than that from the aerobic lysimeters. Better stabilization of the waste was obtained in the aerobic lysimeter with small recirculation, from which the amount of CO2 produced was larger by about 19% in comparison with that from the aerobic lysimeter with large leachate recirculation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Wastewater treatment for nutrient removal with Ecuadorian native microalgae.

PubMed

Benítez, María Belén; Champagne, Pascale; Ramos, Ana; Torres, Andres F; Ochoa-Herrera, Valeria

2018-04-12

The aim of this project was to study the feasibility of utilizing native microalgae for the removal of nitrogen and phosphorus, as a potential secondary wastewater treatment process in Ecuador. Agitation and aeration batch experiments were conducted using synthetic secondary wastewater effluent, to determine nitrogen and phosphorus removal efficiencies by a native Ecuadorian microalgal strain. Experimental results indicated that microalgal cultures could successfully remove nitrogen and phosphorus. [Formula: see text] and [Formula: see text] removal efficiencies of 52.6 and 55.6%, and 67.0 and 20.4%, as well as [Formula: see text] production efficiencies of 87.0 and 93.1% were reported in agitation and aeration photobioreactors, respectively. Aeration was not found to increase the nutrient removal efficiency of [Formula: see text]. Moreover, in the case of [Formula: see text], a negative impact was observed, where removal efficiencies decreased by a factor of 3.3 at higher aeration rates. To the best of our knowledge, this is the first report of the removal of nutrients by native Ecuadorian Chlorella sp., hence the results of this study would indicate that this native microalgal strain could be successfully incorporated in a potential treatment process for nutrient removal in Ecuador.

Constructed wetland using corncob charcoal substrate: pollutants removal and intensification.

PubMed

Liu, Mao; Li, Boyuan; Xue, Yingwen; Wang, Hongyu; Yang, Kai

2017-09-01

To investigate the feasibility of using corncob charcoal substrate in constructed wetlands, four laboratory-scale vertical flow constructed wetlands (VFCWs) were built. Effluent pollutant (chemical oxygen demand (COD), NH 4 + -N, total phosphorus (TP)) concentrations during the experiment were determined to reveal pollutant removal mechanisms and efficiencies at different stages. In the stable stage, a VFCW using clay ceramisite substrate under aeration attained higher COD (95.1%), and NH 4 + -N (95.1%) removal efficiencies than a VFCW using corncob charcoal substrate (91.5% COD, 91.3% NH 4 + -N) under aeration, but lower TP removal efficiency (clay ceramisite 32.0% and corncob charcoal 40.0%). The VFCW with raw corncob substrate showed stronger COD emissions (maximum concentration 3,108 mg/L) than the corncob charcoal substrate (COD was lower than influent). The VFCW using corncob charcoal substrate performed much better than the VFCW using clay ceramisite substrate under aeration when the C/N ratio was low (C/N = 1.5, TN removal efficiency 36.89%, 4.1% respectively). These results suggest that corncob charcoal is a potential substrate in VFCWs under aeration with a unique self -supplying carbon source property in the denitrification process.

Diversity of thermophilic populations during thermophilic aerobic digestion of potato peel slurry.

PubMed

Ugwuanyi, J O; Harvey, L M; McNeil, B

2008-01-01

To study the diversity of thermophiles during thermophilic aerobic digestion (TAD) of agro-food waste slurries under conditions similar to full-scale processes. Population diversity and development in TAD were studied by standard microbiological techniques and the processes monitored by standard fermentation procedures. Facultative thermophiles were identified as Bacillus coagulans and B. licheniformis, while obligate thermophiles were identified as B. stearothermophilus. They developed rapidly to peaks of 10(7) to 10(8) in

Development of observational learning during school formation in jack mackerel Trachurus japonicus juveniles.

PubMed

Takahashi, Kohji; Masuda, Reiji; Yamashita, Yoh

2014-03-01

We assessed whether the development of observational learning in jack mackerel Trachurus japonicus juveniles corresponds with that of their schooling behaviour. Schooling behaviour was quantitatively analyzed by nearest neighbour distance and separation angle in two size classes of fish, 20-mm and 40-mm in body length. Observer and non-observer fish with matching sizes were conditioned to pellets by temporarily stopping aeration. Observer fish were provided with five observation trials of other individuals feeding near an air stone when aeration was stopped. After the observation trial, fish were conditioned to pellets with the stop of aeration, and then the learning process was evaluated by the increase in the association with the feeding area when aeration was stopped. In 20-mm fish, which were at an immature stage of schooling behaviour, there was no difference in the learning process between observer and non-observer fish. In contrast, 40-mm fish were confirmed to have a well-developed schooling behaviour, and the observer learnt the feeding area more efficiently than the non-observer. This study provides evidence that observational learning develops along with the development of the social interaction. Copyright © 2013 Elsevier B.V. All rights reserved.

Process Optimization on Micro-Aeration Supply for High Production Yield of 2,3-Butanediol from Maltodextrin by Metabolically-Engineered Klebsiella oxytoca

PubMed Central

Jantama, Sirima Suvarnakuta; Kanchanatawee, Sunthorn

2016-01-01

An optimization process with a cheap and abundant substrate is considered one of the factors affecting the price of the production of economical 2,3-Butanediol (2,3-BD). A combination of the conventional method and response surface methodology (RSM) was applied in this study. The optimized levels of pH, aeration rate, agitation speed, and substrate concentration (maltodextrin) were investigated to determine the cost-effectiveness of fermentative 2,3-BD production by metabolically-engineered Klebsiella oxytoca KMS005. Results revealed that pH, aeration rate, agitation speed, and maltodextrin concentration at levels of 6.0, 0.8 vvm, 400 rpm, and 150 g/L respectively were the optimal conditions. RSM also indicated that the agitation speed was the most influential parameter when either agitation and aeration interaction or agitation and substrate concentration interaction played important roles for 2,3-BD production by the strain from maltodextrin. Under interim fed-batch fermentation, 2,3-BD concentration, yield, and productivity were obtained at 88.1±0.2 g/L, 0.412±0.001 g/g, and 1.13±0.01 g/L/h respectively within 78 h. PMID:27603922

Evaluation of bioaugmentation efficiency for the treatment of run-off water under tropical conditions: applications to the Derby-Tacaruna canal (Recife/Brazil).

PubMed

da Silva, M C L; Nascimento, A M; da Silva, V L; Pons, M N; da Motta, M

2009-01-01

An evaluation of the efficiency of bacterial biomass augmentation was performed at lab-scale for the pollution treatment of the Derby-Tacaruna canal. The canal is located at the central area of Great Recife, alongside an important urban corridor. The characterization of the canal water in different tidal conditions showed that the actual pollution is organic and inorganic (heavy metals). Degradation experiments of water from the canal and rain-off system polluted by synthetic wastewater were performed, using activated sludge and an industrial bioadditive. Continuous reactors under two different conditions were evaluated: with diffuse aeration and without aeration. The channel reactor was operated under steady state conditions at a flow rate of 2.5 L h(-1) and with an average residence time of 22 h without aeration and 17 h with aeration. The organic matter removal was in the range of 60% for the system inoculated with the bioadditive and 85% with activated sludge. It was concluded that the water of the Derby-Tacaruna canal may be treated by activated sludge without being affected by its salt content, while the bioaugmentation technique was not satisfactory due to inhibition by inorganics.

Cost-effective treatment solutions for rural areas: design and operation of a new package treatment plant for single households.

PubMed

Daude, D; Stephenson, T

2003-01-01

The design approach and operation of a newly developed package plant treating domestic sewage from single households were evaluated. Combining submerged aerated filter (SAF) technology with jet aeration and incorporating both into a compact and shallow tank resulted in a cost-effective treatment solution. A trial unit was permanently installed at a rural site, serving a single household. Jet aeration proved to be the best aeration method for the shallow bioreactor design. Further trials revealed a 50% reduction in suspended solids (SS) through the use of a static effluent filter and found that annual plant maintenance was vital to sustain stable operating conditions. Despite high variations in influent conditions, the trial unit produced good effluent quality during steady-state operation. Average effluent BOD5, COD and SS values were 19.6 mg l(-1), 98 mg l(-1) and 32 mg l(-1) achieving overall removal efficiencies of 94.2%, 85.9% and 87.6% respectively. However, effluent ammonia nitrogen (NH4-N) levels were found to be inconsistent varying from 9 mg l(-1) to over 60 mg l(-1).

Lung aeration on post-mortem magnetic resonance imaging is a useful marker of live birth versus stillbirth.

PubMed

Barber, Joy L; Sebire, Neil J; Chitty, Lyn S; Taylor, Andrew M; Arthurs, Owen J

2015-05-01

Aim of this study was to investigate whether lung assessment on post-mortem magnetic resonance imaging (PMMR) can reliably differentiate between live birth and stillbirth. We retrospectively assessed PMMR imaging features of a group of late foetal terminations following fetocide and stillbirths (without witnessed breathing) and early infant deaths (breathed spontaneously before death). PMMR images were reviewed for evidence of lung aeration and other features, blinded to the clinical and autopsy data. Nineteen infant deaths (mean age 3.0 ± 6.5 post-natal weeks) and 23 foetal terminations or stillbirths (mean age 32.6 ± 10.2-week gestation) were compared. Subjective appearances of lung aeration on PMMR were the best indicator of live birth, with a sensitivity of 89.5% (95% confidence interval 68.6, 97.1%) and specificity of 95.6% (79.0, 99.2%) and positive and negative predictive values of 94.4% and 91.7%, respectively. Lung aeration on PMMR appears to have high overall accuracy for confirmation of live birth versus intrauterine foetal death but now requires validating in a larger cohort of perinatal deaths.

Nitrous oxide emissions from one-step partial nitritation/anammox processes.

PubMed

Yang, Jingjing; Trela, Jozef; Plaza, Elzbieta

2016-12-01

Measurements of nitrous oxide were made at pilot- and full-scale plants to evaluate greenhouse gas emissions from one-step partial nitritation/anammox processes applied in moving bed biofilm reactors treating reject water. It was found that 0.51-1.29% and 0.35-1.33% of the total nitrogen loads in the pilot- and full-scale reactor, respectively, were emitted as nitrous oxide. Between 80 and 90% of nitrous oxide emissions were in gaseous form and the rest amount was found in the reactor effluent; over 90% of nitrous oxide emissions occurred in the aerated period and less than 8% in the non-aerated period in the full-scale study. Nitrous oxide productions/consumptions were closely related to aeration and the nitrogen loads applied in the system.

Validation of a multi-phase plant-wide model for the description of the aeration process in a WWTP.

PubMed

Lizarralde, I; Fernández-Arévalo, T; Beltrán, S; Ayesa, E; Grau, P

2018-02-01

This paper introduces a new mathematical model built under the PC-PWM methodology to describe the aeration process in a full-scale WWTP. This methodology enables a systematic and rigorous incorporation of chemical and physico-chemical transformations into biochemical process models, particularly for the description of liquid-gas transfer to describe the aeration process. The mathematical model constructed is able to reproduce biological COD and nitrogen removal, liquid-gas transfer and chemical reactions. The capability of the model to describe the liquid-gas mass transfer has been tested by comparing simulated and experimental results in a full-scale WWTP. Finally, an exploration by simulation has been undertaken to show the potential of the mathematical model. Copyright © 2017 Elsevier Ltd. All rights reserved.

Passive aerobic treatment of net-alkaline, iron-laden drainage from a flooded underground anthracite mine, Pennsylvania, USA

USGS Publications Warehouse

Cravotta, C.A.

2007-01-01

This report evaluates the results of a continuous 4.5-day laboratory aeration experiment and the first year of passive, aerobic treatment of abandoned mine drainage (AMD) from a typical flooded underground anthracite mine in eastern Pennsylvania, USA. During 1991-2006, the AMD source, locally known as the Otto Discharge, had flows from 20 to 270 L/s (median 92 L/s) and water quality that was consistently suboxic (median 0.9 mg/L O2) and circumneutral (pH ??? 6.0; net alkalinity >10) with moderate concentrations of dissolved iron and manganese and low concentrations of dissolved aluminum (medians of 11, 2.2, and <0.2 mg/L, respectively). In 2001, the laboratory aeration experiment demonstrated rapid oxidation of ferrous iron (Fe 2+) without supplemental alkalinity; the initial Fe2+ concentration of 16.4 mg/L decreased to less than 0.5 mg/L within 24 h; pH values increased rapidly from 5.8 to 7.2, ultimately attaining a steady-state value of 7.5. The increased pH coincided with a rapid decrease in the partial pressure of carbon dioxide (PCO2) from an initial value of 10 -1.1atm to a steady-state value of 10-3.1atm. From these results, a staged aerobic treatment system was conceptualized consisting of a 2 m deep pond with innovative aeration and recirculation to promote rapid oxidation of Fe2+, two 0.3 m deep wetlands to facilitate iron solids removal, and a supplemental oxic limestone drain for dissolved manganese and trace-metal removal. The system was constructed, but without the aeration mechanism, and began operation in June 2005. During the first 12 months of operation, estimated detention times in the treatment system ranged from 9 to 38 h. However, in contrast with 80-100% removal of Fe2+ over similar elapsed times during the laboratory aeration experiment, the treatment system typically removed less than 35% of the influent Fe2+. Although concentrations of dissolved CO2 decreased progressively within the treatment system, the PCO2 values for treated effluent remained elevated (10-2.4 to 10-1.7atm). The elevated PCO 2 maintained the pH within the system at values less than 7 and hence slowed the rate of Fe2+ oxidation compared to the aeration experiment. Kinetic models of Fe2+ oxidation that consider effects of pH and dissolved O2 were incorporated in the geochemical computer program PHREEQC to evaluate the effects of detention time, pH, and other variables on Fe2+ oxidation and removal rates. These models and the laboratory aeration experiment indicate that performance of this and other aerobic wetlands for treatment of net-alkaline AMD could be improved by aggressive, continuous aeration in the initial stage to decrease PCO 2, increase pH, and accelerate Fe2+ oxidation. ?? 2007 Springer-Verlag.

Local Soils Information Needed to Define the Root Zone in Process Models on the Gulf Coastal Plain

Treesearch

Mary Anne Sword Sayer; Allan E. Tiarks

2002-01-01

We combined published information and our own experimental results from the Gulf Coastal Plain to evaluate how soil aeration and strength interact with loblolly pine root growth. Our results demonstrate that soil aeration and strength differ by soil series and year and are subject to vertical and horizontal spatial variation. Comparison of loblolly pine root phenology...

Burkholderia pseudomallei traced to water treatment plant in Australia.

PubMed Central

Inglis, T. J.; Garrow, S. C.; Henderson, M.; Clair, A.; Sampson, J.; O'Reilly, L.; Cameron, B.

2000-01-01

Burkholderia pseudomallei was isolated from environmental specimens 1 year after an outbreak of acute melioidosis in a remote coastal community in northwestern Australia. B. pseudomallei was isolated from a water storage tank and from spray formed in a pH-raising aerator unit. Pulsed-field gel electrophoresis confirmed the aerator and storage tank isolates were identical to the outbreak strain, WKo97. PMID:10653571

Enhanced Al and Zn removal from coal-mine drainage during rapid oxidation and precipitation of Fe oxides at near-neutral pH

USGS Publications Warehouse

Burrows, Jill E.; Cravotta, Charles A.; Peters, Stephen C.

2017-01-01

Net-alkaline, anoxic coal-mine drainage containing ∼20 mg/L FeII and ∼0.05 mg/L Al and Zn was subjected to parallel batch experiments: control, aeration (Aer 1 12.6 mL/s; Aer 2 16.8 mL/s; Aer 3 25.0 mL/s), and hydrogen peroxide (H2O2) to test the hypothesis that aeration increases pH, FeII oxidation, hydrous FeIII oxide (HFO) formation, and trace-metal removal through adsorption and coprecipitation with HFO. During 5.5-hr field experiments, pH increased from 6.4 to 6.7, 7.1, 7.6, and 8.1 for the control, Aer 1, Aer 2, and Aer 3, respectively, but decreased to 6.3 for the H2O2 treatment. Aeration accelerated removal of dissolved CO2, Fe, Al, and Zn. In Aer 3, dissolved Al was completely removed within 1 h, but increased to ∼20% of the initial concentration after 2.5 h when pH exceeded 7.5. H2O2 promoted rapid removal of all dissolved Fe and Al, and 13% of dissolved Zn.Kinetic modeling with PHREEQC simulated effects of aeration on pH, CO2, Fe, Zn, and Al. Aeration enhanced Zn adsorption by increasing pH and HFO formation while decreasing aqueous CO2 available to form ZnCO30 and Zn(CO3)22− at high pH. Al concentrations were inconsistent with solubility control by Al minerals or Al-containing HFO, but could be simulated by adsorption on HFO at pH < 7.5 and desorption at higher pH where Al(OH)4− was predominant. Thus, aeration or chemical oxidation with pH adjustment to ∼7.5 could be effective for treating high-Fe and moderate-Zn concentrations, whereas chemical oxidation without pH adjustment may be effective for treating high-Fe and moderate-Al concentrations.

Combined effects of agitation and aeration on the chitinolytic enzymes production by the Antarctic fungus Lecanicillium muscarium CCFEE 5003

PubMed Central

2012-01-01

Background The Antarctic fungus Lecanicillium muscarium CCFEE 5003 is one of the most powerful chitinolytic organisms. It can produce high level of chitinolytic enzymes in a wide range of temperatures (5-30°C). Chitinolytic enzymes have lot of applications but their industrial production is still rather limited and no cold-active enzymes are produced. In view of massive production of L. muscarium chitinolytic enzymes, its cultivation in bioreactors is mandatory. Microbial cultivation and/or their metabolite production in bioreactors are sometime not possible and must be verified and optimized for possible exploitation. Agitation and aeration are the most important parameters in order to allow process up-scaling to the industrial level. Results In this study, submerged cultures of L. muscarium CCFEE 5003 were carried out in a 2-L bench-top CSTR bioreactor in order to optimise the production of chitinolytic enzymes. The effect of stirrer speed (range 200-500 rpm) and aeration rate (range 0.5-1.5 vvm) combination was studied, by Response Surface Methodology (RSM), in a medium containing 1.0% yeast nitrogen base and 1% colloidal chitin. Optimization was carried out, within a "quadratic D-optimal" model, using quantitative and quantitative-multilevel factors for aeration and agitation, respectively. The model showed very good correlation parameters (R2, 0.931; Q2, 0.869) and the maximum of activity (373.0 U/L) was predicted at ca. 327 rpm and 1.1 vvm. However, the experimental data showed that highest activity (383.7 ± 7.8 U/L) was recorded at 1 vvm and 300 rpm. Evident shear effect caused by stirrer speed and, partially, by high aeration rates were observed. Under optimized conditions in bioreactor the fungus was able to produce a higher number of chitinolytic enzymes than those released in shaken flasks. In addition, production was 23% higher. Conclusions This work demonstrated the attitude of L. muscarium CCFEE 5003 to grow in bench-top bioreactor; outlined the strong influence of aeration and agitation on its growth and enzyme production and identified the optimal conditions for possible production at the industrial level. PMID:22270226

Stable isotope signatures for characterising the biological stability of landfilled municipal solid waste.

PubMed

Wimmer, Bernhard; Hrad, Marlies; Huber-Humer, Marion; Watzinger, Andrea; Wyhlidal, Stefan; Reichenauer, Thomas G

2013-10-01

Stable isotopic signatures of landfill leachates are influenced by processes within municipal solid waste (MSW) landfills mainly depending on the aerobic/anaerobic phase of the landfill. We investigated the isotopic signatures of δ(13)C, δ(2)H and δ(18)O of different leachates from lab-scale experiments, lysimeter experiments and a landfill under in situ aeration. In the laboratory, columns filled with MSW of different age and reactivity were percolated under aerobic and anaerobic conditions. In landfill simulation reactors, waste of a 25year old landfill was kept under aerobic and anaerobic conditions. The lysimeter facility was filled with mechanically shredded fresh waste. After starting of the methane production the waste in the lysimeter containments was aerated in situ. Leachate and gas composition were monitored continuously. In addition the seepage water of an old landfill was collected and analysed periodically before and during an in situ aeration. We found significant differences in the δ(13)C-value of the dissolved inorganic carbon (δ(13)C-DIC) of the leachate between aerobic and anaerobic waste material. During aerobic degradation, the signature of δ(13)C-DIC was mainly dependent on the isotopic composition of the organic matter in the waste, resulting in a δ(13)C-DIC of -20‰ to -25‰. The production of methane under anaerobic conditions caused an increase in δ(13)C-DIC up to values of +10‰ and higher depending on the actual reactivity of the MSW. During aeration of a landfill the aerobic degradation of the remaining organic matter caused a decrease to a δ(13)C-DIC of about -20‰. Therefore carbon isotope analysis in leachates and groundwater can be used for tracing the oxidation-reduction status of MSW landfills. Our results indicate that monitoring of stable isotopic signatures of landfill leachates over a longer time period (e.g. during in situ aeration) is a powerful and cost-effective tool for characterising the biodegradability and stability of the organic matter in landfilled municipal solid waste and can be used for monitoring the progress of in situ aeration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Study on two operating conditions of a full-scale oxidation ditch for optimization of energy consumption and effluent quality by using CFD model.

PubMed

Yang, Yin; Yang, Jiakuan; Zuo, Jiaolan; Li, Ye; He, Shu; Yang, Xiao; Zhang, Kai

2011-05-01

The operating condition of an oxidation ditch (OD) has significant impact on energy consumption and effluent quality of wastewater treatment plants (WWTPs). An experimentally validated numerical tool, based on computational fluid dynamics (CFD) model, was proposed to optimize the operating condition by considering two important factors: flow field and dissolved oxygen (DO) concentration profiles. The model is capable of predicting flow pattern and oxygen mass transfer characteristics in ODs equipped with surface aerators and submerged impellers. Performance demonstration and comparison of two operating conditions (existing and improved) were carried out in two full-scale Carrousel ODs at the Ping Dingshan WWTP in Henan, China. A moving wall model and a fan model were designed to simulate surface aerators and submerged impellers, respectively. Oxygen mass transfer in the ditch was predicted by using a unit analysis method. In aeration zones, the mass inlets representing the surface aerators were set as one source of DO. In the whole straight channel, the oxygen consumption was modeled by using modified BOD-DO model. The following results were obtained: (1) the CFD model characterized flow pattern and DO concentration profiles in the full-scale OD. The predicted flow field values were within 1.98 ± 4.28% difference from the actual measured values while the predicted DO concentration values were within -4.71 ± 4.15% of the measured ones, (2) a surface aerator should be relocated to around 15m from the curve bend entrance to reduce energy loss caused by fierce collisions at the wall of the curve bend, and (3) DO concentration gradients in the OD under the improved operating condition were more favorable for occurrence of simultaneous nitrification and denitrification (SND). Copyright © 2011 Elsevier Ltd. All rights reserved.

Increase in pulmonary blood flow at birth: role of oxygen and lung aeration.

PubMed

Lang, Justin A R; Pearson, James T; Binder-Heschl, Corinna; Wallace, Megan J; Siew, Melissa L; Kitchen, Marcus J; te Pas, Arjan B; Fouras, Andreas; Lewis, Robert A; Polglase, Graeme R; Shirai, Mikiyasu; Hooper, Stuart B

2016-03-01

Lung aeration stimulates the increase in pulmonary blood flow (PBF) at birth, but the spatial relationships between PBF and lung aeration and the role of increased oxygenation remain unclear. Using simultaneous phase-contrast X-ray imaging and angiography, we have investigated the separate roles of lung aeration and increased oxygenation in PBF changes at birth using near-term (30 days of gestation) rabbit kits (n = 18). Rabbits were imaged before ventilation, then the right lung was ventilated with 100% nitrogen (N2), air or 100% O2 (oxygen), before all kits were switched to ventilation in air, followed by ventilation of both lungs using air. Unilateral ventilation of the right lung with 100% N2 significantly increased heart rate (from 69.4 ± 4.9 to 93.0 ± 15.0 bpm), the diameters of both left and right pulmonary axial arteries, number of visible vessels in both left and right lungs, relative PBF index in both pulmonary arteries, and reduced bolus transit time for both left and right axial arteries (from 1.34 ± 0.39 and 1.81 ± 0.43 s to 0.52 ± 0.17 and 0.89 ± 0.21 s in the left and right axial arteries, respectively). Similar changes were observed with 100% oxygen, but increases in visible vessel number and vessel diameter of the axial arteries were greater in the ventilated right lung during unilateral ventilation. These findings confirm that PBF increase at birth is not spatially related to lung aeration and that the increase in PBF to unventilated regions is unrelated to oxygenation, although oxygen can potentiate this increase. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

Who contributes more to N2O emission during sludge bio-drying with two different aeration strategies, nitrifiers or denitrifiers?

PubMed

Zhang, Junya; Wang, Yuanyue; Yu, Dawei; Tong, Juan; Chen, Meixue; Sui, Qianwen; ChuLu, BuHe; Wei, Yuansong

2017-04-01

Global warming effects have drawn more and more attention to studying all sources and sinks of nitrous oxide (N 2 O). Sludge bio-drying, as an effective sludge treatment technology, is being adopted worldwide. In this study, two aeration strategies (piles I and II) were compared to investigate the primary contributors to N 2 O emission during sludge bio-drying through studying the evolution of functional genes involved in nitrification (amoA, hao, and nxrA) and denitrification (narG, nirS, nirK, norB, and nosZ) by quantitative PCR (qPCR). Results showed that the profile of N 2 O emission can be divided into three stages, traditional denitrification contributed largely to N 2 O emission at stage I (days 1-5), but N 2 O emission mainly happened at stage II (days 5-14) due to nitrifier denitrification and NH 2 OH accumulation by ammonia-oxidizing bacteria (AOB), accounting for 51.4% and 58.2% of total N 2 O emission for piles I and II, respectively. At stage III (days 14-21), nitrifier denitrification was inhibited because sludge bio-drying proceeded mainly by the physical aeration, thus N 2 O emission decreased and changed little. The improved aeration strategy availed pile I to reduce N 2 O emission much especially at stages II and III, respectively. These results indicated that nitrifier denitrification by AOB and biological NH 2 OH oxidation due to AOB made more contribution to N 2 O emission, and aeration strategy was crucial to mitigate N 2 O emission during sludge bio-drying.

Greenhouse gas emission from covered windrow composting with controlled ventilation.

PubMed

Ermolaev, Evgheni; Pell, Mikael; Smårs, Sven; Sundberg, Cecilia; Jönsson, Håkan

2012-02-01

Data on greenhouse gas (GHG) emissions from full-scale composting of municipal solid waste, investigating the effects of process temperature and aeration combinations, is scarce. Oxygen availability affects the composition of gases emitted during composting. In the present study, two experiments with three covered windrows were set up, treating a mixture of source separated biodegradable municipal solid waste (MSW) fractions from Uppsala, Sweden, and structural amendment (woodchips, garden waste and re-used compost) in the volume proportion 1:2. The effects of different aeration and temperature settings on the emission of methane (CH(4)), nitrous oxide (N(2)O) and carbon dioxide (CO(2)) during windrow composting with forced aeration following three different control schemes were studied. For one windrow, the controller was set to keep the temperature below 40 °C until the pH increased, another windrow had minimal aeration at the beginning of the process and the third one had constant aeration. In the first experiment, CH(4) concentrations (CH(4):CO(2) ratio) increased, from around 0.1% initially to between 1 and 2% in all windrows. In the second experiment, the initial concentrations of CH(4) displayed similar patterns of increase between windrows until day 12, when concentration peaked at 3 and 6%, respectively, in two of the windrows. In general, the N(2)O fluxes remained low (0.46 ± 0.02 ppm) in the experiments and were two to three times the ambient concentrations. In conclusion, the emissions of CH(4) and N(2)O were low regardless of the amount of ventilation. The data indicates a need to perform longer experiments in order to observe further emission dynamics.

Computational Fluid Dynamics Simulation of Flows in an Oxidation Ditch Driven by a New Surface Aerator

PubMed Central

Huang, Weidong; Li, Kun; Wang, Gan; Wang, Yingzhe

2013-01-01

Abstract In this article, we present a newly designed inverse umbrella surface aerator, and tested its performance in driving flow of an oxidation ditch. Results show that it has a better performance in driving the oxidation ditch than the original one with higher average velocity and more uniform flow field. We also present a computational fluid dynamics model for predicting the flow field in an oxidation ditch driven by a surface aerator. The improved momentum source term approach to simulate the flow field of the oxidation ditch driven by an inverse umbrella surface aerator was developed and validated through experiments. Four kinds of turbulent models were investigated with the approach, including the standard k−ɛ model, RNG k−ɛ model, realizable k−ɛ model, and Reynolds stress model, and the predicted data were compared with those calculated with the multiple rotating reference frame approach (MRF) and sliding mesh approach (SM). Results of the momentum source term approach are in good agreement with the experimental data, and its prediction accuracy is better than MRF, close to SM. It is also found that the momentum source term approach has lower computational expenses, is simpler to preprocess, and is easier to use. PMID:24302850

Membrane-aerated biofilm proton and oxygen flux during chemical toxin exposure.

PubMed

McLamore, E S; Zhang, W; Porterfield, D M; Banks, M K

2010-09-15

Bioreactors containing sessile bacteria (biofilms) grown on hollow fiber membranes have been used for treatment of many wastestreams. Real time operational control of bioreactor performance requires detailed knowledge of the relationship between bulk liquid water quality and physiological transport at the biofilm-liquid interface. Although large data sets exist describing membrane-aerated bioreactor effluent quality, very little real time data is available characterizing boundary layer transport under physiological conditions. A noninvasive, microsensor technique was used to quantify real time (≈1.5 s) changes in oxygen and proton flux for mature Nitrosomonas europaea and Pseudomonas aeruginosa biofilms in membrane-aerated bioreactors following exposure to environmental toxins. Stress response was characterized during exposure to toxins with known mode of action (chlorocarbonyl cyanide phenyl-hydrazone and potassium cyanide), and four environmental toxins (rotenone, 2,4-dinitrophenol, cadmium chloride, and pentachlorophenol). Exposure to sublethal concentrations of all environmental toxins caused significant increases in O(2) and/or H(+) flux (depending on the mode of action). These real time microscale signatures (i.e., fingerprints) of O(2) and H(+) flux can be coupled with bulk liquid analysis to improve our understanding of physiology in counter-diffusion biofilms found within membrane aerated bioreactors; leading to enhanced monitoring/modeling strategies for bioreactor control.

Evaluation of humic substances during co-composting of sewage sludge and corn stalk under different aeration rates.

PubMed

Li, Shuyan; Li, Danyang; Li, Jijin; Li, Guoxue; Zhang, Bangxi

2017-12-01

Sewage sludge and corn stalk were co-composted under different aeration rates 0.12 (AR0.12), 0.24 (AR0.24), 0.36 (AR0.36)L·kg -1 DMmin -1 , respectively. Transformation of humic substance was evaluated by a series of chemical and spectroscopic methods to reveal compost humification. Results showed that aeration rate could significantly affect compost stability and humification process. Humic acid contents in AR0.24 were significantly higher than those in the other two treatments. The final humic acid/fulvic acid ratios in AR0.12, AR0.24 and AR0.36 treatment were 1.0, 1.9 and 0.8, respectively, corresponding to the final E 4 /E 6 of 4.7, 3.2 and 5.5. Moreover, compost in AR0.24 treatment had a high stability degree due to the low C/N atom ratio and high C/H atom ratio. However, it is noteworthy that composting could not significantly affect the structure of HA in a 35-day period. These results indicate that composting with the aeration rate of 0.24L·kg -1 DMmin -1 could accelerated the humification process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthetic musk emissions from wastewater aeration basins.

PubMed

Upadhyay, Nabin; Sun, Qinyue; Allen, Jonathan O; Westerhoff, Paul; Herckes, Pierre

2011-01-01

Wastewater aeration basins at publicly owned treatment works (POTWs) can be emission sources for gaseous or aerosolized sewage material. In the present study, particle and gas phase emissions of synthetic musks from covered and uncovered aeration basins were measured. Galaxolide (HHCB), tonalide (AHTN), and celestolide (ADBI) were the most abundant, ranging from 6704 to 344,306 ng m(-3), 45-3816 ng m(-3), and 2-148 ng m(-3) in the gas phase with particle phase concentrations 3 orders of magnitude lower. The musk species were not significantly removed from the exhaust air by an odor control system, yielding substantial daily emission fluxes (∼ 200 g d(-1) for HHCB) into the atmosphere. However, simple dispersion modeling showed that the treatment plants are unlikely to be a major contributor to ambient air concentrations of these species. Emission of synthetic musk species during wastewater treatment is a substantial fate process; more than 14% of the influent HHCB is emitted to the atmosphere in a POTW as opposed to the <1% predicted by an octanol-water partition coefficient and fugacity-based US EPA fate model. The substantial atmospheric emission of these compounds is most likely due to active stripping that occurs in the aeration basins by bubbling air through the sludge. Copyright © 2010 Elsevier Ltd. All rights reserved.

Computational fluid dynamics simulations of membrane filtration process adapted for water treatment of aerated sewage lagoons.

PubMed

Cano, Grégory; Mouahid, Adil; Carretier, Emilie; Guasp, Pascal; Dhaler, Didier; Castelas, Bernard; Moulin, Philippe

2015-01-01

The aim of this study is to apply the membrane bioreactor technology in an oxidation ditch in submerged conditions. This new wastewater filtration process will benefit rural areas (<5,000 population equivalent) subject to chronic water shortages by reusing this water for irrigation of green areas. For this purpose, the membranes developed without support are immersed in an aeration well and work in suction mode. The development of the membrane without support and more precisely the performance of spacers are approached by computational fluid dynamics in order to provide the best compromise between pressure drop/flow velocity and permeate flux. The numerical results on the layout and the membrane modules' geometry in the aeration well indicate that the optimal configuration is to install the membranes horizontally on three levels. Membranes should be connected to each other to a manifold providing a total membrane area of 18 m². Loss rate compared to the theoretical throughput is relatively low (less than 3%). Preliminary data obtained by modeling the lagoon provide access to its hydrodynamics, revealing that recirculation zones can be optimized by making changes in the operating conditions. The experimental validation of these results and taking into account the aeration in the numerical models are underway.

Aeration control strategies to stimulate simultaneous nitrification-denitrification via nitrite during the formation of aerobic granular sludge.

PubMed

Dobbeleers, Thomas; D'aes, Jolien; Miele, Solange; Caluwé, Michel; Akkermans, Veerle; Daens, Dominique; Geuens, Luc; Dries, Jan

2017-09-01

In this study, a sequencing batch reactor (SBR), treating synthetic wastewater (COD/N = 5), was operated in two stages. During stage I, an aeration control strategy based on oxygen uptake rate (OUR) was applied, to accomplish nitrogen removal via nitrite >80%. In stage II, the development of aerobic granular sludge (AGS) was examined while two aeration control strategies (OUR and pH slope) maintained the nitrite pathway and optimized the simultaneous nitrification-denitrification (SND) performance. Stimulation of slow-growing organisms, (denitrifying) polyphosphate-accumulating organisms (D)PAO and (denitrifying) glycogen-accumulating organisms (D)GAO leads to full granulation (at day 200, SVI 10  = 47.0 mL/g and SVI 30  = 43.1 mL/g). The average biological nutrient removal efficiencies, for nitrogen and phosphorus, were 94.6 and 83.7%, respectively. Furthermore, the benefits of an increased dissolved oxygen concentration (1.0-2.0 mg O 2 /L) were shown as biomass concentrations increased with approximately 2 g/L, and specific ammonium removal rate and phosphorus uptake rate increased with 33 and 44%, respectively. It was shown that the combination of both aeration phase-length control strategies provided an innovative method to achieve SND via nitrite in AGS.

Supersonic Injection of Aerated Liquid Jet

NASA Astrophysics Data System (ADS)

Choudhari, Abhijit; Sallam, Khaled

2016-11-01

A computational study of the exit flow of an aerated two-dimensional jet from an under-expanded supersonic nozzle is presented. The liquid sheet is operating within the annular flow regime and the study is motivated by the application of supersonic nozzles in air-breathing propulsion systems, e.g. scramjet engines, ramjet engines and afterburners. The simulation was conducted using VOF model and SST k- ω turbulence model. The test conditions included: jet exit of 1 mm and mass flow rate of 1.8 kg/s. The results show that air reaches transonic condition at the injector exit due to the Fanno flow effects in the injector passage. The aerated liquid jet is alternately expanded by Prandtl-Meyer expansion fan and compressed by oblique shock waves due to the difference between the back (chamber) pressure and the flow pressure. The process then repeats itself and shock (Mach) diamonds are formed at downstream of injector exit similar to those typical of exhaust plumes of propulsion system. The present results, however, indicate that the flow field of supersonic aerated liquid jet is different from supersonic gas jets due to the effects of water evaporation from the liquid sheet. The contours of the Mach number, static pressure of both cases are compared to the theory of gas dynamics.

The response of nitrous oxide emissions to different operating conditions in activated sludge wastewater treatment plants in Southeastern Brazil.

PubMed

Ribeiro, Renato P; Bueno, Rodrigo F; Piveli, Roque P; Kligerman, Débora C; de Mello, William Z; Oliveira, Jaime L M

2017-11-01

The continuous measurements of N 2 O emissions from the aeration tanks of three activated sludge wastewater treatment plants (WWTPs) operated with biological nitrogen removal (BNR) and non-BNR were performed during the different operating conditions of several parameters, such as aeration, dissolved oxygen (DO) profiling and organic shock loading (with landfill leachate). The nitrification process is the main driving force behind N 2 O emission peaks. There are indications that the variation of the air flow rate influenced N 2 O emissions; high N 2 O emissions denote over-aeration conditions or incomplete nitrification, with accumulation of NO 2 - concentrations. Thus, continuous measurements of N 2 O emissions can provide information on aeration adequacy and the efficiency of complete nitrification, with major focus on DO control, in order to reduce N 2 O emissions. An additional concern is the observed propensity of WWTPs in developing countries to receive landfill leachates in their wastewater systems. This practice could have adverse effects on climate change, since wastewater treatment during periods of organic shock loading emitted significantly higher amounts of N 2 O than without organic shock loading. In short, non-BNR WWTPs are subject to high N 2 O emissions, in contrast to BNR WWTP with controlled nitrification and denitrification processes.

Recovery of elemental sulphur from anaerobic effluents through the biological oxidation of sulphides.

PubMed

de Sousa, José Tavares; Lima, Jéssyca de Freitas; da Silva, Valquíria Cordeiro; Leite, Valderi Duarte; Lopes, Wilton Silva

2017-03-01

The aim of the present study was to evaluate the biological oxidation of sulphide in two different UASB reactors by assessing the occurrence of oxidized forms of sulphur in the effluents and the amount of S 0 that could be recovered in the process. The bioreactors employed were an anaerobic hybrid (AH) reactor employing porous polyurethane foam as support media and a micro-aerated UASB reactor equipped with an aeration device above the digestion zone. The AH reactor produced a final effluent containing low concentrations of S 2- (3.87% of total sulphur load). It was achieved due to a complete oxidation of 56.1% of total sulphur. The partial biological oxidation that occurred in the AH reactor allowed the recovery of 30% of the sulphur load as S 0 . The effluent from the micro-aerated UASB reactor contained 5% of the sulphur load in the form of S 2- , while 20.9% was present as dissolved SO 4 2- and 46% was precipitated as S 0 . It is concluded that the AH reactor or micro-aeration carried out above the digestion zone of the UASB reactor favoured the biological oxidation of S 2- and the release of odourless effluents. Both technologies represent feasible and low-cost alternatives for the anaerobic treatment of domestic sewage.

Ability of an alkali-tolerant mutant strain of the microalga Chlorella sp. AT1 to capture carbon dioxide for increasing carbon dioxide utilization efficiency.

PubMed

Kuo, Chiu-Mei; Lin, Tsung-Hsien; Yang, Yi-Chun; Zhang, Wen-Xin; Lai, Jinn-Tsyy; Wu, Hsi-Tien; Chang, Jo-Shu; Lin, Chih-Sheng

2017-11-01

An alkali-tolerant Chlorella sp. AT1 mutant strain was screened by NTG mutagenesis. The strain grew well in pH 6-11 media, and the optimal pH for growth was 10. The CO 2 utilization efficiencies of Chlorella sp. AT1 cultured with intermittent 10% CO 2 aeration for 10, 20 and 30min at 3-h intervals were approximately 80, 42 and 30%, respectively. In alkaline medium (pH=11) with intermittent 10% CO 2 aeration for 30min at 3-, 6- and 12-h intervals, the medium pH gradually changed to 10, and the biomass productivities of Chlorella sp. AT1 were 0.987, 0.848 and 0.710gL -1 d -1 , respectively. When Chlorella sp. AT1 was aerated with 10% CO 2 intermittently for 30min at 3-h intervals in semi-continuous cultivation for 21days, the biomass concentration and biomass productivity were 4.35gL -1 and 0.726gL -1 d -1 , respectively. Our results show that CO 2 utilization efficiency can be markedly increased by intermittent CO 2 aeration and alkaline media as a CO 2 -capturing strategy for alkali-tolerant microalga cultivation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Full scale evaluation of diffuser ageing with clean water oxygen transfer tests.

PubMed

Krampe, J

2011-01-01

Aeration is a crucial part of the biological wastewater treatment in activated sludge systems and the main energy user of WWTPs. Approximately 50 to 60% of the total energy consumption of a WWTP can be attributed to the aeration system. The performance of the aeration system, and in the case of fine bubble diffused aeration the diffuser performance, has a significant impact on the overall plant efficiency. This paper seeks to isolate the changes of the diffuser performance over time by eliminating all other influencing parameters like sludge retention time, surfactants and reactor layout. To achieve this, different diffusers have been installed and tested in parallel treatment trains in two WWTPs. The diffusers have been performance tested in clean water tests under new conditions and after one year of operation. A set of material property tests describing the diffuser membrane quality was also performed. The results showed a significant drop in the performance of the EPDM diffuser in the first year which resulted in similar oxygen transfer efficiency around 16 g/m3/m for all tested systems. Even though the tested silicone diffusers did not show a drop in performance they had a low efficiency in the initial tests. The material properties indicate that the EPDM performance loss is partly due to the washout of additives.

Assessment of diffuser pressure loss on WWTPs in Baden-Württemberg.

PubMed

Krampe, J

2011-01-01

Aeration of activated sludge is a critical treatment step for the operation of activated sludge plants. To achieve a cost effective treatment process, assessing and benchmarking of aeration system performance are important measures. A simple means of gauging the relative condition of a fine bubble diffused aeration system is to evaluate the pressure loss of the diffusers as oxygen transfer tests are rarely applied during the lifetime of an aeration system. This paper shows an assessment of fine bubble diffuser systems in Baden-Württemberg, Germany, based on the results of a questionnaire sent to 941 WWTPs. Apart from the results with regards to the diffuser pressure loss, this paper also presents information on the current state of diffuser technology such as types and materials as well as the diffuser cleaning methods used in Baden-Württemberg. The majority of the WWTPs were equipped with tube diffusers (71%) with 50% of all plants having EPDM membranes installed. Regular mechanical cleaning is the most common cleaning method followed by regular pressure release/air-bumping programs during operations. With regard to the diffuser pressure loss it was found that 50% of the evaluated plants had a diffuser pressure loss that was twice as high as measured for new diffusers.

Whole systems thinking for sustainable water treatment design

NASA Astrophysics Data System (ADS)

Huggins, Mitchell Tyler

Microbial fuel cell (MFC) technology could provide a low cost alternative to conventional aerated wastewater treatment, however there has been little comparison between MFC and aeration treatment using real wastewater substrate. This study attempts to directly compare the wastewater treatment efficiency and energy consumption and generation among three reactor systems, a traditional aeration process, a simple submerged MFC configuration, and a control reactor acting similar as natural lagoons. Results showed that all three systems were able to remove >90% of COD, but the aeration used shorter time (8 days) then the MFC (10 days) and control reactor (25 days). Compared to aeration, the MFC showed lower removal efficiency in high COD concentration but much higher efficiency when the COD is low. Only the aeration system showed complete nitrification during the operation, reflected by completed ammonia removal and nitrate accumulation. Suspended solid measurements showed that MFC reduced sludge production by 52-82% as compared to aeration, and it also saved 100% of aeration energy. Furthermore, though not designed for high power generation, the MFC reactor showed a 0.3 Wh/g COD/L or 24 Wh/m3 (wastewater treated) net energy gain in electricity generation. These results demonstrate that MFC technology could be integrated into wastewater infrastructure to meet effluent quality and save operational cost. The high cost and life-cycle impact of electrode materials is one major barrier to the large scale application of microbial fuel cells (MFC). We also demonstrate that biomass-derived black carbon (biochar), could be a more cost effective and sustainable alternative to granular activated carbon (GAC) and graphite granule (GG) electrodes. In a comparison study, two biochar materials made from lodgepole pine sawdust pellets (BCp) and lodgepole pine woodchips (BCc), gassified at a highest heat temperature (HHT) of 1000°C under a heating rate of 16°C/min, showed a satisfactory power density of 532 +/- 18 mW/m-2 and 457 +/- 20 mW/m-2 respectively, compared to GAC with 674 +/- 10 mW/m-2 and GG with 566 +/- 5 mW/m-2 (normalized to cathode projected surface area), as an anode material in a two-chamber MFC. BCc and BCp had BET-N2 surface area measurements of 429 cm2 g -1 and 470 cm2 g-1 respectively, lower than industrial GAC with 1248 cm2 g-1 but several orders of magnitude higher that GG with 0.44 cm2 g-1 . BCc and BCp had a lower surface resistance of 3+/-1Ω mm -1 and 6+/-1 Ω mm-1 than 8+/-2Ω mm -1 for GAC, but higher that GG with 0.4+/-0.5 Ω mm -1. We also investigated the life-cycle impact and estimated cost of biochar as an electrode material. Although there is no well-established market price for biochar, conservative estimates place the costs around 51-356 US/tonne, up to ten times cheaper that GAC (500-2500 US/tonne) and GGs (500-800 US$/tonne) with significantly greater life-cycle advantages.

A Trade Study of Two Membrane-Aerated Biological Water Processors

NASA Technical Reports Server (NTRS)

Allada, Ram; Lange, Kevin; Vega. Leticia; Roberts, Michael S.; Jackson, Andrew; Anderson, Molly; Pickering, Karen

2011-01-01

Biologically based systems are under evaluation as primary water processors for next generation life support systems due to their low power requirements and their inherent regenerative nature. This paper will summarize the results of two recent studies involving membrane aerated biological water processors and present results of a trade study comparing the two systems with regards to waste stream composition, nutrient loading and system design. Results of optimal configurations will be presented.

Turbine Aeration Design Software for Mitigating Adverse Environmental Impacts Resulting From Conventional Hydropower Turbines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gulliver, John S.

2015-03-01

Conventional hydropower turbine aeration test-bed for computational routines and software tools for improving environmental mitigation technologies for conventional hydropower systems. In achieving this goal, we have partnered with Alstom, a global leader in energy technology development and United States power generation, with additional funding from the Initiative for Renewable Energy and the Environment (IREE) and the College of Science and Engineering (CSE) at the UMN

Stimulation of waste decomposition in an old landfill by air injection.

PubMed

Wu, Chuanfu; Shimaoka, Takayuki; Nakayama, Hirofumi; Komiya, Teppei; Chai, Xiaoli

2016-12-01

Three pilot-scale lysimeters were operated for 4.5years to quantify the change in the carbon and nitrogen pool in an old landfill under various air injection conditions. The results indicate that air injection at the bottom layer facilitated homogeneous distribution of oxygen in the waste matrix. Substantial total organic carbon (TOC) decomposition and methane generation reduction were achieved. Considerable amount of nitrogen was removed, suggesting that in situ nitrogen removal via the effective simultaneous nitrification and denitrification mechanism is viable. Moreover, material mass change measurements revealed a slight mass reduction of aged MSW (by approximately 4.0%) after 4.5years of aeration. Additionally, experiments revealed that intensive aeration during the final stage of the experiment did not further stimulate the degradation of the aged MSW. Therefore, elimination of the labile fraction of aged MSW should be considered the objective of in situ aeration. Copyright © 2016 Elsevier Ltd. All rights reserved.

Process and system for treating waste water

DOEpatents

Olesen, Douglas E.; Shuckrow, Alan J.

1978-01-01

A process of treating raw or primary waste water using a powdered, activated carbon/aerated biological treatment system is disclosed. Effluent turbidities less than 2 JTU (Jackson turbidity units), zero TOC (total organic carbon) and in the range of 10 mg/l COD (chemical oxygen demand) can be obtained. An influent stream of raw or primary waste water is contacted with an acidified, powdered, activated carbon/alum mixture. Lime is then added to the slurry to raise the pH to about 7.0. A polyelectrolyte flocculant is added to the slurry followed by a flocculation period -- then sedimentation and filtration. The separated solids (sludge) are aerated in a stabilization sludge basin and a portion thereof recycled to an aerated contact basin for mixing with the influent waste water stream prior to or after contact of the influent stream with the powdered, activated carbon/alum mixture.

[Detection of anaerobic processes and microorganisms in immobilized activated sludge of a wastewater treatment plant with intense aeration].

PubMed

Litti, Iu V; Nekrasova, V K; Kulikov, N I; Siman'kova, M V; Nozhevnikova, A N

2013-01-01

Attached activated sludge from the Krasnaya Polyana (Sochi) wastewater treatment plant was studied after the reconstruction by increased aeration and water recycle, as well as by the installation of a bristle carrier for activated sludge immobilization. The activated sludge biofilms developing under conditions of intense aeration were shown to contain both aerobic and anaerobic microorganisms. Activity of a strictly anaerobic methanogenic community was revealed, which degraded organic compounds to methane, further oxidized by aerobic methanotrophs. Volatile fatty acids, the intermediates of anaerobic degradation of complex organic compounds, were used by both aerobic and anaerobic microorganisms. Anaerobic oxidation of ammonium with nitrite (anammox) and the presence of obligate anammox bacteria were revealed in attached activated sludge biofilms. Simultaneous aerobic and anaerobic degradation of organic contaminants by attached activated sludge provides for high rates of water treatment, stability of the activated sludge under variable environmental conditions, and decreased excess sludge formation.

Cashew apple juice as microbial cultivation medium for non-immunogenic hyaluronic acid production.

PubMed

Oliveira, Adriano H; Ogrodowski, Cristiane C; de Macedo, André C; Santana, Maria Helena A; Gonçalves, Luciana R B

2013-12-01

In this work, natural cashew apple juice was used as cultivation medium as an alternative to substitute brain heart infusion medium. The effect of aeration and juice supplementation with yeast extract on the production of hyaluronic acid in batch fermentation was also investigated. Similar levels of cell mass were obtained in inoculum using cashew apple juice supplemented with yeast extract or the conventional brain heart infusion medium. Fermentation in Erlenmeyer flasks produced low biomass and hyaluronic acid concentrations. The hyaluronic acid concentration and viscosity increased from 0.15 g/L and 3.87 cP (no aeration or medium supplementation) to 1.76 g/L and 107 cP, when aeration (2 vvm) and 60 g/L of yeast extract were used. The results suggest the production of low-molecular weight hyaluronic acid oligomers instead of the high molecular weight polymer.

[Mechanism of the organic pollutant degradation in water by hybrid gas-liquid electrical discharge].

PubMed

Zhu, Li-nan; Ma, Jun; Yang, Shi-dong

2007-09-01

The method of hybrid gas-liquid electrical discharge was investigated for the removal of phenol. The results indicate that this new method can remove phenol in water effectively. The removal rate increases with increasing voltage and air aeration. The production quantity of H2O2 and O3 is measured respectively in the discharge region and the production quantity increases with increasing of voltage and air aeration. The energy consumption analysis indicates that with increasing the voltage, the increase extent of the phenol removal rate is smaller than the energy's, so the increase of energy efficiency is very small. Air aeration increases the energy consumption. At the same time, a considerable part of energy in the overall input energy makes the temperature of the solution increase, and more energy is transformed into heat, which leads to the waste of energy.

Measuring a critical stress for continuous prevention of marine biofouling accumulation with aeration.

PubMed

Menesses, Mark; Belden, Jesse; Dickenson, Natasha; Bird, James

2017-10-01

When cleaning the hull of a ship, significant shear stresses are needed to remove established biofouling organisms. Given that there exists a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. Yet, it is unclear if there is a minimum stress needed to prevent the growth of macrofouling in the limit of continuous grooming. This manuscript shows that single bubble stream aeration provides continuous grooming and prevents biofouling accumulation in regions where the average wall stress exceeds ~0.01 Pa. This value was found by comparing observations of biofouling growth from field studies with complementary laboratory measurements that probe the associated flow fields. These results suggest that aeration and other continuous grooming systems must exceed a wall stress of 0.01 Pa to prevent macrofouling accumulation.

Binary effect of fly ash and palm oil fuel ash on heat of hydration aerated concrete.

PubMed

Mehmannavaz, Taha; Ismail, Mohammad; Radin Sumadi, Salihuddin; Rafique Bhutta, Muhammad Aamer; Samadi, Mostafa; Sajjadi, Seyed Mahdi

2014-01-01

The binary effect of pulverized fuel ash (PFA) and palm oil fuel ash (POFA) on heat of hydration of aerated concrete was studied. Three aerated concrete mixes were prepared, namely, concrete containing 100% ordinary Portland cement (control sample or Type I), binary concrete made from 50% POFA (Type II), and ternary concrete containing 30% POFA and 20% PFA (Type III). It is found that the temperature increases due to heat of hydration through all the concrete specimens especially in the control sample. However, the total temperature rises caused by the heat of hydration through both of the new binary and ternary concrete were significantly lower than the control sample. The obtained results reveal that the replacement of Portland cement with binary and ternary materials is beneficial, particularly for mass concrete where thermal cracking due to extreme heat rise is of great concern.

Binary Effect of Fly Ash and Palm Oil Fuel Ash on Heat of Hydration Aerated Concrete

PubMed Central

Mehmannavaz, Taha; Ismail, Mohammad; Radin Sumadi, Salihuddin; Rafique Bhutta, Muhammad Aamer; Samadi, Mostafa

2014-01-01

The binary effect of pulverized fuel ash (PFA) and palm oil fuel ash (POFA) on heat of hydration of aerated concrete was studied. Three aerated concrete mixes were prepared, namely, concrete containing 100% ordinary Portland cement (control sample or Type I), binary concrete made from 50% POFA (Type II), and ternary concrete containing 30% POFA and 20% PFA (Type III). It is found that the temperature increases due to heat of hydration through all the concrete specimens especially in the control sample. However, the total temperature rises caused by the heat of hydration through both of the new binary and ternary concrete were significantly lower than the control sample. The obtained results reveal that the replacement of Portland cement with binary and ternary materials is beneficial, particularly for mass concrete where thermal cracking due to extreme heat rise is of great concern. PMID:24696646

Partial Insulation of Aerated Concrete Wall in its Thermal Bridge Regions

NASA Astrophysics Data System (ADS)

Li, Baochang; Guo, Lirong; Li, Yubao; Zhang, Tiantian; Tan, Yufei

2018-01-01

As a self-insulating building material which can meet the 65 percent energy-efficiency requirements in cold region of China, aerated concrete blocks often go moldy, frost heaving, or cause plaster layer hollowing at thermal bridge parts in the extremely cold regions due to the restrictions of environmental climate and construction technique. In this paper, partial insulation measures of the thermal-bridge position of these parts of aerated concrete walls are designed to weaken or even eliminate thermal bridge effect and improve the temperature of thermal-bridge position. A heat transfer calculation model for L-shaped wall and T-shaped wall is developed. Based on the simulation result, the influence of the thickness on the temperature field is analyzed. Consequently, the condensation inside self-thermal-insulating wall and frost heaving caused by condensation and low temperature will be reduced, avoiding damage to the wall body from condensation..

Cashew apple juice as microbial cultivation medium for non-immunogenic hyaluronic acid production

PubMed Central

Oliveira, Adriano H.; Ogrodowski, Cristiane C.; de Macedo, André C.; Santana, Maria Helena A.; Gonçalves, Luciana R.B.

2013-01-01

In this work, natural cashew apple juice was used as cultivation medium as an alternative to substitute brain heart infusion medium. The effect of aeration and juice supplementation with yeast extract on the production of hyaluronic acid in batch fermentation was also investigated. Similar levels of cell mass were obtained in inoculum using cashew apple juice supplemented with yeast extract or the conventional brain heart infusion medium. Fermentation in Erlenmeyer flasks produced low biomass and hyaluronic acid concentrations. The hyaluronic acid concentration and viscosity increased from 0.15 g/L and 3.87 cP (no aeration or medium supplementation) to 1.76 g/L and 107 cP, when aeration (2 vvm) and 60 g/L of yeast extract were used. The results suggest the production of low-molecular weight hyaluronic acid oligomers instead of the high molecular weight polymer. PMID:24688498

Optimization of Energy Consumption and Mass Transfer Parameters in a Surface Aeration Vessel.

PubMed

Mohammadpour, A; AkhavanBehabadi, M A; Ebrahimzadeh, M; Raisee, M; MajdiNasab, A R; Nosrati, M; Mousavi, S M

2016-04-01

This paper reports tests on a lab-scale surface aeration vessel was equipped with a Rushton turbine to examine its performance in terms of standard aeration efficiency (SAE), mixing time, and void fraction characteristics. These characteristics were investigated by tests using variations of rotor speed, impeller immersion depth, and water level. Results showed that variation of impeller immersion depth had a greater effect on the SAE compared to variation of water level. Moreover, the SAE increased with rotor speeds up to about 150 to 200 rpm and then decreased. In addition, void fraction improved by impeller immersion depth and rotor speed enhancement; however, mixing time and power number were reduced as rotor speed increased. According to the response surface methodology statistical optimizations, optimum values for rotor speed, impeller immersion depth, and water level were 168.90 rpm, 25 mm, and 30 cm, respectively, to achieve the maximum value of SAE.

Numerical simulation for the air entrainment of aerated flow with an improved multiphase SPH model

NASA Astrophysics Data System (ADS)

Wan, Hang; Li, Ran; Pu, Xunchi; Zhang, Hongwei; Feng, Jingjie

2017-11-01

Aerated flow is a complex hydraulic phenomenon that exists widely in the field of environmental hydraulics. It is generally characterised by large deformation and violent fragmentation of the free surface. Compared to Euler methods (volume of fluid (VOF) method or rigid-lid hypothesis method), the existing single-phase Smooth Particle Hydrodynamics (SPH) method has performed well for solving particle motion. A lack of research on interphase interaction and air concentration, however, has affected the application of SPH model. In our study, an improved multiphase SPH model is presented to simulate aeration flows. A drag force was included in the momentum equation to ensure accuracy of the air particle slip velocity. Furthermore, a calculation method for air concentration is developed to analyse the air entrainment characteristics. Two studies were used to simulate the hydraulic and air entrainment characteristics. And, compared with the experimental results, the simulation results agree with the experimental results well.

Odorous gaseous emissions as influence by process condition for the forced aeration composting of pig slaughterhouse sludge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blazy, V., E-mail: vincent.blazy@irstea.fr; Guardia, A. de, E-mail: amaury.de-guardia@irstea.fr; Benoist, J.C

Highlights: • The gaseous emissions produced by various composting process conditions were characterized and quantified. • Nine compounds were potentially odorous: TMA, NH{sub 3}, 2-pentanone, 1-propanol-2-methyl, acetophenone and sulphur forms. • The tested composting process conditions reduced odour emissions by a factor of 5–10. • A reduction of 10{sup 5} to 10{sup 6} is required to reach an odour threshold limit at peak event emissions. • Both aeration rate and bulking agent had the most impact on reducing odour emissions. - Abstract: Compost sustainability requires a better control of its gaseous emissions responsible for several impacts including odours. Indeed, compostingmore » odours have stopped the operation of many platforms and prevented the installation of others. Accordingly, present technologies collecting and treating gases emitted from composting are not satisfactory and alternative solutions must be found. Thus, the aim of this paper was to study the influence of composting process conditions on gaseous emissions. Pig slaughterhouse sludge mixed with wood chips was composted under forced aeration in 300 L laboratory reactors. The process conditions studied were: aeration rate of 1.68, 4.03, 6.22, 9.80 and 13.44 L/h/kg of wet sludge; incorporation ratio of 0.55, 0.83 and 1.1 (kg of wet wood chips/kg of wet sludge), and; bulking agent particles size of <10, 10 < 20 and 20 < 30 mm. Out-going gases were sampled every 2 days and their composition was analysed using gas chromatography coupled with mass spectrometry (GC–MS). Fifty-nine compounds were identified and quantified. Dividing the cumulated mass production over 30 days of composting, by odour threshold, 9 compounds were identified as main potential odour contributors: hydrogen sulphide, trimethylamine, ammonia, 2-pentanone, 1-propanol-2-methyl, dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide and acetophenone. Five gaseous compounds were correlated with both aeration rate and bulking agent to waste ratio: hydrogen sulphide, trimethylamine, ammonia, 2-pentanone and 1-propanol-2-methyl. However, dropping the aeration rate and increasing the bulking agent to waste ratio reduced gaseous odour emissions by a factor of 5–10, when the required threshold dilution factor ranged from 10{sup 5} to 10{sup 6}, to avoid nuisance at peak emission rates. Process influence on emissions of dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide were poorly correlated with both aeration rate and bulking agent to waste ratio as a reaction with hydrogen sulphide was suspected. Acetophenone emissions originated from the wood chips. Olfactory measurements need to be correlated to gaseous emissions for a more accurate odour emission evaluation.« less

A Unique Autothermal Thermophilic Aerobic Digestion Process Showing a Dynamic Transition of Physicochemical and Bacterial Characteristics from the Mesophilic to the Thermophilic Phase.

PubMed

Tashiro, Yukihiro; Kanda, Kosuke; Asakura, Yuya; Kii, Toshihiko; Cheng, Huijun; Poudel, Pramod; Okugawa, Yuki; Tashiro, Kosuke; Sakai, Kenji

2018-03-15

A unique autothermal thermophilic aerobic digestion (ATAD) process has been used to convert human excreta to liquid fertilizer in Japan. This study investigated the changes in physicochemical and bacterial community characteristics during the full-scale ATAD process operated for approximately 3 weeks in 2 different years. After initiating simultaneous aeration and mixing using an air-inducing circulator (aerator), the temperature autothermally increased rapidly in the first 1 to 2 days with exhaustive oxygen consumption, leading to a drastic decrease and gradual increase in oxidation-reduction potential in the first 2 days, reached >50°C in the middle 4 to 6 days, and remained steady in the final phase. Volatile fatty acids were rapidly consumed and diminished in the first 2 days, whereas the ammonia nitrogen concentration was relatively stable during the process, despite a gradual pH increase to 9.3. Principal-coordinate analysis of 16S rRNA gene amplicons using next-generation sequencing divided the bacterial community structures into distinct clusters corresponding to three phases, and they were similar in the final phase in both years despite different transitions in the middle phase. The predominant phyla (closest species, dominancy) in the initial, middle, and final phases were Proteobacteria ( Arcobacter trophiarum , 19 to 43%; Acinetobacter towneri , 6.3 to 30%), Bacteroidetes ( Moheibacter sediminis , 43 to 54%), and Firmicutes ( Thermaerobacter composti , 11 to 28%; Heliorestis baculata , 2.1 to 16%), respectively. Two predominant operational taxonomic units (OTUs) in the final phase showed very low similarities to the closest species, indicating that the process is unique compared with previously published ones. This unique process with three distinctive phases would be caused by the aerator with complete aeration. IMPORTANCE Although the autothermal thermophilic aerobic digestion (ATAD) process has several advantages, such as a high degradation capacity, a short treatment period, and inactivation of pathogens, one of the factors limiting its broad application is the high electric power consumption for aerators with a full-scale bioreactor. We elucidated the dynamics of the bacterial community structures, as well as the physicochemical characteristics, in the ATAD process with a full-scale bioreactor from human excreta for 3 weeks. Our results indicated that this unique process can be divided into three distinguishable phases by an aerator with complete aeration and showed a possibility of shortening the digestion period to approximately 10 days. This research not only helps to identify which bacteria play significant roles and how the process can be improved and controlled but also demonstrates an efficient ATAD process with less electric power consumption for worldwide application. Copyright © 2018 American Society for Microbiology.

Stable isotope signatures for characterising the biological stability of landfilled municipal solid waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wimmer, Bernhard, E-mail: bernhard.wimmer@ait.ac.at; Hrad, Marlies; Huber-Humer, Marion

Highlights: ► The isotopic signature of δ{sup 13}C-DIC of leachates is linked to the reactivity of MSW. ► Isotopic signatures of leachates depend on aerobic/anaerobic conditions in landfills. ► In situ aeration of landfills can be monitored by isotope analysis in leachate. ► The isotopic analysis of leachates can be used for assessing the stability of MSW. ► δ{sup 13}C-DIC of leachates helps to define the duration of landfill aftercare. - Abstract: Stable isotopic signatures of landfill leachates are influenced by processes within municipal solid waste (MSW) landfills mainly depending on the aerobic/anaerobic phase of the landfill. We investigated themore » isotopic signatures of δ{sup 13}C, δ{sup 2}H and δ{sup 18}O of different leachates from lab-scale experiments, lysimeter experiments and a landfill under in situ aeration. In the laboratory, columns filled with MSW of different age and reactivity were percolated under aerobic and anaerobic conditions. In landfill simulation reactors, waste of a 25 year old landfill was kept under aerobic and anaerobic conditions. The lysimeter facility was filled with mechanically shredded fresh waste. After starting of the methane production the waste in the lysimeter containments was aerated in situ. Leachate and gas composition were monitored continuously. In addition the seepage water of an old landfill was collected and analysed periodically before and during an in situ aeration. We found significant differences in the δ{sup 13}C-value of the dissolved inorganic carbon (δ{sup 13}C-DIC) of the leachate between aerobic and anaerobic waste material. During aerobic degradation, the signature of δ{sup 13}C-DIC was mainly dependent on the isotopic composition of the organic matter in the waste, resulting in a δ{sup 13}C-DIC of −20‰ to −25‰. The production of methane under anaerobic conditions caused an increase in δ{sup 13}C-DIC up to values of +10‰ and higher depending on the actual reactivity of the MSW. During aeration of a landfill the aerobic degradation of the remaining organic matter caused a decrease to a δ{sup 13}C-DIC of about −20‰. Therefore carbon isotope analysis in leachates and groundwater can be used for tracing the oxidation–reduction status of MSW landfills. Our results indicate that monitoring of stable isotopic signatures of landfill leachates over a longer time period (e.g. during in situ aeration) is a powerful and cost-effective tool for characterising the biodegradability and stability of the organic matter in landfilled municipal solid waste and can be used for monitoring the progress of in situ aeration.« less

Organics removal from landfill leachate and activated sludge production in SBR reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klimiuk, Ewa; Kulikowska, Dorota

2006-07-01

This study is aimed at estimating organic compounds removal and sludge production in SBR during treatment of landfill leachate. Four series were performed. At each series, experiments were carried out at the hydraulic retention time (HRT) of 12, 6, 3 and 2 d. The series varied in SBR filling strategies, duration of the mixing and aeration phases, and the sludge age. In series 1 and 2 (a short filling period, mixing and aeration phases in the operating cycle), the relationship between organics concentration (COD) in the leachate treated and HRT was pseudo-first-order kinetics. In series 3 (with mixing and aerationmore » phases) and series 4 (only aeration phase) with leachate supplied by means of a peristaltic pump for 4 h of the cycle (filling during reaction period) - this relationship was zero-order kinetics. Activated sludge production expressed as the observed coefficient of biomass production (Y {sub obs}) decreased correspondingly with increasing HRT. The smallest differences between reactors were observed in series 3 in which Y {sub obs} was almost stable (0.55-0.6 mg VSS/mg COD). The elimination of the mixing phase in the cycle (series 4) caused the Y {sub obs} to decrease significantly from 0.32 mg VSS/mg COD at HRT 2 d to 0.04 mg VSS/mg COD at HRT 12 d. The theoretical yield coefficient Y accounted for 0.534 mg VSS/mg COD (series 1) and 0.583 mg VSS/mg COD (series 2). In series 3 and 4, it was almost stable (0.628 mg VSS/mg COD and 0.616 mg VSS/mg COD, respectively). After the elimination of the mixing phase in the operating cycle, the specific biomass decay rate increased from 0.006 d{sup -1} (series 3) to 0.032 d{sup -1} (series 4). The operating conditions employing mixing/aeration or only aeration phases enable regulation of the sludge production. The SBRs operated under aerobic conditions are more favourable at a short hydraulic retention time. At long hydraulic retention time, it can lead to a decrease in biomass concentration in the SBR as a result of cell decay. On the contrary, in the activated sludge at long HRT, a short filling period and operating cycle of the reactor with the mixing and aeration phases seem the most favourable.« less

Record rates of pressurized gas-flow in the great horsetail, Equisetum telmateia. Were Carboniferous Calamites similarly aerated?

PubMed

Armstrong, Jean; Armstrong, William

2009-01-01

Significant pressurized (convective) ventilation has been demonstrated in some flowering wetland plants, for example water-lilies and reeds, but not previously in nonflowering plants. Here we investigated convective flows in the great horsetail, Equisetum telmateia, and the possibility that convections aerated the massive rhizomes of the Calamites, extinct giant horsetails of the Carboniferous. Convection in E. telmateia was examined in relation to induction sites, anatomical pathways, relative humidity (RH), external wind-speed, diurnal effects, rhizome resistance and pressure-gradients. A mathematical model, incorporating Calamite aeration anatomy, was applied in assessing potentials for convective aeration. Individual shoots of E. telmateia generated extremely high rates of humidity-induced convection: < or = 120 cm(3) min(-1) (internal wind-velocity: 10 cm s(-1)) with rates proportional to branch numbers and 1/RH. Flows passed through branches, stem and rhizome via low-resistance lacunae (vallecular canals) and vented via stubble. Stomata supported internal pressures up to 800 Pa. Anatomically, E. telmateia resembles the Calamites and modelling predicted possible flows of 70 l min(-1) per Calamite tree. This is the first demonstration of significant convective flow in a nonflowering species, indicating that plant ventilation by a type of 'molecular gas-pump' may date back 350 million yr or more. Stomatal form and low-resistance pathways may facilitate high flow rates.

Modular operation of membrane bioreactors for higher hydraulic capacity utilisation.

PubMed

Veltmann, K; Palmowski, L M; Pinnekamp, J

2011-01-01

Using data from 6 full-scale municipal membrane bioreactors (MBR) in Germany the hydraulic capacity utilisation and specific energy consumption were studied and their connexion shown. The average hydraulic capacity utilisation lies between 14% and 45%. These low values are justified by the necessity to deal with intense rain events and cater for future flow increases. However, this low hydraulic capacity utilisation leads to high specific energy consumption. The optimisation of MBR operation requires a better utilisation of MBR hydraulic capacity, particularly under consideration of the energy-intensive membrane aeration. A first approach to respond to large influent flow fluctuations consists in adjusting the number of operating modules. This is practised by most MBR operators but so far mostly with variable flux and constant membrane aeration. A second approach is the real-time adjustment of membrane aeration in line with flux variations. This adjustment is not permitted under current manufacturers' warranty conditions. A further opportunity is a discontinuous operation, in which filtration takes place over short periods at high flux and energy for membrane aeration is saved during filtration pauses. The integration of a buffer volume is thereby indispensable. Overall a modular design with small units, which can be activated/ inactivated according to the influent flow and always operate under optimum conditions, enables a better utilisation of MBR hydraulic capacity and forms a solid base to reduce MBR energy demand.

The Device Design of a Rural Domestic Sewage Treatment Performance

NASA Astrophysics Data System (ADS)

Liu, Zuhan; Wang, Lili; Deng, Chengzhi

2017-10-01

A kind of device for removing pollutant from rural domestic sewage isstudied in this paper, which belongs to the field of sewage treatment technology. The device include anaerobic pool, aerobiotic pool and aerating apparatus. Specifically, the aerobiotic pool is a sealed rectangular body with a rectangular groove on its top cover. The fixed wall is established on one side of the rectangular groove, and the wall is located in the middle of the top cover. The anaerobic pool is opposite to the fixed wall. And there is a aerating apparatusbetween the anaerobic pool and fixed wall, and the apparatus is situated right above the rectangular groove. The design is simple in structure and low in manufacturing cost. The biochemical ratio to the sewage could be improved through the anaerobic pool, and then the sewage is sufficiently aerated by means of natural ventilation and height of water. Theaerated sewage enter into aerobiotic pool, and then the organic matter is degraded into Carbon Dioxide and water under the action of aerobic bacteria, of which function is that the ammonia nitrogen is oxidized into nitrate and nitrite. The water that is far from the aerating apparatus inside of the aerobiotic pool enters into oxygen-deficient environment, and the nitrate is converted into nitrogen. After the effluent is checked qualified, the water is discharged into the drainage ditch or utilized for irrigation.

Relationship between respiratory quotient, nitrification, and nitrous oxide emissions in a forced aerated composting process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsutsui, Hirofumi, E-mail: jm-tsutsuih@kochi-u.ac.jp; Japan Science and Technology Agency, CREST; Fujiwara, Taku

2015-08-15

Highlights: • RQ can be an indicator of N{sub 2}O emission in forced aerated composting process. • Emission of N{sub 2}O with nitrification was observed with RQ decrease. • Mass balances demonstrated the RQ decrease was caused by nitrification. • Conversion ratio of oxidized ammonia and total N to N{sub 2}O were ∼2.7%. - Abstract: We assessed the relationship between respiratory quotient (RQ) and nitrification and nitrous oxide (N{sub 2}O) emission in forced aerated composting using lab-scale reactors. Relatively high RQ values from degradation of readily degradable organics initially occurred. RQ then stabilized at slightly lower values, then decreased. Continuousmore » emission of N{sub 2}O was observed during the RQ decrease. Correlation between nitrification and N{sub 2}O emission shows that the latter was triggered by nitrification. Mass balances demonstrated that the O{sub 2} consumption of nitrification (∼24.8 mmol) was slightly higher than that of CO{sub 2} emission (∼20.0 mmol), indicating that the RQ decrease was caused by the occurrence of nitrification. Results indicate that RQ is a useful index, which not only reflects the bioavailability of organics but also predicts the occurrence of nitrification and N{sub 2}O emission in forced aerated composting.« less

Economic evaluation of alternative wastewater treatment plant options for pulp and paper industry.

PubMed

Buyukkamaci, Nurdan; Koken, Emre

2010-11-15

Excessive water consumption in pulp and paper industry results in high amount of wastewater. Pollutant characteristics of the wastewater vary depending on the processes used in production and the quality of paper produced. However, in general, high organic material and suspended solid contents are considered as major pollutants of pulp and paper industry effluents. The major pollutant characteristics of pulp and paper industry effluents in Turkey were surveyed and means of major pollutant concentrations, which were grouped in three different pollution grades (low, moderate and high strength effluents), and flow rates within 3000 to 10,000m(3)/day range with 1000m(3)/day steps were used as design parameters. Ninety-six treatment plants were designed using twelve flow schemes which were combinations of physical treatment, chemical treatment, aerobic and anaerobic biological processes. Detailed comparative cost analysis which includes investment, operation, maintenance and rehabilitation costs was prepared to determine optimum treatment processes for each pollution grade. The most economic and technically optimal treatment processes were found as extended aeration activated sludge process for low strength effluents, extended aeration activated sludge process or UASB followed by an aeration basin for medium strength effluents, and UASB followed by an aeration basin or UASB followed by the conventional activated sludge process for high strength effluents. Copyright © 2010 Elsevier B.V. All rights reserved.

Effects of step-feeding and intermittent aeration on organics and nitrogen removal in a horizontal subsurface flow constructed wetland.

PubMed

Patil, Sagar; Chakraborty, Saswati

2017-03-21

The effect of step feed strategy and intermittent aeration on removal of chemical oxygen demand (COD) and nitrogen was investigated in a laboratory scale horizontal subsurface flow constructed wetland (HSSFCW). Wetland was divided into four zones along the length (zone I to IV), and influent was introduced into first and third zones by step feeding. Continuous study was carried out in four phases. In phases I to III, 30% of influent was bypassed to zone III for denitrification along with organics removal. Intermittent aeration was provided only in zone II at 2.5 L/min for 4 h/day, during phases II, III and IV. In phase I, 87% COD and 43% NH 4 + -N (ammonia-nitrogen) removal were obtained from influents of 331 and 30 mg/L, respectively. In phase II study, external aeration resulted in 97% COD and 71% NH 4 + -N removal in the wetland. In phase IV, 40% of feed was delivered to zone III. Higher supply of organic in zone III resulted in higher denitrification, and total nitrogen removal rate increased to 70% from 56%. In the final effluent, concentration of NO 3 - -N was 9-11 mg/L in phase I to III and decreased to 4 mg/L in phase IV. Batch study showed that COD and NH 4 + -N removal followed first order kinetics in different zones of wetland.

Application of Oxygen-Enriched Aeration in the Production of Bacitracin by Bacillus licheniformis

PubMed Central

Flickinger, M. C.; Perlman, D.

1979-01-01

The physiological effects of controlling the dissolved oxygen tension at 0.01, 0.02, and 0.05 atm by the use of oxygen-enriched aeration were investigated during growth and bacitracin production by Bacillus licheniformis ATCC 10716. Up to a 2.35-fold increase in the final antibiotic yield and a 4-fold increase in the rate of bacitracin synthesis were observed in response to O2-enriched aeration. The increase in antibiotic production was accompanied by increased respiratory activity and an increase in the specific productivity of the culture from 1.3 to 3.6 g of antibiotic per g of cell mass produced. Oxygen enrichment of the aeration decreased medium carbohydrate uptake and the maximum specific growth rate of B. licheniformis from 0.6 h−1 to as low as 0.15 h−1, depending upon the level of enrichment and the conditions of oxygen transfer rate (impeller speed). The response of this culture to O2 enrichment suggests that this method of controlling the dissolved oxygen tension for antibiotic-producing cultures may simulate conditions that would occur if the carbon source were fed slowly, as is often employed to optimize antibiotic production. Analysis of the biologically active bacitracins produced by B. licheniformis ATCC 10716 suggested that the ratio of biologically active peptides was not changed by O2 enrichment, nor were any new biologically active compounds formed. Images PMID:34361

Treatability of volatile chlorinated hydrocarbon-contaminated soils of different textures along a vertical profile by mechanical soil aeration: A laboratory test.

PubMed

Ma, Yan; Shi, Yi; Hou, Deyi; Zhang, Xi; Chen, Jiaqi; Wang, Zhifen; Xu, Zhu; Li, Fasheng; Du, Xiaoming

2017-04-01

Mechanical soil aeration is a simple, effective, and low-cost soil remediation technology that is suitable for sites contaminated with volatile chlorinated hydrocarbons (VCHs). Conventionally, this technique is used to treat the mixed soil of a site without considering the diversity and treatability of different soils within the site. A laboratory test was conducted to evaluate the effectiveness of mechanical soil aeration for remediating soils of different textures (silty, clayey, and sandy soils) along a vertical profile at an abandoned chloro-alkali chemical site in China. The collected soils were artificially contaminated with chloroform (TCM) and trichloroethylene (TCE). Mechanical soil aeration was effective for remediating VCHs (removal efficiency >98%). The volatilization process was described by an exponential kinetic function. In the early stage of treatment (0-7hr), rapid contaminant volatilization followed a pseudo-first order kinetic model. VCH concentrations decreased to low levels and showed a tailing phenomenon with very slow contaminant release after 8hr. Compared with silty and sandy soils, clayey soil has high organic-matter content, a large specific surface area, a high clay fraction, and a complex pore structure. These characteristics substantially influenced the removal process, making it less efficient, more time consuming, and consequently more expensive. Our findings provide a potential basis for optimizing soil remediation strategy in a cost-effective manner. Copyright © 2016. Published by Elsevier B.V.

Preliminary Investigation of the Corrosion Behavior of Proprietary Micro-alloyed Steels in Aerated and Deaerated Brine Solutions

NASA Astrophysics Data System (ADS)

Onyeji, Lawrence; Kale, Girish

2017-12-01

The corrosion performance of fairly new generation of micro-alloyed steels was compared in different concentrations of aerated and deaerated brines. Electrochemical polarization, weight loss and surface analyses techniques were employed. The results showed a threshold of corrosion rate at 3.5 wt.% NaCl in both aerated and deaerated solutions. The average corrosion current density for steel B, for example, increased from 1.3 µA cm-2 in 1 wt.% NaCl to 1.5 µA cm-2 in 3.5 wt.% NaCl, but decreased to 1.4 µA cm-2 in 10 wt.% deaerated NaCl solutions. The aerated solutions exhibited an average of over 80% increase in corrosion current density in the respective concentrations when compared with the deaerated solution. These results can be attributed to the effects of dissolved oxygen (DO) which has a maximum solubility in 3.5 wt.% NaCl. DO as a depolarizer and electron acceptor in cathodic reactions accelerates anodic metal dissolution. The difference in carbon content and microstructures occasioned by thermo-mechanical treatment contributed to the witnessed variation in corrosion performance of the steels. Specifically, the results of the various corrosion techniques corroborated each other and showed that the corrosion rate of the micro-alloyed steels can be ranked as CRSteel A < CRX65 < CRSteel B < CRSteel C.

Improving performance of MFC by design alteration and adding cathodic electrolytes.

PubMed

Jadhav, G S; Ghangrekar, M M

2008-12-01

Performance of two microbial fuel cells (MFCs) was investigated under batch and continuous mode of operation using different cathodic electrolyte. The wastewater was supplied from the bottom port provided to the anode chamber in both the MFCs and the effluent left the anode chamber from the top port in MFC-1, whereas in MFC-2, the effluent exit was provided close to membrane. Stainless steel (SS) mesh anode was used in both the MFCs with surface area of 167 and 100 cm(2) in MFC-1 and MFC-2, respectively. Under batch mode and continuous mode of operation, these MFCs gave chemical oxygen demand removal efficiency more than 85% and about 68%, respectively. Under batch mode of operation, maximum power density of 39.95 and 56.87 mW/m(2) and maximum current density of 180.83 and 295 mA/m(2) were obtained in MFC-1 and MFC-2, respectively. Under continuous mode of operation, a reduction in power and current density was observed. Even with less surface area of the anode, MFC-2 produced more current (1.77 mA) than MFC-1 (1.40 mA). Among the cathodic electrolyte tested, these can be listed in decreasing order of power density as aerated KMnO(4) solution > KMnO(4) solution without aeration > aerated tap water > aerated tap water with NaCl.

Treatment of wastewater from a school in a decentralized filtration system by percolation over organic packing media.

PubMed

Garzón-Zúñiga, M A; Buelna, G

2011-01-01

Based on results obtained in the laboratory a WWTP composed of a septic tank and an aerated percolating filter packed with organic media was built for a school. The system can treat 18 m3 d(-1) and was operated with a hydraulic loading rate of 0.078 (m3 m(-2) d(-1). For 360 days different operational conditions including start-up; stabilization; operation with aeration and non aeration; effect of rainy season, breaks from activities due to holidays and restart; were monitored and described in the article. Once stabilized, the system was able to remove, without the need for mechanical aeration, 97% of BOD5, 71% of COD, 93% of TKN, 11% of PO(4-)-P, 95% of TSS, 96% of VSS, in addition to having a removal efficiency of 4 log units of Faecal Coliforms (FC) and 100% helminthes eggs (HE). With this quality, the treated wastewater can be chlorinated and reused to irrigate green areas and/or in toilets. Although sanitary wastewater has a high concentration of Total-N (250 mg L(-1)) and a C/N ratio of less than 1, the system removed 65% of Total-N. Finally it was observed that after non activity periods, there was neither system failure nor the need to re-stabilize the system.

Sterilization of medical devices by ethylene oxide, determination of the dissipation of residues, and use of Green Fluorescent Protein as an indicator of process control.

PubMed

Dias, Fábio N; Ishii, Marina; Nogaroto, Sergio L; Piccini, Bruno; Penna, Thereza C V

2009-11-01

Ethylene oxide (EO) is used to sterilize Oxygenator and Tubing applied to heart surgery. Residual levels of EO and its derivatives, ethylene chlorohydrin (ECH) and ethylene glycol (EG), may be hazardous to the patients. Therefore, it must be removed by the aeration process. This study aimed to estimate the minimum aeration time for these devices to attain safe limits for use (avoiding excessive aeration time) and to evaluate the Green Fluorescent Protein (GFP) as a biosensor capable of best indicating the distribution and penetration of EO gas throughout the sterilization chamber. Sterilization cycles of 2, 4, and 8 h were monitored by Bacillus atrophaeus ATCC 9372 as a biological indicator (BI) and by the GFP. Residual levels of EO, ECH, and EG were determined by gas chromatography (GC), and the residual dissipation was studied. Safe limits were reached right after the sterilization process for Oxygenator and after 204 h of aeration for Tubing. In the 2 h cycle, the GFP concentration decreased from 4.8 (+/-3.2)% to 7.5 (+/-2.5)%. For the 4 h cycle, the GFP concentration decreased from 17.4 (+/-3.0)% to 21.5 (+/-6.8)%, and in the 8 h cycle, it decreased from 22.5 (+/-3.2)% to 23.9 (+/-3.9)%. This finding showed the potentiality for GFP applications as an EO biosensor.

Clownfish in hypoxic anemones replenish host O2 at only localised scales.

PubMed

Herbert, N A; Bröhl, S; Springer, K; Kunzmann, A

2017-07-26

The clownfish-anemone association exemplifies a symbiosis where both members benefit from nutrient exchange and protection from predators. Clownfish also perform aeration-like behaviour in their host anemones at night, but it is not yet known whether this is stimulated by the onset of hypoxia, and whether both members benefit from O 2 replenishment. Oxygen at 3 distances above the sea anemone Entacmaea quadricolor (0.2, 1.2 and 2.2 cm) therefore was measured under 3 light levels (photon flux density = 0, 55 and 110 µmol m -2 s -1 ), with and without the anemonefish Amphiprion frenatus. Hypoxia (O 2  < 50% air saturation) was recorded in the anemone, but only at 0.2 cm away from the anemone surface under dark conditions when A. frenatus was absent. This localised layer of hypoxia was eliminated by the presence of A. frenatus exhibiting aeration-like behaviour. Respirometry revealed that A. frenatus is extremely hypoxia tolerant (S crit  = 14.3% at 25 °C), suggesting that aeration behaviour does not provide a major metabolic advantage to clownfish because they do not breathe water at 0.2 cm and are not metabolically constrained by O 2 at distances ≥ 1.2 cm. That the aeration behaviour of A. frenatus facilitates only the metabolism of its O 2 -conforming host reveals a unique aspect of this symbiotic relationship.

Thermophilic aeration of cattle slurry with whey and/or jam wastes.

PubMed

Heinonen-Tanski, Helvi; Kiuru, Tapio; Ruuskanen, Juhani; Korhonen, Kari; Koivunen, Jari; Ruokojärvi, Arja

2005-01-01

Thermophilic aeration of cattle slurry and food industrial by-products was studied with the aim to improve hygienic qualities of the slurry so that it could be used as a safe fertiliser for berries to be eaten raw. We also wanted to study if the process would be energetically favourable in an arctic climate. Cattle slurry alone or with whey and/or jam waste was treated. The tests were done in a well heat-insulated reactor with a 10 m(3) volume. Temperature increases up to over 70 degrees C could be recorded in 19 days even though some processes were carried out in winter time when the ambient air temperature was less than 0 degrees C. The heat energy formed was higher than the electrical energy needed to carry out the aeration. The hygienic qualities of the aerated product were good with only minor nitrogen losses. The end product could be useful as a fertiliser and soil improving compound to increase the organic matter content of agricultural soil. Cattle slurry alone was well suited as the raw material if attaining a high temperature was the main goal. A part of slurry could be replaced with food-industrial side products. Whey waste suited better for co-composting than jam waste but the mixture of whey, jam waste, and slurry was optimal for composting.

Selection of non-Saccharomyces yeast strains for reducing alcohol levels in wine by sugar respiration.

PubMed

Quirós, Manuel; Rojas, Virginia; Gonzalez, Ramon; Morales, Pilar

2014-07-02

Respiration of sugars by non-Saccharomyces yeasts has been recently proposed for lowering alcohol levels in wine. Development of industrial fermentation processes based on such an approach requires, amongst other steps, the identification of yeast strains which are able to grow and respire under the relatively harsh conditions found in grape must. This work describes the characterization of a collection of non-Saccharomyces yeast strains in order to identify candidate yeast strains for this specific application. It involved the estimation of respiratory quotient (RQ) values under aerated conditions, at low pH and high sugar concentrations, calculation of yields of ethanol and other relevant metabolites, and characterization of growth responses to the main stress factors found during the first stages of alcoholic fermentation. Physiological features of some strains of Metschnikowia pulcherrima or two species of Kluyveromyces, suggest they are suitable for lowering ethanol yields by respiration. The unsuitability of Saccharomyces cerevisiae strains for this purpose was not due to ethanol yields (under aerated conditions they are low enough for a significant reduction in final ethanol content), but to the high acetic acid yields under these growth conditions. According to results from controlled aeration fermentations with one strain of M. pulcherrima, design of an aeration regime allowing for lowering ethanol yields though preserving grape must components from excessive oxidation, would be conceivable. Copyright © 2014. Published by Elsevier B.V.

Effect of dilution rate and nutrients addition on the fermentative capability and synthesis of aromatic compounds of two indigenous strains of Saccharomyces cerevisiae in continuous cultures fed with Agave tequilana juice.

PubMed

Morán-Marroquín, G A; Córdova, J; Valle-Rodríguez, J O; Estarrón-Espinosa, M; Díaz-Montaño, D M

2011-11-15

Knowledge of physiological behavior of indigenous tequila yeast used in fermentation process is still limited. Yeasts have significant impact on the productivity fermentation process as well as the sensorial characteristics of the alcoholic beverage. For these reasons a better knowledge of the physiological and metabolic features of these yeasts is required. The effects of dilution rate, nitrogen and phosphorus source addition and micro-aeration on growth, fermentation and synthesis of volatile compounds of two native Saccharomyces cerevisiae strains, cultured in continuous fed with Agave tequilana juice were studied. For S1 and S2 strains, maximal concentrations of biomass, ethanol, consumed sugars, alcohols and esters were obtained at 0.04 h⁻¹. Those concentrations quickly decreased as D increased. For S. cerevisiae S1 cultures (at D=0.08 h⁻¹) supplemented with ammonium phosphate (AP) from 1 to 4 g/L, concentrations of residual sugars decreased from 29.42 to 17.60 g/L and ethanol increased from 29.63 to 40.08 g/L, respectively. The S1 culture supplemented with AP was then micro-aerated from 0 to 0.02 vvm, improving all the kinetics parameters: biomass, ethanol and glycerol concentrations increased from 5.66, 40.08 and 3.11 g/L to 8.04, 45.91 and 4.88 g/L; residual sugars decreased from 17.67 g/L to 4.48 g/L; and rates of productions of biomass and ethanol, and consumption of sugars increased from 0.45, 3.21 and 7.33 g/L·h to 0.64, 3.67 and 8.38 g/L·h, respectively. Concentrations of volatile compounds were also influenced by the micro-aeration rate. Ester and alcohol concentrations were higher, in none aerated and in aerated cultures respectively. Copyright © 2011. Published by Elsevier B.V.

Subsurface flow and vegetation patterns in tidal environments

NASA Astrophysics Data System (ADS)

Ursino, Nadia; Silvestri, Sonia; Marani, Marco

2004-05-01

Tidal environments are characterized by a complex interplay of hydrological, geomorphic, and biological processes, and their understanding and modeling thus require the explicit description of both their biotic and abiotic components. In particular, the presence and spatial distribution of salt marsh vegetation (a key factor in the stabilization of the surface soil) have been suggested to be related to topographic factors and to soil moisture patterns, but a general, process-based comprehension of this relationship has not yet been achieved. The present paper describes a finite element model of saturated-unsaturated subsurface flow in a schematic salt marsh, driven by tidal fluctuations and evapotranspiration. The conditions leading to the establishment of preferentially aerated subsurface zones are studied, and inferences regarding the development and spatial distribution of salt marsh vegetation are drawn, with important implications for the overall ecogeomorphological dynamics of tidal environments. Our results show that subsurface water flow in the marsh induces complex water table dynamics, even when the tidal forcing has a simple sinusoidal form. The definition of a space-dependent aeration time is then proposed to characterize root aeration. The model shows that salt marsh subsurface flow depends on the distance from the nearest creek or channel and that the subsurface water movement near tidal creeks is both vertical and horizontal, while farther from creeks, it is primarily vertical. Moreover, the study shows that if the soil saturated conductivity is relatively low (10-6 m s-1, values quite common in salt marsh areas), a persistently unsaturated zone is present below the soil surface even after the tide has flooded the marsh; this provides evidence of the presence of an aerated layer allowing a prolonged presence of oxygen for aerobic root respiration. The results further show that plant transpiration increases the extent and persistence of the aerated layer, thereby introducing a strong positive feedback: Pioneer plants on marsh edges have the effect of increasing soil oxygen availability, thus creating the conditions for the further development of other plant communities.

Successful aerobic bioremediation of groundwater contaminated with higher chlorinated phenols by indigenous degrader bacteria.

PubMed

Mikkonen, Anu; Yläranta, Kati; Tiirola, Marja; Dutra, Lara Ambrosio Leal; Salmi, Pauliina; Romantschuk, Martin; Copley, Shelley; Ikäheimo, Jukka; Sinkkonen, Aki

2018-07-01

The xenobiotic priority pollutant pentachlorophenol has been used as a timber preservative in a polychlorophenol bulk synthesis product containing also tetrachlorophenol and trichlorophenol. Highly soluble chlorophenol salts have leaked into groundwater, causing severe contamination of large aquifers. Natural attenuation of higher-chlorinated phenols (HCPs: pentachlorophenol + tetrachlorophenol) at historically polluted sites has been inefficient, but a 4-year full scale in situ biostimulation of a chlorophenol-contaminated aquifer by circulation and re-infiltration of aerated groundwater was remarkably successful: pentachlorophenol decreased from 400 μg L -1 to <1 μg L -1 and tetrachlorophenols from 4000 μg L -1 to <10 μg L -1 . The pcpB gene, the gene encoding pentachlorophenol hydroxylase - the first and rate-limiting enzyme in the only fully characterised aerobic HCP degradation pathway - was present in up to 10% of the indigenous bacteria already 4 months after the start of aeration. The novel quantitative PCR assay detected the pcpB gene in situ also in the chlorophenol plume of another historically polluted aquifer with no remediation history. Hotspot groundwater HCPs from this site were degraded efficiently during a 3-week microcosm incubation with one-time aeration but no other additives: from 5400 μg L -1 to 1200 μg L -1 and to 200 μg L -1 in lightly and fully aerated microcosms, respectively, coupled with up to 2400% enrichment of the pcpB gene. Accumulation of lower-chlorinated metabolites was observed in neither in situ remediation nor microcosms, supporting the assumption that HCP removal was due to the aerobic degradation pathway where the first step limits the mineralisation rate. Our results demonstrate that bacteria capable of aerobic mineralisation of xenobiotic pentachlorophenol and tetrachlorophenol can be present at long-term polluted groundwater sites, making bioremediation by simple aeration a viable and economically attractive alternative. Copyright © 2018 Elsevier Ltd. All rights reserved.

User preferences and water use savings owing to washbasin taps retrofit: a case study of the DECivil building of the University of Aveiro.

PubMed

Meireles, Inês; Sousa, Vítor; Adeyeye, Kemi; Silva-Afonso, Armando

2017-04-04

During the last decades, achieving water efficiency in buildings has increasingly become an important challenge in the scope of sustainability. Water consumption is directly related to individual conduct. Despite the various technological improvements in fixtures and appliances, their performance will be influenced by human preferences and behavior. As a result, the potential for effective water consumption saving is influenced by behavior change as well as water-efficient fixtures and appliances. This work evaluates the impact of user preferences and behavior change on the water-efficient performance of tap aerators in a case study building: the Department of Civil Engineering building of the University of Aveiro, Portugal. Four aerators with different discharge reductions and types were installed in the toilet's washbasins and the user's preferences and behavior change measured through direct and online questionnaires. It was observed that the effective water consumption reduction (15 to 49%) was less than the discharge reduction (30 to 70%), confirming that user factors influence water savings. Water use reductions in the tested range (2.0 to 6.7 l/min) also varied according to gender, with male users using less water than their female counterparts. It was noted that an awareness of sustainability values prevailed amongst the users when confronted with the choice between comfort and water efficiency, although differences were observed in the user preferences regarding the various aerators. When confronted with the information that the lower discharge aerator would contribute to a reduction of about 70% on the water discharge, 25% of the users agreed with its use, even if it resulted in a certain degree of dissatisfaction. In comparison, only 8% of the users completely disagreed with its installation. On average, the water consumption reduction was 46% smaller than the discharge reduction achievable with the aerator alone. This further confirms the user factors inform the degree of water savings that is achievable from water-efficient fittings and fixtures.

Alternating anoxic feast/aerobic famine condition for improving granular sludge formation in sequencing batch airlift reactor at reduced aeration rate.

PubMed

Wan, Junfeng; Bessière, Yolaine; Spérandio, Mathieu

2009-12-01

In this study the influence of a pre-anoxic feast period on granular sludge formation in a sequencing batch airlift reactor is evaluated. Whereas a purely aerobic SBR was operated as a reference (reactor R2), another reactor (R1) was run with a reduced aeration rate and an alternating anoxic-aerobic cycle reinforced by nitrate feeding. The presence of pre-anoxic phase clearly improved the densification of aggregates and allowed granular sludge formation at reduced air flow rate (superficial air velocity (SAV)=0.63cms(-1)). A low sludge volume index (SVI(30)=45mLg(-1)) and a high MLSS concentration (9-10gL(-1)) were obtained in the anoxic/aerobic system compared to more conventional results for the aerobic reactor. A granular sludge was observed in the anoxic/aerobic system whilst only flocs were observed in the aerobic reference even when operated at a high aeration rate (SAV=2.83cms(-1)). Nitrification was maintained efficiently in the anoxic/aerobic system even when organic loading rate (OLR) was increased up to 2.8kgCODm(-3)d(-1). In the contrary nitrification was unstable in the aerobic system and dropped at high OLR due to competition between autotrophic and heterotrophic growth. The presence of a pre-anoxic period positively affected granulation process via different mechanisms: enhancing heterotrophic growth/storage deeper in the internal anoxic layer of granule, reducing the competition between autotrophic and heterotrophic growth. These processes help to develop dense granular sludge at a moderate aeration rate. This tends to confirm that oxygen transfer is the most limiting factor for granulation at reduced aeration. Hence the use of an alternative electron acceptor (nitrate or nitrite) should be encouraged during feast period for reducing energy demand of the granular sludge process.

Bacterial aerosol emission rates from municipal wastewater aeration tanks.

PubMed Central

Sawyer, B; Elenbogen, G; Rao, K C; O'Brien, P; Zenz, D R; Lue-Hing, C

1993-01-01

In this report we describe the results of a study conducted to determine the rates of bacterial aerosol emission from the surfaces of the aeration tanks of the Metropolitan Water Reclamation District of Greater Chicago John E. Egan Water Reclamation Plant. This study was accomplished by conducting test runs in which Andersen six-stage viable samplers were used to collect bacterial aerosol samples inside a walled tower positioned above an aeration tank liquid surface at the John E. Egan Water Reclamation Plant. The samples were analyzed for standard plate counts (SPC), total coliforms (TC), fecal coliforms, and fecal streptococci. Two methods of calculation were used to estimate the bacterial emission rate. The first method was a conventional stack emission rate calculation method in which the measured air concentration of bacteria was multiplied by the air flow rate emanating from the aeration tanks. The second method was a more empirical method in which an attempt was made to measure all of the bacteria emanating from an isolated area (0.37 m2) of the aeration tank surface over time. The data from six test runs were used to determine bacterial emission rates by both calculation methods. As determined by the conventional calculation method, the average SPC emission rate was 1.61 SPC/m2/s (range, 0.66 to 2.65 SPC/m2/s). As determined by the empirical calculation method, the average SPC emission rate was 2.18 SPC/m2/s (range, 1.25 to 2.66 SPC/m2/s). For TC, the average emission rate was 0.20 TC/m2/s (range, 0.02 to 0.40 TC/m2/s) when the conventional calculation method was used and 0.27 TC/m2/s (range, 0.04 to 0.53 TC/m2/s) when the empirical calculation method was used.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8250547

Sediment-Overlying Water Relationships Affecting Wintertime Dissolved Oxygen Conditions in the Big Eau Pleine Reservoir, Wisconsin.

DTIC Science & Technology

1992-07-01

22202-4302. and to the Office of Managel ent and Bidget . P worki Reduction Pfo4ect(07T4-016 Wahington. DC 20S03. -1. AGENCY USE ONLY (Leave blank) 2...higher pool elevation can not be maintained, it is likely that additional aerators must be installed for incremental use to meet periodic heavy oxygen...install additional aerators throughout the reservoir for incremental use as needed to enhance oxygen diffusion processes. The difficulty with this

Evaluation of Koontz Lake (North Indiana) Ecological Restoration Options - Comparison of Dredging and Aeration - and Broad Application to USACE Projects

DTIC Science & Technology

2018-01-01

Restoration Options – Comparison of Dredging and Aeration – and Broad Application to USACE Projects En vi ro nm en ta l L ab or at or y Victor F. Medina... Projects Victor F. Medina, Kaytee Pokrzywinski, and Edith Martinez-Guerra Environmental Laboratory U.S. Army Engineer Research and Development...Operations Technical Support Program 3909 Halls Ferry Road Vicksburg, MS 39180 Under Project No. TA2017-002, “Evaluation of Koontz Lake (Indiana

Solar-energy mobile water aerators are efficient for restoring eutrophic water

NASA Astrophysics Data System (ADS)

Wang, Y. Y.; Xu, Z. X.

2017-01-01

Surface water eutrophication has become a worldwide social issue. large amounts of secondhand energy, high capital investment are required, and most ecosystem disturbances will arise in the conventional eutrophication restoration measures. However, mobile solar-energy water aerator has the better oxygen transfer rate, hydrodynamic condition and can be used in the large waterbody for its cruising character. Second, the device is low carbon and sustainable for the solar photovoltaic system applications. So the device can be widely used in the eutrophication restoration.

Fecal-coliform bacteria in extended-aeration plant sludge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, M.; Kester, G.; Arant, S.

1998-07-01

The concentration of fecal-coliform bacteria in sludge from extended-aeration plants was analyzed for compliance with new state and federal land application requirements. This study was initiated to determine if additional digestion would be necessary for plants to meet the new pathogen standards of less than 2 million CFU per gm of solids. Sludge was found to contain less than 2 million fecal coliform bacteria/gm of sludge as a result of a combination or aerobic digestion and/or long term storage.

Tertiary Treatment of Wastewater Using a Rotating Biological Contactor System.

DTIC Science & Technology

1980-02-01

in deter- gal/sq ft/day (0.04 m3 /m 2 /day) could remove BOD mining nitrification efficiency (temperature steady at from winery wastes at an efficiency...and J. E. Tehan, "Treatment of 210. Hao and G. F. Hendricks. "Rotating Biological Reactors Winery Wastes by Aerated Lagoon. Activated Sludge, and...Pollution Control Federa- tion, January 1978). LaBella. S. A.. I. H. Thaker, and J. E. Tehan. "Treatment of Winery Wastes by Aerated Lagoon. Domestic

Relative quantitative PCR to assess bacterial community dynamics during biodegradation of diesel and biodiesel fuels under various aeration conditions.

PubMed

Cyplik, Paweł; Schmidt, Marcin; Szulc, Alicja; Marecik, Roman; Lisiecki, Piotr; Heipieper, Hermann J; Owsianiak, Mikołaj; Vainshtein, Mikhail; Chrzanowski, Łukasz

2011-03-01

The degradation of diesel fuel, B20 blend and biodiesel in liquid cultures by a seven-member bacterial consortium was compared under conditions with full aeration or with limited aeration with nitrate added as main electron acceptor. Community dynamics was assessed employing real-time PCR and the ddCt method for relative quantification. Biodegradation rates increased with increasing biodiesel content, but were significantly reduced under conditions with nitrate. Despite large variations in biodegradation rates, magnitude changes in population numbers were typically observed only from zero to one order, regardless the type of fuel and electron acceptor. Only Comamonadaceae and Variovorax sp. distinctly preferred aerobic conditions, and during aerobic growth showed suppression as fuel contained more biodiesel. Thus, the consortium is relatively stable and most of the degraders can shift their metabolism from hydrocarbons to biodiesel. The stability of the consortium is of interest in the context of biodiesel-mediated biodegradation of petroleum hydrocarbons. Copyright © 2010 Elsevier Ltd. All rights reserved.

Biological aerated filter treated textile washing wastewater for reuse after ozonation pre-treatment.

PubMed

Wang, X J; Chen, S L; Gu, X Y; Wang, K Y; Qian, Y Z

2008-01-01

The combination of chemical and biological treatment processes is a promising technique to reduce refractory organics from wastewater. Ozonation can achieve high color removal, enhance biodegradability, and reduce the chemical oxygen demand (COD). The biological technique can further decrease COD of wastewater after ozonation as a pre-treatment. In this study the ozonizing-biological aerated filter processes were used to treat textile washing wastewater for reuse after conventional treatment. The result showed that when the influent qualities were COD about 80 mg/L, color 16 degree and turbidity about 8 NTU, using the combination processes with the dosages of ozone at 30-45 mg/L with the hydraulic retention time (HRT) of biological aerated filter (BAF) at 3-4 hours respectively, gave effluent qualities of COD less than 30 mg/L, color 2 degree and turbidity less than 1NTU. The cost of treatment was less than one yuan/t wastewater, and these processes could enable high quality washing water reuse in textile industry. Copyright IWA Publishing 2008.

Aeration costs in stirred-tank and bubble column bioreactors

DOE PAGES

Humbird, D.; Davis, R.; McMillan, J. D.

2017-08-10

To overcome knowledge gaps in the economics of large-scale aeration for production of commodity products, Aspen Plus is used to simulate steady-state oxygen delivery in both stirred-tank and bubble column bioreactors, using published engineering correlations for oxygen mass transfer as a function of aeration rate and power input, coupled with new equipment cost estimates developed in Aspen Capital Cost Estimator and validated against vendor quotations. Here, these simulations describe the cost efficiency of oxygen delivery as a function of oxygen uptake rate and vessel size, and show that capital and operating costs for oxygen delivery drop considerably moving from standard-sizemore » (200 m 3) to world-class size (500 m 3) reactors, but only marginally in further scaling up to hypothetically large (1000 m 3) reactors. Finally, this analysis suggests bubble-column reactor systems can reduce overall costs for oxygen delivery by 10-20% relative to stirred tanks at low to moderate oxygen transfer rates up to 150 mmol/L-h.« less

Palm oil mill effluent and municipal wastewater co-treatment by zeolite augmented sequencing batch reactors: Turbidity removal

NASA Astrophysics Data System (ADS)

Farraji, Hossein; Zaman, Nastaein Qamaruz; Aziz, Hamidi Abdul; Sa'at, Siti Kamariah Md

2017-10-01

Palm oil mill effluent (POME) is the largest wastewater in Malaysia. Of the 60 million tons of POME produced annually, 2.4-3 million tons are total solids. Turbidity is caused by suspended solids, and 75% of total suspended solids are organic matter. Coagulation and flocculation are popular treatments for turbidity removal. Traditional commercial treatments do not meet discharge standards. This study evaluated natural zeolite and municipal wastewater (MWW)-augmented sequencing batch reactor as a microbiological digestion method for the decontamination of POME in response surface methodology. Aeration, contact time, and MWW/POME ratio were selected as response factors for turbidity removal. Results indicated that turbidity removal varied from 96.7% (MWW/POME ratio=50 %, aeration flow=0.5 L/min, and contact time=12) to 99.31% (MWW/POME ratio=80%, aeration flow 4L/min, and contact time 12 h). This study is the first to present MWW augmentation as a suitable microorganism supplier for turbidity biodegradation in high-strength agroindustrial wastewater.

Influence of addition of calcium sulfate dihydrate on drying of autoclaved aerated concrete

NASA Astrophysics Data System (ADS)

Małaszkiewicz, Dorota; Chojnowski, Jacek

2017-11-01

The quality of the autoclaved aerated concrete (AAC) strongly depends on the chemical composition of the raw materials, as well as on the process of the hydrothermal reaction during autoclaving. Performance parameters depend on material structure: fine micron-scale matrix porosity generated by the packing of thin tobermorite plates and coarse aeration pores arising from the foaming of wet mix. In this study the binder varied in calcium sulfate dihydrate (CaSO4ṡ2H2O) content. Five series of AAC specimens were produced, with gypsum content 0; 0.55; 1.15; 2.3 and 3.5% of dry mass respectively. AAC units were produced in UNIPOL technology. The study presents experimental results of AAC moisture stabilization. The initial moisture content was determined directly after autoclaving. Slower drying process was observed for samples containing over 2% of gypsum. Whereas other performance parameters, compressive and tensile strength, as well as water absorption and capillary rise, were significantly better comparing to the reference AAC samples.

Synergism of Pseudomonas aeruginosa and Fe0 for treatment of heavy metal contaminated effluents using small scale laboratory reactor.

PubMed

Singh, Rajesh; Bishnoi, Narsi R; Kirrolia, Anita; Kumar, Rajender

2013-01-01

In this study Pseudomonas aeruginosa a metal tolerant strain was not only applied for heavy metal removal but also to the solublization performance of the precipitated metal ions during effluent treatment. The synergistic effect of the isolate and Fe(0) enhanced the metal removal potential to 72.97% and 87.63% for Cr(VI) and cadmium, respectively. The decrease in cadmium ion removal to 43.65% (aeration+stirring reactors), 21.33% (aerated reactors), and 18.95% (without aerated+without stirring) with an increase in incubation period not only indicate the presence of soluble less toxic complexes, but also help in exploration of the balancing potential for valuable metal recovery. A relatively best fit and significant values of the correlation coefficient 0.912, 0.959, and 0.9314 for mixed effluent (Paint Industry effluent+CETP Wazirpur, effluent), CETP, Wazirpur, and control effluents, respectively, indicating first-order formulation and provide a reasonable description of COD kinetic data. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effect of Autoclaved Aerated Concrete Modification with High-Impact Polystyrene on Sound Insulation

NASA Astrophysics Data System (ADS)

Brelak, Sylwia; Dachowski, Ryszard

2017-10-01

Autoclaved aerated concrete is one of the most commonly used building materials. Its advantages include low density, high thermal insulation capacity and high fire resistance. It has a relatively high compressive strength, though not high enough to be able to compete with other building materials in this respect. One of the directions leading to the improvement of physical and mechanical properties of autoclaved aerated concrete is the modification of its composition. A noticeable effect of pulverized high-impact polystyrene (improved compressive strength and water absorption) was relevant for the decision to continue the study of its effects. This paper discusses the effect of high-impact polystyrene on sound insulation in AAC products. The tests demonstrated a positive influence of the modifier on AAC sound insulation enhancement. Results from the tests performed on HIPS-modified AAC products were showed and compared with the properties of conventional products. The effect of the polymer on the microstructure of the products obtained was described briefly.

The effects of temperature and aeration on the corrosion of A508III low alloy steel in boric acid solutions at 25-95 °C

NASA Astrophysics Data System (ADS)

Xiao, Qian; Lu, Zhanpeng; Chen, Junjie; Yao, Meiyi; Chen, Zhen; Ejaz, Ahsan

2016-11-01

The effects of temperature, solution composition and dissolved oxygen on the corrosion rate and electrochemical behavior of an A508III low alloy steel in boric acid solution with lithium hydroxide at 25-95 °C are investigated. In aerated solutions, increasing the boric acid concentration increases the corrosion rate and the anodic current density. The corrosion rate in deaerated solutions increases with increasing temperature. A corrosion rate peak value is found at approximately 75 °C in aerated solutions. Increasing temperature increases the oxygen diffusion coefficient, decreases the dissolved oxygen concentration, accelerates the hydrogen evolution reaction, and accelerates both the active dissolution and the film forming reactions. Increasing dissolved oxygen concentration does not significantly affect the corrosion rate at 50 and 60 °C, increases the corrosion rate at 70 and 80 °C, and decreases the corrosion rate at 87.5 and 95 °C in a high concentration boric acid solution with lithium hydroxide.

The seasonal variation of emission of greenhouse gases from a full-scale sewage treatment plant.

PubMed

Masuda, Shuhei; Suzuki, Shunsuke; Sano, Itsumi; Li, Yu-You; Nishimura, Osamu

2015-12-01

The seasonal variety of greenhouse gas (GHGs) emissions and the main emission source in a sewage treatment plant were investigated. The emission coefficient to treated wastewater was 291gCO2m(-3). The main source of GHGs was CO2 from the consumption of electricity, nitrous oxide from the sludge incineration process, and methane from the water treatment process. They accounted for 43.4%, 41.7% and 8.3% of the total amount of GHGs emissions, respectively. The amount of methane was plotted as a function of water temperature ranging between 13.3 and 27.3°C. An aeration tank was the main source of methane emission from all the units. Almost all the methane was emitted from the aeration tank, which accounted for 86.4% of the total gaseous methane emission. However, 18.4% of the methane was produced in sewage lines, 15.4% in the primary sedimentation tank, and 60.0% in the aeration tank. Copyright © 2014 Elsevier Ltd. All rights reserved.

Radon removal using point-of-entry water-treatment techniques. Final report, October 1988-June 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinner, N.E.; Malley, J.P.; Clement, J.A.

1990-10-01

The purpose of the EPA Cooperative Agreement was to evaluate the performance of POE granular activated carbon (GAC), and diffused bubble and bubble place aeration systems treating a ground water supply containing radon (35,620 + or - 6,717 pCi/L). The pattern of loading to the units was designed to simulate daily demand in a household. Each of the systems was evaluated with respect to three primary factors: radon removal efficiency, potential problems, and economics. The radon removal efficiencies of the POE GAC units gradually deteriorated over time from 99.7% to 79% for the GAC without pretreatment and 99.7% to 85%more » for the units preceded by ion exchange. The bubble plate and diffused bubble POE units were very efficient (99%) at removing radon from the water. The resilience is primarly due to the high air to water ratios supplied by the aeration blowers. One major problem associated with the aeration techniques is iron oxidation/precipitation.« less

Treatment of variable and intermittently flowing wastewaters.

PubMed

Kocasoy, Günay

1993-11-01

The biological treatment of wastewaters originating from hotels and residential areas of seasonal use, flowing intermittently, is difficult due to the fact that bacteria cannot survive during periods of no-flow. An investigation has been conducted in order to develop a system which will be able to overcome the difficulties encountered. After a long investigation the following system has given satisfactory results. The wastewater was taken initially into an aeration tank operating as a sequential batch reactor. Waste was taken after the sedimentation phase of the reactor into a coagulation-flocculation tank where it was treated by chemical means, and then settled in order to separate the floes. When the population of bacteria in the aeration tank reached the required level, the physico-chemical treatment was terminated and the tank used for chemical treatment has been started to be used as an equalization tank while the aeration and sedimentation tanks have been used as an activated sludge unit. This system has been proved to be a satisfactory method for the above mentioned wastes.

Aeration costs in stirred-tank and bubble column bioreactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humbird, D.; Davis, R.; McMillan, J. D.

To overcome knowledge gaps in the economics of large-scale aeration for production of commodity products, Aspen Plus is used to simulate steady-state oxygen delivery in both stirred-tank and bubble column bioreactors, using published engineering correlations for oxygen mass transfer as a function of aeration rate and power input, coupled with new equipment cost estimates developed in Aspen Capital Cost Estimator and validated against vendor quotations. Here, these simulations describe the cost efficiency of oxygen delivery as a function of oxygen uptake rate and vessel size, and show that capital and operating costs for oxygen delivery drop considerably moving from standard-sizemore » (200 m 3) to world-class size (500 m 3) reactors, but only marginally in further scaling up to hypothetically large (1000 m 3) reactors. Finally, this analysis suggests bubble-column reactor systems can reduce overall costs for oxygen delivery by 10-20% relative to stirred tanks at low to moderate oxygen transfer rates up to 150 mmol/L-h.« less

Treatment of synthetic kraft evaporator condensate using thermophilic and mesophilic membrane aerated biofilm reactors.

PubMed

Liao, B Q; Zheng, M R; Ratana-Rueangsri, L

2010-01-01

A comparative study on the treatment of synthetic kraft evaporator condensate was conducted using thermophilic (55 degrees C) and mesophilic (30 degrees C) membrane aerated biofilm reactors (MABRs) and sequencing batch reactors (SBRs) for 8 months. Under tested conditions, a chemical oxygen demand (COD) removal efficiency of 80-95% was achieved with both thermophilic and mesophilic MABRs and SBRs. The COD removal efficiency of thermophilic MABR (80-90%) was slightly lower than that of the mesophilic MABR (85-95%) and the thermophilic SBR (90-95%). A significant amount (13-37%) of COD was stripped by conventional aeration in the SBRs, while stripping in MABRs was negligible. Simultaneous COD removal and denitrification were observed in the mesophilic MABR, while the thermophilic MABR contributed mainly for COD removal. Nitrification was not significant in both the thermophilic and mesophilic MABRs. The results suggest that treatment of kraft evaporator condensate is feasible with the use of both thermophilic and mesophilic MABRs in terms of COD removal with the advantages of negligible stripping.

Biogas production enhancement using semi-aerobic pre-aeration in a hybrid bioreactor landfill.

PubMed

Cossu, Raffaello; Morello, Luca; Raga, Roberto; Cerminara, Giulia

2016-09-01

Landfilling continues to be one of the main methods used in managing Municipal Solid Waste (MSW) worldwide, particularly in developing countries. Although in many countries national legislation aims to reduce this practice as much as possible, landfill is a necessary and unavoidable step in closing the material cycle. The need for innovative waste management techniques to improve landfill management and minimize the adverse environmental impact produced has resulted in an increasing interest in innovative systems capable of accelerating waste stabilization. Landfill bioreactors allow decomposition kinetics to be increased and post-operational phase to be shortened; in particular, hybrid bioreactors combine the benefits afforded by both aerobic and anaerobic processes. Six bioreactor simulators were used in the present study: four managed as hybrid, with an initial semi-aerobic phase and a second anaerobic phase, and two as anaerobic control bioreactors. The main goal of the first aerated phase is to reduce Volatile Fatty Acids (VFA) in order to increase pH and enhance methane production during the anaerobic phase; for this reason, air injection was stopped only when these parameters reached the optimum range for methanogenic bacteria. Biogas and leachate were constantly monitored throughout the entire methanogenic phase with the aim of calibrating a Gompertz Model and evaluating the effects of pre-aeration on subsequent methane production. The results showed that moderate and intermittent pre-aeration produces a positive effect both on methane potential and in the kinetics of reaction. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quicklime-induced changes of soil properties: Implications for enhanced remediation of volatile chlorinated hydrocarbon contaminated soils via mechanical soil aeration.

PubMed

Ma, Yan; Dong, Binbin; He, Xiaosong; Shi, Yi; Xu, Mingyue; He, Xuwen; Du, Xiaoming; Li, Fasheng

2017-04-01

Mechanical soil aeration is used for soil remediation at sites contaminated by volatile organic compounds. However, the effectiveness of the method is limited by low soil temperature, high soil moisture, and high soil viscosity. Combined with mechanical soil aeration, quicklime has a practical application value related to reinforcement remediation and to its action in the remediation of soil contaminated with volatile organic compounds. In this study, the target pollutant was trichloroethylene, which is a volatile chlorinated hydrocarbon pollutant commonly found in contaminated soils. A restoration experiment was carried out, using a set of mechanical soil-aeration simulation tests, by adding quicklime (mass ratios of 3, 10, and 20%) to the contaminated soil. The results clearly indicate that quicklime changed the physical properties of the soil, which affected the environmental behaviour of trichloroethylene in the soil. The addition of CaO increased soil temperature and reduced soil moisture to improve the mass transfer of trichloroethylene. In addition, it improved the macroporous cumulative pore volume and average pore size, which increased soil permeability. As soil pH increased, the clay mineral content in the soils decreased, the cation exchange capacity and the redox potential decreased, and the removal of trichloroethylene from the soil was enhanced to a certain extent. After the addition of quicklime, the functional group COO of soil organic matter could interact with calcium ions, which increased soil polarity and promoted the removal of trichloroethylene. Copyright © 2017 Elsevier Ltd. All rights reserved.

Treatment of highly polluted groundwater by novel iron removal process.

PubMed

Sim, S J; Kang, C D; Lee, J W; Kim, W S

2001-01-01

The removal of ferrous iron (Fe(II)) in groundwater has been generally achieved by simple aeration, or the addition of an oxidizing agent. Aeration has been shown to be very efficient in insolubilization ferrous iron at a pH level greater than 6.5. In this study, pH was maintained over 6.5 using limestone granules under constant aeration to oxidize ferrous iron in groundwater in a limestone packed column. A sedimentation unit coupled with a membrane filtration was also developed to precipitate and filtrate the oxidized ferric compound simultaneously. Several bench-scale studies, including the effects of the limestone granule sizes, amounts and hydraulic retention time on iron removal in the limestone packed column were investigated. It was found that 550 g/L of the 7-8 mesh size limestone granules, and 20 min of hydraulic retention time in the limestone packed column, were necessary for the sufficient oxidation of 40 mg/L of iron(II) in groundwater. Long-term operation was successfully achieved in contaminated waters by removing the iron deposits on the surface of the limestone granule by continuous aeration from the bottom of the column. Periodic reverse flow helped to remove caking and fouling of membrane surface caused by the continuous filtration. Recycling of the treated water from the membrane right after reverse flow operation made possible an admissible limit of iron concentration of the treated water for drinking. The pilot-scale process was constructed and has been tested in the rural area of Korea.

Effect of operation parameters on the flux stabilization of gravity-driven membrane (GDM) filtration system for decentralized water supply.

PubMed

Tang, Xiaobin; Ding, An; Qu, Fangshu; Jia, Ruibao; Chang, Haiqing; Cheng, Xiaoxiang; Liu, Bin; Li, Guibai; Liang, Heng

2016-08-01

A pilot-scale gravity-driven membrane (GDM) filtration system under low gravitational pressure without any pre-treatment, backwash, flushing, or chemical cleaning was carried out to investigate the effect of operation parameters (including operation pressure, aeration mode, and intermittent filtration) on the effluent quality and permeability development. The results revealed that GDM system exhibited an efficient performance for the removal of suspended substances and organic compounds. The stabilization of flux occurred and the average values of stable flux were 6.6, 8.1, and 8.6 Lm(-2) h(-1) for pressures of 65, 120, and 200 mbar, respectively. In contrast, flux stabilization was not observed under continuous and intermittent aeration conditions. However, aeration (especially continuous aeration) was effective to improve flux and alleviate membrane fouling during 1-month operation. Moreover, intermittent filtration would influence the stabilization of permeate flux, resulting in a higher stable flux (ranging from 6 to 13 Lm(-2) h(-1)). The stable flux significantly improved with the increase of intermittent period. Additionally, GDM systems exhibited an efficient recovery of flux after simple physical cleaning and the analyses of resistance reversibility demonstrated that most of the total resistance was hydraulic reversible resistance (50-75 %). Therefore, it is expected that the results of this study can develop strategies to increase membrane permeability and reduce energy consumption in GDM systems for decentralized water supply.

Recovery of Stored Aerobic Granular Sludge and Its Contaminants Removal Efficiency under Different Operation Conditions

PubMed Central

Zhao, Zhiwei; Shi, Wenxin; Li, Ji

2013-01-01

The quick recovery process of contaminants removal of aerobic granular sludge (AGS) is complex, and the influencing factors are still not clear. The effects of dissolved oxygen (DO, air intensive aeration rate), organic loading rate (OLR), and C/N on contaminants removal characteristics of AGS and subsequently long-term operation of AGS bioreactor were investigated in this study. DO had a major impact on the recovery of AGS. The granules reactivated at air intensive aeration rate of 100 L/h achieved better settling property and contaminants removal efficiency. Moreover, protein content in extracellular polymeric substance (EPS) was almost unchanged, which demonstrated that an aeration rate of 100 L/h was more suitable for maintaining the biomass and the structure of AGS. Higher OLR caused polysaccharides content increase in EPS, and unstable C/N resulted in the overgrowth of filamentous bacteria, which presented worse NH4 +-N and PO4 3−-P removal. Correspondingly, quick recovery of contaminants removal was accomplished in 12 days at the optimized operation conditions of aeration rate 100 L/h, OLR 4 g/L·d, and C/N 100 : 10, with COD, NH4 +-N, and PO4 3−-P removal efficiencies of 87.2%, 86.9%, and 86.5%, respectively. The renovation of AGS could be successfully utilized as the seed sludge for the rapid start-up of AGS bioreactor. PMID:24106695

The improvement of thermal characteristics of autoclave aerated concrete for energy efficient high-rise buildings application

NASA Astrophysics Data System (ADS)

Khavanov, Pavel; Fomina, Ekaterina; Kozhukhova, Natalia

2018-03-01

Nowadays, the problem of energy saving is very relevant. One of the ways to reduction energy consumption in construction materials production and construction of civil and industrial high-rise buildings is the application of claddings with heat-insulating performance. The concept of energy efficiency of high-rise buildings is closely related to environmental aspect and sustainability of applied construction materials; reducing service costs; energy saving and microclimate comfortability. A complexity of architectural and structural design as well as aesthetic characteristics of construction materials are also should be considered. The high interest focused on materials with combined properties. This work is oriented on the study of energy efficiency of buildings by improving heat-insulation and strength performance of autoclave aerated concrete. The applied method of sulfate activation of lime allows monitoring phase and structure formation in aerated concrete. The optimal mix design of aerated concrete with the compressive strength up to 8.5 MPa and decreased density up to 760 kg/m3 was proposed. Analysis of structure at macro-and microscale was performed as well as the criteria of an optimal porosity formation was considered a number, size, shape of pore and density of interior partition. SEM analysis and BET method were performed in this research work. The research results demonstrated the correlation between structure and vapor permeability resistance, also it was found that the increase of strength can lead to reduction of thermal conductivity.

In situ disinfection of sewage contaminated shallow groundwater: a feasibility study.

PubMed

Bailey, Morgan M; Cooper, William J; Grant, Stanley B

2011-11-01

Sewage-contaminated shallow groundwater is a potential cause of beach closures and water quality impairment in marine coastal communities. In this study we set out to evaluate the feasibility of several strategies for disinfecting sewage-contaminated shallow groundwater before it reaches the coastline. The disinfection rates of Escherichia coli (EC) and enterococci bacteria (ENT) were measured in mixtures of raw sewage and brackish shallow groundwater collected from a coastal community in southern California. Different disinfection strategies were explored, ranging from benign (aeration alone, and aeration with addition of brine) to aggressive (chemical disinfectants peracetic acid (PAA) or peroxymonosulfate (Oxone)). Aeration alone and aeration with brine did not significantly reduce the concentration of EC and ENT after 6 h of exposure, while 4-5 mg L(-1) of PAA or Oxone achieved >3 log reduction after 15 min of exposure. Oxone disinfection was more rapid at higher salinities, most likely due to the formation of secondary oxidants (e.g., bromine and chlorine) that make this disinfectant inappropriate for marine applications. Using a Lagrangian modeling framework, we identify several factors that could influence the performance of in-situ disinfection with PAA, including the potential for bacterial regrowth, and the non-linear dependence of disinfection rate upon the residence time of water in the shallow groundwater. The data and analysis presented in this paper provide a framework for evaluating the feasibility of in-situ disinfection of shallow groundwater, and elucidate several topics that warrant further investigation. Copyright © 2011 Elsevier Ltd. All rights reserved.

Real-Time Ultrafine Aerosol Measurements from Wastewater Treatment Facilities.

PubMed

Piqueras, P; Li, F; Castelluccio, V; Matsumoto, M; Asa-Awuku, A

2016-10-18

Airborne particle emissions from wastewater treatment plants (WWTP) have been associated with health repercussions but particulate quantification studies are scarce. In this study, particulate matter (PM) number concentrations and size distributions in the ultrafine range (7-300 nm) were measured from two different sources: a laboratory-scale aerobic bioreactor and the activated sludge aeration basins at Orange County Sanitation District (OCSD). The relationships between wastewater parameters (total organic carbon (TOC), chemical oxygen demand (COD), and total suspended solids (TSS)), aeration flow rate and particle concentrations were also explored. A significant positive relationship was found between particle concentration and WWTP variables (COD: r(10) = 0.876, p <.001, TOC: r(10) = 0.664, p <.05, TSS: r(10) = 0.707, p <.05, aeration flow rate: r(8) = 0.988, p <.0001). A theoretical model was also developed from empirical data to compare real world WWTP aerosol number emission fluxes with laboratory data. Aerosol number fluxes at OCSD aerated basins (9.8 × 10 4 lbs/min·cm 2 ) and the bioreactor (7.95 × 10 4 lbs/min·cm 2 ) were calculated and showed a relatively small difference (19%). The ultrafine size distributions from both systems were consistent, with a mode of ∼48 nm. The average mass concentration (7.03 μg/cm 3 ) from OCSD was relatively small compared to other urban sources. However, the in-tank average number concentration of airborne particles (14 480 lbs/cm 3 ) was higher than background ambient concentrations.

Combined discrete particle and continuum model predicting solid-state fermentation in a drum fermentor.

PubMed

Schutyser, M A I; Briels, W J; Boom, R M; Rinzema, A

2004-05-20

The development of mathematical models facilitates industrial (large-scale) application of solid-state fermentation (SSF). In this study, a two-phase model of a drum fermentor is developed that consists of a discrete particle model (solid phase) and a continuum model (gas phase). The continuum model describes the distribution of air in the bed injected via an aeration pipe. The discrete particle model describes the solid phase. In previous work, mixing during SSF was predicted with the discrete particle model, although mixing simulations were not carried out in the current work. Heat and mass transfer between the two phases and biomass growth were implemented in the two-phase model. Validation experiments were conducted in a 28-dm3 drum fermentor. In this fermentor, sufficient aeration was provided to control the temperatures near the optimum value for growth during the first 45-50 hours. Several simulations were also conducted for different fermentor scales. Forced aeration via a single pipe in the drum fermentors did not provide homogeneous cooling in the substrate bed. Due to large temperature gradients, biomass yield decreased severely with increasing size of the fermentor. Improvement of air distribution would be required to avoid the need for frequent mixing events, during which growth is hampered. From these results, it was concluded that the two-phase model developed is a powerful tool to investigate design and scale-up of aerated (mixed) SSF fermentors. Copyright 2004 Wiley Periodicals, Inc.

Method of aeration disinfecting and drying grain in bulk and pretreating seeds and a transverse blow silo grain dryer therefor

DOEpatents

Danchenko, Vitaliy G [Dnipropetrovsk, UA; Noyes, Ronald T [Stillwater, OK; Potapovych, Larysa P [Dnipropetrovsk, UA

2012-02-28

Aeration drying and disinfecting grain crops in bulk and pretreating seeds includes passing through a bulk of grain crops and seeds disinfecting and drying agents including an ozone and air mixture and surrounding air, subdividing the disinfecting and drying agents into a plurality of streams spaced from one another in a vertical direction, and passing the streams at different heights through levels located at corresponding heights of the bulk of grain crops and seeds transversely in a substantially horizontal direction.

Fiber Attachment Module Experiment (FAME): Using a Multiplexed Miniature Hollow Fiber Membrane Bioreactor Solution for Rapid Process Testing

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.; Lunn, Griffin M.; Koss, Lawrence L.; Hummerick, Mary E.; Spencer, Lachelle E.; Johnsey, Marissa N.; Richards, Jeffrey T.; Ellis, Ronald; Birmele, Michele N.; Wheeler, Raymond M.

2014-01-01

Bioreactor research is mostly limited to continuous stirred-tank reactors (CSTRs) which are not an option for microgravity (g) applications due to the lack of a gravity gradient to drive aeration as described by the Archimedes principle. Bioreactors and filtration systems for treating wastewater in g could avoid the need for harsh pretreatment chemicals and improve overall water recovery. Solution: Membrane Aerated Bioreactors (MABRs) for g applications, including possible use for wastewater treatment systems for the International Space Station (ISS).

Economic Evaluation of Two Biological Processes for Treatment of Ball Powder Production Wastewater

DTIC Science & Technology

1989-02-01

Collection and Equalization 2-1 2.2 System 200 - pH and Nutrient Control 2-1 2.3 System 300 - Extended Aeration and Aerobic Digestion 2-4 2.4 System...400 - Sequencing Batch Reactor and Aerobic Digestion 2-4 2.5 System 500 - Sludge Dewatering and Control Building 2-7 1 3.0 COST ESTIMATION AND...Extended Aeration and Aerobic Digestion 2-5 2.4 400 - Sequencing Batch Reactors and Aerobic Digestion 2-6 2.5 500 - Sludge Dewatering 2-8 Artur D Little

Determination of iron: In the presence of chromium and titanium with the jones reductor

USGS Publications Warehouse

Grimaldi, F.S.; Stevens, R.E.; Carron, M.K.

1943-01-01

Sulfuric acid solutions of titanous and chromous sulfates, obtained by passage through the Jones reductor, are oxidized by aeration for from 5 to 10 minutes in the presence of a trace of copper sulfate as a catalyst. Ferrous sulfate is essentially unoxidized and is titrated with permanganate after aeration. Best results are obtained by using 0.0003 millimole of copper sulfate in about 300 ml. of solution. Larger quantities of copper sulfate lead to slightly low results when both chromium and titanium are present.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandstätter, Christian, E-mail: bran.chri@gmail.com; Laner, David, E-mail: david.laner@tuwien.ac.at; Fellner, Johann, E-mail: johann.fellner@tuwien.ac.at

Graphical abstract: Display Omitted - Highlights: • 40 year old waste from an old MSW landfill was incubated in LSR experiments. • Carbon balances for anaerobic and aerobic waste degradation were established. • The transformation of carbon pools during waste degradation was investigated. • Waste aeration resulted in the formation of a new, stable organic carbon pool. • Water addition did not have a significant effect on aerobic waste degradation. - Abstract: Landfill aeration has been proven to accelerate the degradation of organic matter in landfills in comparison to anaerobic decomposition. The present study aims to evaluate pools of organicmore » matter decomposing under aerobic and anaerobic conditions using landfill simulation reactors (LSR) filled with 40 year old waste from a former MSW landfill. The LSR were operated for 27 months, whereby the waste in one pair was kept under anaerobic conditions and the four other LSRs were aerated. Two of the aerated LSR were run with leachate recirculation and water addition and two without. The organic carbon in the solid waste was characterized at the beginning and at the end of the experiments and major carbon flows (e.g. TOC in leachate, gaseous CO{sub 2} and CH{sub 4}) were monitored during operation. After the termination of the experiments, the waste from the anaerobic LSRs exhibited a long-term gas production potential of more than 20 NL kg{sup −1} dry waste, which corresponded to the mineralization of around 12% of the initial TOC (67 g kg{sup −1} dry waste). Compared to that, aeration led to threefold decrease in TOC (32–36% of the initial TOC were mineralized), without apparent differences in carbon discharge between the aerobic set ups with and without water addition. Based on the investigation of the carbon pools it could be demonstrated that a bit more than 10% of the initially present organic carbon was transformed into more recalcitrant forms, presumably due to the formation of humic substances. The source of anaerobic degradation could be identified mainly as cellulose which played a minor role during aerobic degradation in the experiment.« less

Odorous gaseous emissions as influence by process condition for the forced aeration composting of pig slaughterhouse sludge.

PubMed

Blazy, V; de Guardia, A; Benoist, J C; Daumoin, M; Lemasle, M; Wolbert, D; Barrington, S

2014-07-01

Compost sustainability requires a better control of its gaseous emissions responsible for several impacts including odours. Indeed, composting odours have stopped the operation of many platforms and prevented the installation of others. Accordingly, present technologies collecting and treating gases emitted from composting are not satisfactory and alternative solutions must be found. Thus, the aim of this paper was to study the influence of composting process conditions on gaseous emissions. Pig slaughterhouse sludge mixed with wood chips was composted under forced aerationin 300 L laboratory reactors. The process conditions studied were: aeration rate of 1.68, 4.03, 6.22, 9.80 and 13.44 L/h/kg of wet sludge; incorporation ratio of 0.55, 0.83 and 1.1 (kg of wet wood chips/kg of wet sludge), and; bulking agent particles size of <10, 10<20 and 20<30 mm. Out-going gases were sampled every 2 days and their composition was analysed using gas chromatography coupled with mass spectrometry (GC-MS). Fifty-nine compounds were identified and quantified. Dividing the cumulated mass production over 30 days of composting, by odour threshold, 9 compounds were identified as main potential odour contributors: hydrogen sulphide, trimethylamine, ammonia, 2-pentanone, 1-propanol-2-methyl, dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide and acetophenone. Five gaseous compounds were correlated with both aeration rate and bulking agent to waste ratio: hydrogen sulphide, trimethylamine, ammonia, 2-pentanone and 1-propanol-2-methyl. However, dropping the aeration rate and increasing the bulking agent to waste ratio reduced gaseous odour emissions by a factor of 5-10, when the required threshold dilution factor ranged from 10(5) to 10(6), to avoid nuisance at peak emission rates. Process influence on emissions of dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide were poorly correlated with both aeration rate and bulking agent to waste ratio as a reaction with hydrogen sulphide was suspected. Acetophenone emissions originated from the wood chips. Olfactory measurements need to be correlated to gaseous emissions for a more accurate odour emission evaluation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cyber-physical system for a water reclamation plant: Balancing aeration, energy, and water quality to maintain process resilience

NASA Astrophysics Data System (ADS)

Zhu, Junjie

Aeration accounts for a large fraction of energy consumption in conventional water reclamation plants (WRPs). Although process operations at older WRPs can satisfy effluent permit requirements, they typically operate with excess aeration. More effective process controls at older WRPs can be challenging as operators work to balance higher energy costs and more stringent effluent limitations while managing fluctuating loads. Therefore, understandings of process resilience or ability to quickly return to original operation conditions at a WRP are important. A state-of-art WRP should maintain process resilience to deal with different kinds of perturbations even after optimization of energy demands. This work was to evaluate the applicability and feasibility of cyber-physical system (CPS) for improving operation at Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) Calumet WRP. In this work, a process model was developed and used to better understand the conditions of current Calumet WRP, with additional valuable information from two dissolved oxygen field measurements. Meanwhile, a classification system was developed to reveal the pattern of historical influent scenario based on cluster analysis and cross-tabulation analysis. Based on the results from the classification, typical process control options were investigated. To ensure the feasibility of information acquisition, the reliability and flexibility of soft sensors were assessed to typical influent conditions. Finally, the process resilience was investigated to better balance influent perturbations, energy demands, and effluent quality for long-term operations. These investigations and evaluations show that although the energy demands change as the influent conditions and process controls. In general, aeration savings could be up to 50% from the level of current consumption; with a more complex process controls, the saving could be up to 70% in relatively steady-state conditions and at least 40% in relatively challenging transient conditions. The soft sensors can provide reliable and flexible performance on target predictions. The plant can still maintain at a similar level of process resilience after 50% aeration saving, even during long-term perturbations. Overall, this work shows that it is well feasible to provide more cost-effective operations at the Calumet WRP, and meanwhile influent perturbations, effluent quality, and process resilience are well in balance.

Liquid and atmospheric ammonia concentrations from a dairy lagoon during an aeration experiment

NASA Astrophysics Data System (ADS)

Rumburg, Brian; Neger, Manjit; Mount, George H.; Yonge, David; Filipy, Jenny; Swain, John; Kincaid, Ron; Johnson, Kristen

Ammonia emissions from agriculture are an environmental and human health concern, and there is increasing pressure to reduce emissions. Animal agriculture is the largest global source of ammonia emissions and on a per cow basis dairy operations are the largest emitters. The storage and disposal of the dairy waste is one area where emissions can be reduced, aerobic biological treatment of wastewater being a common and effective way of reducing ammonia emissions. An aeration experiment in a dairy lagoon with two commercial aerators was performed for 1 month. Liquid concentrations of ammonia, total nitrogen, nitrite and nitrate were monitored before, during and after the experiment and atmospheric ammonia was measured downwind of the lagoon using a short-path differential optical absorption spectroscopy (DOAS) instrument with 1 ppbv sensitivity. No changes in either liquid or atmospheric ammonia concentrations were detected throughout the experiment, and neither dissolved oxygen, nitrite nor nitrate could be detected in the lagoon at any time. The average ammonia concentration at 10 sampling sites in the lagoon at a depth of 0.15 m was 650 mg l -1 and at 0.90 m it was 700 mg l -1 NH 3-N. The average atmospheric ammonia concentration 50 m downwind was about 300 ppbv. The 0.90 m depth total nitrogen concentrations and total and volatile solids concentrations decreased during the experiment due to some mixing of the lagoon but the 0.15 m depth concentrations did not decrease indicating that the aerators were not strong enough to mix the sludge off the bottom into the whole water column.

Model extension, calibration and validation of partial nitritation-anammox process in moving bed biofilm reactor (MBBR) for reject and mainstream wastewater.

PubMed

Trojanowicz, K; Plaza, E; Trela, J

2017-11-09

In the paper, the extension of mathematical model of partial nitritation-anammox process in a moving bed biofilm reactor (MBBR) is presented. The model was calibrated with a set of kinetic, stoichiometric and biofilm parameters, whose values were taken from the literature and batch tests. The model was validated with data obtained from: laboratory batch experiments, pilot-scale MBBR for a reject water deammonification operated at Himmerfjärden wastewater treatment and pilot-scale MBBR for mainstream wastewater deammonification at Hammarby Sjöstadsverk research facility, Sweden. Simulations were conducted in AQUASIM software. The proposed, extended model proved to be useful for simulating of partial nitritation/anammox process in biofilm reactor both for reject water and mainstream wastewater at variable substrate concentrations (influent total ammonium-nitrogen concentration of 530 ± 68; 45 ± 2.6 and 38 ± 3 gN/m 3 - for reject water - and two cases of mainstream wastewater treatment, respectively), temperature (24 ± 2.8; 15 ± 1.1 and 18 ± 0.5°C), pH (7.8 ± 0.2; 7.3 ± 0.1 and 7.4 ± 0.1) and aeration patterns (continuous aeration and intermittent aeration with variable dissolved oxygen concentrations and length of aerated and anoxic phases). The model can be utilized for optimizing and testing different operational strategies of deammonification process in biofilm systems.

Efficient nitrogen removal via simultaneous nitrification and denitrification in a penicillin wastewater biological treatment plant.

PubMed

Luo, Weiwei; Jin, Xibiao; Yu, Yonglian; Zhou, Sichen; Lu, Shuguang

2014-01-01

Nitrogen-removal performance was investigated in a penicillin wastewater biological treatment plant (P-WWTP) reconstructed from a cyclic activated sludge system (CASS) tank designed for simultaneous nitrification and denitrification (SND). Good performance was obtained during a 900-day operation period, as indicated by effluent chemical oxygen demand (COD), total nitrogen (TN) and ammonia nitrogen (NH₃‒N) values of 318 ± 34, 28.7 ± 2.4 and<0.2 mg L⁻¹ when the influent COD, total Kjeldahl nitrogen (TKN) and NH₃‒N were 3089 ± 453, 251.4 ± 26.5 and 124.8 ± 26.8 mg L⁻¹, respectively. Nitrification and denitrification occurred at different spaces, that is, 71.4% of TN removal occurred in the first 40% of the aeration tank, while 68.8% of the TKN removal occurred in 40-100% of the aeration tank. Sufficient easily biodegradable organics (EBO) in wastewater were key to the occurrence of SND. The denitrification rate under aeration conditions was 10.7 mg N g VSS⁻¹ h⁻¹ when EBO were sufficient, but 0.98 mg N g VSS⁻¹ h⁻¹ when EBO were completely degraded. Nitrification primarily occurred in the rear of the aeration tank owing to the competition for oxygen between carbonaceous oxidation and nitrification. The nitrification rate was only 7.13 mg NOD g VSS⁻¹ h⁻¹ at the beginning of the reaction, but 14.7 mg NOD g VSS⁻¹ h⁻¹ when EBO were completely degraded. These results will facilitate the improvement of nitrogen removal by existing WWTPs.

Kinetics and oxidative mechanism for H2O2-enhanced iron-mediated aeration (IMA) treatment of recalcitrant organic compounds in mature landfill leachate.

PubMed

Deng, Yang; Englehardt, James D

2009-09-30

A hydrogen peroxide (H(2)O(2))-enhanced iron (Fe(0))-mediated aeration (IMA) process has been recently demonstrated to effectively remove organic wastes from mature landfill leachate. In this paper, the kinetics and oxidative mechanisms of the enhanced IMA treatment were studied. Bench-scale full factorial tests were conducted in an orbital shaker reactor for treatment of a mature leachate with an initial chemical oxygen demand (COD) of 900-1200 mg/L. At the maximum aeration rate (8.3 mL air/min mL sample), process variables significantly influencing the rates of H(2)O(2) decay and COD removal were pH (3.0-8.0), initial H(2)O(2) doses (0.21-0.84 M), and Fe(0) surface area concentrations (0.06-0.30 m(2)/L). Empirical kinetic models were developed and verified for the degradation of H(2)O(2) and COD. High DO maintained by a high aeration rate slowed the H(2)O(2) self-decomposition, accelerated Fe(0) consumption, and enhanced the COD removal. In hydroxyl radical (OH*) scavenging tests, the rate of removal of glyoxylic acid (target compound) was not inhibited by the addition of para-chlorobenzoic acid (OH* scavenger) at pH 7.0-7.5, ruling out hydroxyl radical as the principal oxidant in neutral-weakly basic solution. These experimental results show that this enhanced IMA technology is a potential alternative for the treatment of high strength recalcitrant organic wastewaters.

Valorization of a pharmaceutical organic sludge through different composting treatments.

PubMed

Cucina, Mirko; Tacconi, Chiara; Sordi, Simone; Pezzolla, Daniela; Gigliotti, Giovanni; Zadra, Claudia

2018-04-01

Nowadays, the agricultural reuse of pharmaceutical sludge is still limited due to environmental and agronomic issues (e.g. low stabilization of the organic matter, phytotoxicity). The aim of the present study was to evaluate the characteristics of a pharmaceutical sludge derived from the daptomycin production and to study the possibility of improving its quality through composting. The pharmaceutical sludge showed high content of macronutrients (e.g. total Kjeldahl N content was 38 g kg -1 ), but it was also characterized by high salinity (7.9 dS m -1 ), phytotoxicity (germination index was 36.7%) and a low organic matter stabilization. Two different mixtures were prepared (mixture A: 70% sludge + 30% wood chips w/w, mixture B: 45% sludge + 45% wood chips + 10% cereal straw w/w) and treated through static composting using two different aeration systems: active and passive aeration. The mixtures resulted in the production of two different compost, and the evolution of process management parameters was different. The low total solids and organic matter content of mixture A led to the failure of the process. The addition of cereal straw in mixture B resulted in increased porosity and C/N ratio and, consequently, in an optimal development of the composting process (e.g. the final organic matter loss was 54.1% and 63.1% for the passively and actively aerated treatment, respectively). Both passively and actively aerated composting of mixture B improved the quality of the pharmaceutical sludge, by increasing its organic matter stabilization and removing phytotoxicity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sediment Resuspension and Deposition on Seagrass Leaves Impedes Internal Plant Aeration and Promotes Phytotoxic H2S Intrusion.

PubMed

Brodersen, Kasper E; Hammer, Kathrine J; Schrameyer, Verena; Floytrup, Anja; Rasheed, Michael A; Ralph, Peter J; Kühl, Michael; Pedersen, Ole

2017-01-01

HIGHLIGHTS: Sedimentation of fine sediment particles onto seagrass leaves severely hampers the plants' performance in both light and darkness, due to inadequate internal plant aeration and intrusion of phytotoxic H 2 S. Anthropogenic activities leading to sediment re-suspension can have adverse effects on adjacent seagrass meadows, owing to reduced light availability and the settling of suspended particles onto seagrass leaves potentially impeding gas exchange with the surrounding water. We used microsensors to determine O 2 fluxes and diffusive boundary layer (DBL) thickness on leaves of the seagrass Zostera muelleri with and without fine sediment particles, and combined these laboratory measurements with in situ microsensor measurements of tissue O 2 and H 2 S concentrations. Net photosynthesis rates in leaves with fine sediment particles were down to ~20% of controls without particles, and the compensation photon irradiance increased from a span of 20-53 to 109-145 μmol photons m -2 s -1 . An ~2.5-fold thicker DBL around leaves with fine sediment particles impeded O 2 influx into the leaves during darkness. In situ leaf meristematic O 2 concentrations of plants exposed to fine sediment particles were lower than in control plants and exhibited long time periods of complete meristematic anoxia during night-time. Insufficient internal aeration resulted in H 2 S intrusion into the leaf meristematic tissues when exposed to sediment resuspension even at relatively high night-time water-column O 2 concentrations. Fine sediment particles that settle on seagrass leaves thus negatively affect internal tissue aeration and thereby the plants' resilience against H 2 S intrusion.

Effects of aeration and natural zeolite on ammonium removal during the treatment of sewage by mesocosm-scale constructed wetlands.

PubMed

Araya, F; Vera, I; Sáez, K; Vidal, G

2016-01-01

The objective was to evaluate the effects of intermittent artificial aeration cycles and natural zeolite as a support medium, in addition to the contribution of plants (Schoenoplectus californicus) on NH4(+)-N removal during sewage treatment by Constructed Wetlands (CW). Two lines of Mesocosm Constructed Wetland (MCW) were installed: (a) gravel line (i.e. G-Line) and (b) zeolite line (i.e. Z-Line). Aeration increased the NH4(+)-N removal efficiency by 20-45% in the G-Line. Natural zeolite increased the NH4(+)-N removal efficiency by up to 60% in the Z-Line. Plants contributed 15-30% of the NH4(+)-N removal efficiency and no difference between the G-Line and the Z-Line. Conversely, the NH4(+)-N removal rate was shown to only increase with the use of natural zeolite. However, the MCW with natural zeolite, the NH4(+)-N removal rate showed a direct relationship only with the NH4(+)-N influent concentration. Additionally, relationship between the oxygen, energy and area regarding the NH4(+)-N removal efficiency was established for 2.5-12.5 gO2/(kWh-m(2)) in the G-Line and 0.1-2.6 gO2/(kWh-m(2)) in the Z-Line. Finally, it was established that a combination of natural zeolite as a support medium and the aeration strategy in a single CW could regenerate the zeolite's adsorption sites and maintain a given NH4(+)-N removal efficiency over time.

Bioaugmentation of overloaded anaerobic digesters restores function and archaeal community.

PubMed

Tale, V P; Maki, J S; Zitomer, D H

2015-03-01

Adding beneficial microorganisms to anaerobic digesters for improved performance (i.e. bioaugmentation) has been shown to decrease recovery time after organic overload or toxicity upset. Compared to strictly anaerobic cultures, adding aerotolerant methanogenic cultures may be more practical since they exhibit higher methanogenic activity and can be easily dried and stored in ambient air for future shipping and use. In this study, anaerobic digesters were bioaugmented with both anaerobic and aerated, methanogenic propionate enrichment cultures after a transient organic overload. Digesters bioaugmented with anaerobic and moderately aerated cultures recovered 25 and 100 days before non-bioaugmented digesters, respectively. Increased methane production due to bioaugmentation continued a long time, with 50-120% increases 6 to 12 SRTs (60-120 days) after overload. In contrast to the anaerobic enrichment, the aerated enrichments were more effective as bioaugmentation cultures, resulting in faster recovery of upset digester methane and COD removal rates. Sixty days after overload, the bioaugmented digester archaeal community was not shifted, but was restored to one similar to the pre-overload community. In contrast, non-bioaugmented digester archaeal communities before and after overload were significantly different. Organisms most similar to Methanospirillum hungatei had higher relative abundance in well-operating, undisturbed and bioaugmented digesters, whereas organisms similar to Methanolinea tarda were more abundant in upset, non-bioaugmented digesters. Bioaugmentation is a beneficial approach to increase digester recovery rate after transient organic overload events. Moderately aerated, methanogenic propionate enrichment cultures were more beneficial augments than a strictly anaerobic enrichment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Low-Dissolved-Oxygen Nitrifying Systems Exploit Ammonia-Oxidizing Bacteria with Unusually High Yields▿

PubMed Central

Bellucci, Micol; Ofiţeru, Irina D.; Graham, David W.; Head, Ian M.; Curtis, Thomas P.

2011-01-01

In wastewater treatment plants, nitrifying systems are usually operated with elevated levels of aeration to avoid nitrification failures. This approach contributes significantly to operational costs and the carbon footprint of nitrifying wastewater treatment processes. In this study, we tested the effect of aeration rate on nitrification by correlating ammonia oxidation rates with the structure of the ammonia-oxidizing bacterial (AOB) community and AOB abundance in four parallel continuous-flow reactors operated for 43 days. Two of the reactors were supplied with a constant airflow rate of 0.1 liter/min, while in the other two units the airflow rate was fixed at 4 liters/min. Complete nitrification was achieved in all configurations, though the dissolved oxygen (DO) concentration was only 0.5 ± 0.3 mg/liter in the low-aeration units. The data suggest that efficient performance in the low-DO units resulted from elevated AOB levels in the reactors and/or putative development of a mixotrophic AOB community. Denaturing gel electrophoresis and cloning of AOB 16S rRNA gene fragments followed by sequencing revealed that the AOB community in the low-DO systems was a subset of the community in the high-DO systems. However, in both configurations the dominant species belonged to the Nitrosomonas oligotropha lineage. Overall, the results demonstrated that complete nitrification can be achieved at low aeration in lab-scale reactors. If these findings could be extended to full-scale plants, it would be possible to minimize the operational costs and greenhouse gas emissions without risk of nitrification failure. PMID:21926211

Structure of nitrogen-converting communities induced by hydraulic retention time and COD/N ratio in constantly aerated granular sludge reactors treating digester supernatant.

PubMed

Cydzik-Kwiatkowska, Agnieszka; Rusanowska, Paulina; Zielińska, Magdalena; Bernat, Katarzyna; Wojnowska-Baryła, Irena

2014-02-01

This study investigated how hydraulic retention time (HRT) and COD/N ratio affect nitrogen-converting consortia in constantly aerated granules treating high-ammonium digester supernatant. Three HRTs (10, 13, 19 h) were tested at COD/N ratios of 4.5 and 2.3. Denaturing gradient gel electrophoresis and relative real-time PCR were used to characterize the microbial communities. When changes in HRT and COD/N increased nitrogen loading, the ratio of the relative abundance of aerobic to anaerobic ammonium-oxidizers decreased. The COD/N ratio determined the species composition of the denitrifiers; however, Thiobacillus denitrificans, Pseudomonas denitrificans and Azoarcus sp. showed a high tolerance to the environmental conditions and occurred in the granules from all reactors. Denitrifier genera that support granule formation were identified, such as Pseudomonas, Shinella, and Flavobacterium. In aerated granules, nirK-possessing bacteria were more diverse than nirS-possessing bacteria. At a low COD/N ratio, N2O-reducer diversity increased because of the presence of bacteria known as aerobic denitrifiers. Copyright © 2013 Elsevier Ltd. All rights reserved.

Flow field prediction in full-scale Carrousel oxidation ditch by using computational fluid dynamics.

PubMed

Yang, Yin; Wu, Yingying; Yang, Xiao; Zhang, Kai; Yang, Jiakuan

2010-01-01

In order to optimize the flow field in a full-scale Carrousel oxidation ditch with many sets of disc aerators operating simultaneously, an experimentally validated numerical tool, based on computational fluid dynamics (CFD), was proposed. A full-scale, closed-loop bioreactor (Carrousel oxidation ditch) in Ping Dingshan Sewage Treatment Plant in Ping Dingshan City, a medium-sized city in Henan Province of China, was evaluated using CFD. Moving wall model was created to simulate many sets of disc aerators which created fluid motion in the ditch. The simulated results were acceptable compared with the experimental data and the following results were obtained: (1) a new method called moving wall model could simulate the flow field in Carrousel oxidation ditch with many sets of disc aerators operating simultaneously. The whole number of cells of grids decreased significantly, thus the calculation amount decreased, and (2) CFD modeling generally characterized the flow pattern in the full-scale tank. 3D simulation could be a good supplement for improving the hydrodynamic performance in oxidation ditch designs.

Experimental and CFD-PBM approach coupled with a simplified dynamic analysis of mass transfer in phenol biodegradation in a three phase system of an aerated two-phase partitioning bioreactor for environmental applications

NASA Astrophysics Data System (ADS)

Moradkhani, Hamed; Anarjan Kouchehbagh, Navideh; Izadkhah, Mir-Shahabeddin

2017-03-01

A three-dimensional transient modeling of a two-phase partitioning bioreactor, combining system hydrodynamics, two simultaneous mass transfer and microorganism growth is modeled using computational fluid dynamics code FLUENT 6.2. The simulation is based on standard "k-ɛ" Reynolds-averaged Navier-Stokes model. Population balance model is implemented in order to describe gas bubble coalescence, breakage and species transport in the reaction medium and to predict oxygen volumetric mass transfer coefficient (kLa). Model results are verified against experimental data and show good agreement as 13 classes of bubble size is taking into account. Flow behavior in different operational conditions is studied. Almost at all impeller speeds and aeration intensities there were acceptable distributions of species caused by proper mixing. The magnitude of dissolved oxygen percentage in aqueous phase has a direct correlation with impeller speed and any increasing of the aeration magnitude leads to faster saturation in shorter periods of time.

Membrane-aerated biofilm reactor for the removal of 1,2-dichloroethane by Pseudomonas sp. strain DCA1.

PubMed

Hage, J C; Van Houten, R T; Tramper, J; Hartmans, S

2004-06-01

A membrane-aerated biofilm reactor (MBR) with a biofilm of Pseudomonas sp. strain DCA1 was studied for the removal of 1,2-dichloroethane (DCA) from water. A hydrophobic membrane was used to create a barrier between the liquid and the gas phase. Inoculation of the MBR with cells of strain DCA1 grown in a continuous culture resulted in the formation of a stable and active DCA-degrading biofilm on the membrane. The maximum removal rate of the MBR was reached at a DCA concentration of approximately 80 micro M. Simulation of the DCA fluxes into the biofilm showed that the MBR performance at lower concentrations was limited by the DCA diffusion rate rather than by kinetic constraints of strain DCA1. Aerobic biodegradation of DCA present in anoxic water could be achieved by supplying oxygen solely from the gas phase to the biofilm grown on the liquid side of the membrane. As a result, direct aeration of the water, which leads to undesired coagulation of iron oxides, could be avoided.

Sustained Aeration of Infant Lungs (SAIL) trial: study protocol for a randomized controlled trial.

PubMed

Foglia, Elizabeth E; Owen, Louise S; Thio, Marta; Ratcliffe, Sarah J; Lista, Gianluca; Te Pas, Arjan; Hummler, Helmut; Nadkarni, Vinay; Ades, Anne; Posencheg, Michael; Keszler, Martin; Davis, Peter; Kirpalani, Haresh

2015-03-15

Extremely preterm infants require assistance recruiting the lung to establish a functional residual capacity after birth. Sustained inflation (SI) combined with positive end expiratory pressure (PEEP) may be a superior method of aerating the lung compared with intermittent positive pressure ventilation (IPPV) with PEEP in extremely preterm infants. The Sustained Aeration of Infant Lungs (SAIL) trial was designed to study this question. This multisite prospective randomized controlled unblinded trial will recruit 600 infants of 23 to 26 weeks gestational age who require respiratory support at birth. Infants in both arms will be treated with PEEP 5 to 7 cm H2O throughout the resuscitation. The study intervention consists of performing an initial SI (20 cm H20 for 15 seconds) followed by a second SI (25 cm H2O for 15 seconds), and then PEEP with or without IPPV, as needed. The control group will be treated with initial IPPV with PEEP. The primary outcome is the combined endpoint of bronchopulmonary dysplasia or death at 36 weeks post-menstrual age. www.clinicaltrials.gov , Trial identifier NCT02139800 , Registered 13 May 2014.

Recovery strategies for tackling the impact of phenolic compounds in a UASB reactor treating coal gasification wastewater.

PubMed

Wang, Wei; Han, Hongjun

2012-01-01

The impact of phenolic compounds (around 3.2 g/L) resulted in a completely failed performance in a mesophilic UASB reactor treating coal gasification wastewater. The recovery strategies, including extension of HRT, dilution, oxygen-limited aeration, and addition of powdered activated carbon were evaluated in batch tests, in order to obtain the most appropriate way for the quick recovery of the failed reactor performance. Results indicated that addition of powdered activated carbon and oxygen-limited aeration were the best recovery strategies in the batch tests. In the UASB reactor, addition of powdered activated carbon of 1 g/L shortened the recovery time from 25 to 9 days and oxygen-limited aeration of 0-0.5 mgO2/L reduced the recovery time to 17 days. Reduction of bioavailable concentration of phenolic compounds and recovery of sludge activity were the decisive factors for the recovery strategies to tackle the impact of phenolic compounds in anaerobic treatment of coal gasification wastewater. Copyright © 2011 Elsevier Ltd. All rights reserved.

Galvanic corrosion of nitinol under deaerated and aerated conditions.

PubMed

Pound, Bruce G

2016-10-01

Various studies have examined the corrosion rate of nitinol generally under deaerated conditions. Likewise, galvanic corrosion studies have typically involved deaerated solutions. This work addressed the effect of galvanic coupling on the corrosion current of electropolished nitinol in phosphate buffered saline and 0.9% sodium chloride under dearated and aerated conditions for times up to 24 h. Tests were performed on nitinol alone and coupled with MP35N in both the mechanically polished and passivated conditions. Aeration and galvanic coupling were found to have relatively little effect, indicating that the corrosion current is controlled by the anodic reaction. The current can be attributed entirely to Ni(2+) dissolution, which appears to be governed by solid-state mass transport of Ni(2+) through the passive oxide film. Because corrosion of EP nitinol is controlled by the anodic reaction, contact between EP nitinol and MP35N or other biomedical Co-Cr alloys is unlikely to result in significant galvanic effects in vivo. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1322-1327, 2016. © 2015 Wiley Periodicals, Inc.

Analysis of the efficiency of recombinant Escherichia coli strain cultivation in a gas-vortex bioreactor.

PubMed

Savelyeva, Anna V; Nemudraya, Anna A; Podgornyi, Vladimir F; Laburkina, Nadezhda V; Ramazanov, Yuriy A; Repkov, Andrey P; Kuligina, Elena V; Richter, Vladimir A

2017-09-01

The levels of aeration and mass transfer are critical parameters required for an efficient aerobic bioprocess, and directly depend on the design features of exploited bioreactors. A novel apparatus, using gas vortex for aeration and mass transfer processes, was constructed in the Center of Vortex Technologies (Novosibirsk, Russia). In this paper, we compared the efficiency of recombinant Escherichia coli strain cultivation using novel gas-vortex technology with conventional bioprocess technologies such as shake flasks and bioreactors with mechanical stirrers. We demonstrated that the system of aeration and agitation used in gas-vortex bioreactors provides 3.6 times higher volumetric oxygen transfer coefficient in comparison with mechanical bioreactor. The use of gas-vortex bioreactor for recombinant E. coli strain cultivation allows to increase the efficiency of target protein expression at 2.2 times for BL21(DE3)/pFK2 strain and at 3.5 times for auxotrophic C600/pRT strain (in comparison with stirred bioreactor). © 2016 International Union of Biochemistry and Molecular Biology, Inc.

Operation optimization of a photo-sequencing batch reactor for wastewater treatment: Study on influencing factors and impact on symbiotic microbial ecology.

PubMed

Ye, Jianfeng; Liang, Junyu; Wang, Liang; Markou, Giorgos; Jia, Qilong

2018-03-01

Wastewater treatment technology with better energy efficiency and recyclability is in urgent demand. Photo-Sequencing batch reactor (SBR), which introduces microalgae into conventional SBR, is considered to have more potential for resource recycling. In this study, a photo-SBR was evaluated through the manipulation of several key operational parameters, i.e., aeration strength, light supply intensity and time per cycle, and solid retention time (SRT). The algal-bacterial symbiotic system had the potential of removing COD, NH 4 + -N and TN with limited aeration, representing the advantage of energy-saving by low aeration requirement. Maintaining appropriate proportion of microalgae in the symbiotic system is critical for good system performance. Introducing microalgae into conventional SBR has obvious impact on the original microbial ecology. When the concentration of microalgae is too high (>4.60 mg Chl/L), the inhibition on certain phyla of bacteria, e.g., Bacteroidetes and Actinobacteria, would become prominent and not conducive to the stable operation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Activated sludge mass reduction and biodegradability of the endogenous residues by digestion under different aerobic to anaerobic conditions: Comparison and modeling.

PubMed

Martínez-García, C G; Fall, C; Olguín, M T

2016-03-01

This study was performed to identify suitable conditions for the in-situ reduction of excess sludge production by intercalated digesters in recycle-activated sludge (RAS) flow. The objective was to compare and model biological sludge mass reduction and the biodegradation of endogenous residues (XP) by digestion under hypoxic, aerobic, anaerobic, and five intermittent-aeration conditions. A mathematical model based on the heterotrophic endogenous decay constant (bH) and including the biodegradation of XP was used to fit the long-term data from the digesters to identify and estimate the parameters. Both the bH constant (0.02-0.05 d(-1)) and the endogenous residue biodegradation constant (bP, 0.001-0.004 d(-1)) were determined across the different mediums. The digesters with intermittent aeration cycles of 12 h-12 h and 5 min-3 h (ON/OFF) were the fastest, compared to the aerobic reactor. The study provides a basis for rating RAS-digester volumes to avoid the accumulation of XP in aeration tanks. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of micro-aeration and inoculum type on the biodegradation of lignocellulosic substrate.

PubMed

Tsapekos, P; Kougias, P G; Vasileiou, S A; Lyberatos, G; Angelidaki, I

2017-02-01

The effect of various micro-aeration strategies on the anaerobic digestion (AD) of wheat straw was thoroughly examined using a mixture of inocula, containing compost and well digested sludge from biogas plant. The aim was to determine the most efficient oxygen load, pulse repetition and treatment duration, resulting in the highest methane production. The oxygen load had the largest impact on the biodegradability of straw, among the examined variables. More specifically, a micro-aeration intensity of 10mLO 2 /gVS was identified as the critical threshold above which the AD performance was more susceptible to instability. The highest enhancement in biogas production was achieved by injecting 5mLO 2 /gVS for a consecutive 3-day treatment period, presenting a 7.2% increase compared to the untreated wheat straw. Nevertheless, the results from optimisation case study indicated a higher increase of 9% by injecting 7.3mLO 2 /gVS, distributed in 2 pulses during a slightly shorter treatment period (i.e. 47h). Copyright © 2016 Elsevier Ltd. All rights reserved.

Strategies for enhanced deammonification performance and reduced nitrous oxide emissions.

PubMed

Leix, Carmen; Drewes, Jörg E; Ye, Liu; Koch, Konrad

2017-07-01

Deammonification's performance and associated nitrous oxide emissions (N 2 O) depend on operational conditions. While studies have investigated factors for high performances and low emissions separately, this study investigated optimizing deammonification performance while simultaneously reducing N 2 O emissions. Using a design of experiment (DoE) method, two models were developed for the prediction of the nitrogen removal rate and N 2 O emissions during single-stage deammonification considering three operational factors (i.e., pH value, feeding and aeration strategy). The emission factor varied between 0.7±0.5% and 4.1±1.2% at different DoE-conditions. The nitrogen removal rate was predicted to be maximized at settings of pH 7.46, intermittent feeding and aeration. Conversely, emissions were predicted to be minimized at the design edges at pH 7.80, single feeding, and continuous aeration. Results suggested a weak positive correlation between the nitrogen removal rate and N 2 O emissions, thus, a single optimizing operational set-point for maximized performance and minimized emissions did not exist. Copyright © 2017 Elsevier Ltd. All rights reserved.

Control of partial nitrification using pulse aeration for treating digested effluent of swine wastewater.

PubMed

Wang, Shuang; Deng, Liangwei; Zheng, Dan; Wang, Lan; Zhang, Yunhong; Yang, Hongnan; Jiang, Yiqi; Huang, Fangyu

2018-04-22

Three sequencing batch reactors (SBRs) were used to investigate the influence of pulse frequencies on the partial nitrification (PN) process in this study. At a total aeration time of 6 min each hour, the aerated frequencies of R1, R2 and R3 were 6, 3 and 2 time h -1 . During the steady period (117-143d), the nitrite accumulation rates (NARs) were 90.80%, 90.71% and 90.23% in R1, R2 and R3, respectively, indicating a steady nitritation was acquired. Activity measurements of the sludge samples taken at day 138 showed the activity of nitrite oxidating bacteria (NOB) was 0, indicating NOBs were successfully suppressed. The ratio of NO 2 - -N to NH 4 + -N in the effluent of R3 was 1.35, which most closely matched the influent of Anammox process. However, the energy efficiency evaluation showed that R1 had the highest actual oxygen transfer efficiency (AOTE) and dynamical efficiency (DE). Copyright © 2018 Elsevier Ltd. All rights reserved.

Application of sewage sludge and intermittent aeration strategy to the bioremediation of DDT- and HCH-contaminated soil.

PubMed

Liang, Qi; Lei, Mei; Chen, Tongbin; Yang, Jun; Wan, Xiaoming; Yang, Sucai

2014-08-01

Adding organic amendments to stimulate the biodegradation of pesticides is a subject of ongoing interest. The effect of sewage sludge on the bioremediation of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) contaminated soil was investigated in bench scale experiments, and intermittent aeration strategy was also used in this study to form an anaerobic-aerobic cycle. Bioremediation of DDT and HCH was enhanced with the addition of sewage sludge and the intermittent aeration. The removal rates of HCH and DDT were raised by 16.8%-80.8% in 10 days. Sewage sludge increased the organic carbon content from 6.2 to 218 g/kg, and it could also introduce efficient degradation microbes to soil, including Pseudomonas sp., Bacillus sp. and Sphingomonas sp. The unaerated phase enhanced the anaerobic dechlorination of DDT and HCH, and anaerobic removal rates of β-HCH, o,p'-DDT and p,p'-DDT accounted for more than 50% of the total removal rates, but the content of α-HCH declined more in the aerobic phase. Copyright © 2014. Published by Elsevier B.V.

Can airborne ultrasound monitor bubble size in chocolate?

NASA Astrophysics Data System (ADS)

Watson, N.; Hazlehurst, T.; Povey, M.; Vieira, J.; Sundara, R.; Sandoz, J.-P.

2014-04-01

Aerated chocolate products consist of solid chocolate with the inclusion of bubbles and are a popular consumer product in many countries. The volume fraction and size distribution of the bubbles has an effect on their sensory properties and manufacturing cost. For these reasons it is important to have an online real time process monitoring system capable of measuring their bubble size distribution. As these products are eaten by consumers it is desirable that the monitoring system is non contact to avoid food contaminations. In this work we assess the feasibility of using an airborne ultrasound system to monitor the bubble size distribution in aerated chocolate bars. The experimental results from the airborne acoustic experiments were compared with theoretical results for known bubble size distributions using COMSOL Multiphysics. This combined experimental and theoretical approach is used to develop a greater understanding of how ultrasound propagates through aerated chocolate and to assess the feasibility of using airborne ultrasound to monitor bubble size distribution in these systems. The results indicated that a smaller bubble size distribution would result in an increase in attenuation through the product.

Effect of dissolved oxygen on biological denitrification using biodegradable plastic as the carbon source

NASA Astrophysics Data System (ADS)

Zhang, Xucai; Zhang, Jianmei

2018-02-01

Biological denitrification is currently a common approach to remove nitrate from wastewater. This study was conducted to evaluate the influence of dissolved oxygen on denitrification in wastewater treatment using biodegradable plastic as carbon source by designing the aerated, anoxic, and low-oxygen experimental treatment groups. The results showed that the removal rates of nitrate in anoxic and low-oxygen groups were 30.6 g NO3 --Nm-3 d-1 and 30.8 g NO3 --N m-3 d-1 at 83 h, respectively, both of which were higher than that of the aerated group. There was no significant difference between the anoxic and low-oxygen treatment groups for the nitrate removal. Additional, the nitrite accumulated during the experiments, and the nitrite concentrations in anoxic and aerated groups were lower than those in low-oxygen group. No nitrite was detected in all groups at the end of the experiments. These findings indicated that dissolved oxygen has important influence on denitrification, and anoxic and low-oxygen conditions can support completely denitrification when using BP as carbon source in nitrate-polluted wastewater treatment.

Development and implementation of an expert system to improve the control of nitrification and denitrification in the Vic wastewater treatment plant.

PubMed

Ribas, F; Rodríguez-Roda, I; Serrat, J; Clara, P; Comas, J

2008-05-01

Wastewater treatment plants employ various physical, chemical and biological processes to reduce pollutants from raw wastewater. One of the most important is the biological nitrogen removal process through nitrification and denitrification steps taking place in various sections of the biological reactor. One of the most extensively used configurations to achieve the biological nitrogen removal is an activated sludge system using oxidation ditch or extended aeration. To improve nitrogen removal in the wastewater treatment plant (WWTP) of Vic (Catalonia, NE Spain), the automatic aeration control system was complemented with an Expert System to always provide the most appropriate aeration or anoxia sequence based on the values of ammonium and nitrates given by an automatic analyzer. This article illustrates the development and implementation of this knowledge-based system within the framework of a Decision Support System, which performs SCADA functions. The paper also shows that the application of the decision support system in the Vic WWTP resulted in significant improvements to the biological nitrogen removal.

Interannual and long-term changes in the trophic state of a multibasin lake: Effects of morphology, climate, winter aeration, and beaver activity

USGS Publications Warehouse

Robertson, Dale M.; Rose, William; Reneau, Paul C.

2016-01-01

Little St. Germain Lake (LSG), a relatively pristine multibasin lake in Wisconsin, USA, was examined to determine how morphologic (internal), climatic (external), anthropogenic (winter aeration), and natural (beaver activity) factors affect the trophic state (phosphorus, P; chlorophyll, CHL; and Secchi depth, SD) of each of its basins. Basins intercepting the main flow and external P sources had highest P and CHL and shallowest SD. Internal loading in shallow, polymictic basins caused P and CHL to increase and SD to decrease as summer progressed. Winter aeration used to eliminate winterkill increased summer internal P loading and decreased water quality, while reductions in upstream beaver impoundments had little effect on water quality. Variations in air temperature and precipitation affected each basin differently. Warmer air temperatures increased productivity throughout the lake and decreased clarity in less eutrophic basins. Increased precipitation increased P in the basins intercepting the main flow but had little effect on the isolated deep West Bay. These relations are used to project effects of future climatic changes on LSG and other temperate lakes.

Distribution and characterization of anammox in a swine wastewater activated sludge facility.

PubMed

Yamagishi, Takao; Takeuchi, Mio; Wakiya, Yuichiro; Waki, Miyoko

2013-01-01

Anaerobic ammonium oxidation (anammox) is a novel biological nitrogen removal process that oxidizes NH4(+) to N2 with NO2(-) as an electron acceptor. The purpose of this study was to examine the potential activity and characteristics of anammox in a conventional swine wastewater treatment facility, which uses an activated sludge system consisting of three cascade aeration tanks equipped with ceramic support material. Anammox activity was estimated by a (15)N tracer assay method and was detected in all the sludge and biofilm samples in each aeration tank. Biofilm taken from the third aeration tank, in which the dissolved oxygen concentration was 7.5 mg/L and the wastewater included a high concentration of NO3(-), showed by far the highest anammox activity. A clone library analysis showed the existence of anammox bacteria closely related to 'Candidatus Jettenia asiatica' and 'Ca. Brocadia caroliniensis'. The optimum conditions for anammox activity were a pH of 6.7-7.2, a temperature of 35 °C, a NO2(-) concentration of 10 mmol/L or less, and an NH4(+) concentration of 32 mmol/L or less.

[Influence of glucose and galactose on the morphology and biological properties of Yersinia pseudotuberculosis].

PubMed

Bakholdina, S I; Solov'eva, T F; Shubin, F N; Timchenko, N F

2005-01-01

When cultivated in the presence of glucose, irrespective of temperature and the degree of aeration, Y. pseudotuberculosis cells have the ovoid form, constant size and low hydrophobic properties of their surface. Meanwhile the characteristics of the bacteria grown in the medium, carbohydrate-free or with galactose added, essentially depend on the conditions of medium aeration. Under the conditions of intensive stirring at both temperatures these bacteria acquire the coccoid form, not typical for Yersinia, they have a smaller area (approximately 2 times) and more hydrophobic surface in comparison with the cells grown in the presence of glucose. Under stationary conditions the differences between the cells, cultivated in the presence of galactose and glucose, in form and area disappear, but the differences in the hydrophobic properties of the surface are retained. As revealed in this study, the cells grown in the presence of galactose and under the conditions of intensive medium stirring, in contrast to those grown with glucose, have 1.5-fold greater invasive activity, irrespective of aeration conditions, eightfold greater resistance to ampicillin and twofold greater resistance to streptomycin and erythromycin.

Toxic effects of ethylene oxide residues on bovine embryos in vitro.

PubMed

Holyoak, G R; Wang, S; Liu, Y; Bunch, T D

1996-04-15

The potential of ethylene oxide (EtO) residues in exposed plastic tissue culture dishes to adversely affect bovine oocyte maturation, fertilization and subsequent embryonic development was monitored. In experiment 1, the effects of aeration time and aeration combined with washing of EtO-gassed culture dishes on the extent of residual toxicity were investigated. There was no cleavage in any treatment in which oocytes were matured and fertilized in dishes exposed to EtO. EtO residues caused functional degeneration of oocytes even when culture dishes were aerated for more than 12 days post EtO-exposure and repeatedly washed. In experiment 2, the residual toxicity of EtO gas on in vitro maturation (IVM), in vitro fertilization (IVF) and in vitro culture (IVC) were evaluated. Cleavage rate significantly decreased and post-cleavage development was retarded in ova maintained in dishes treated with EtO either during IVM or IVF. EtO residues may be more detrimental to spermatozoa than to oocytes which may have been the primary cause of fertilization failure during IVF.

Technical potential of microalgal bacterial floc raceway ponds treating food-industry effluents while producing microalgal bacterial biomass: An outdoor pilot-scale study.

PubMed

Van Den Hende, Sofie; Beelen, Veerle; Julien, Lucie; Lefoulon, Alexandra; Vanhoucke, Thomas; Coolsaet, Carlos; Sonnenholzner, Stanislaus; Vervaeren, Han; Rousseau, Diederik P L

2016-10-01

To replace costly mechanical aeration by photosynthetical aeration, upflow anaerobic sludge blanket (UASB) effluent of food-industry was treated in an outdoor MaB-floc raceway pond. Photosynthetic aeration was sufficient for nitrification, but the raceway effluent quality was below current discharge limits, despite the high hydraulic retention time (HRT) of 35days. Hereafter, conventional activated sludge (CAS) effluent of food-industry was treated in this pond to recover phosphorus. The two-day HRT results in a more realistic pond area, but the phosphorus removal efficiency was low (20%). High biomass productivities were obtained, i.e. 31.3 and 24.9ton total suspended solids hapond(-1)year(-1) for UASB and CAS effluent, respectively. Bioflocculation enabled successful harvesting of CAS effluent-fed MaB-flocs by settling and filtering at 150-250μm to 22.7% total solids. To conclude, MaB-floc raceway ponds cannot be recommended as the sole treatment for these food-industry effluents, but huge potential lies in added-value biomass production. Copyright © 2016 Elsevier Ltd. All rights reserved.

Functioning of microbial complexes in aerated layers of a highmoor peat bog

NASA Astrophysics Data System (ADS)

Golovchenko, A. V.; Bogdanova, O. Yu.; Stepanov, A. L.; Polyanskaya, L. M.; Zvyagintsev, D. G.

2010-09-01

Monitoring was carried out using the luminescent-microscopic method of the abundance parameters of different groups of microorganisms in a monolith and in the mixed layers of a highmoor peat bog (oligotrophic residual-eutrophic peat soil) in a year-long model experiment. The increase of the aeration as a result of mixing of the layers enhanced the activity of the soil fungi. This was attested to by the following changes: the increase of the fungal mycelium length by 6 times and of the fungal biomass by 4 times and the double decrease of the fraction of spores in the fungal complex. The response of the fungal complex to mixing was different in the different layers of the peat bog. The maximal effect was observed in the T1 layer and the minimal one in the T2 layer. The emission of CO2 in the mixed samples was 1.5-2 times higher than that from the undisturbed peat samples. In contrast with the fungi, the bacteria and actinomycetes were not affected by the aeration of the highmoor layers.

Impact of oxygen on the coexistence of nitrification, denitrification, and sulfate reduction in oxygen-based membrane aerated biofilm.

PubMed

Liu, Hong; Tan, Shuying; Sheng, Zhiya; Yu, Tong; Liu, Yang

2015-03-01

Membrane aerated biofilms (MABs) are subject to "counter diffusion" of oxygen and substrates. In a membrane aerated biofilm reactor, gases (e.g., oxygen) diffuse through the membrane into the MAB, and liquid substrates pass from the bulk liquid into the MAB. This behavior can result in a unique biofilm structure in terms of microbial composition, distribution, and community activity in the MAB. Previous studies have shown simultaneous aerobic oxidation, nitrification, and denitrification within a single MAB. Using molecular techniques, we investigated the growth of sulfate-reducing bacteria (SRB) in the oxygen-based MAB attached to a flat sheet membrane. Denaturing gradient gel electrophoresis of the amplified 16S rRNA gene fragments and functional gene fragments specific for ammonia-oxidizing bacteria (amoA), denitrifying bacteria (nirK), and SRB (dsrB) demonstrated the coexistence of nitrifiers, denitrifiers, and SRB communities within a single MAB. The functional diversities of SRB and denitrifiers decreased with an increase in the oxygen concentration in the bulk water of the reactor.

Membrane properties change in fine-pore aeration diffusers: full-scale variations of transfer efficiency and headloss.

PubMed

Rosso, Diego; Libra, Judy A; Wiehe, Wolfgang; Stenstrom, Michael K

2008-05-01

Fine-pore diffusers are the most common aeration system in municipal wastewater treatment. Punched polymeric membranes are often used in fine-pore aeration due to their advantageous initial performance. These membranes are subject to fouling and scaling, resulting in increased headloss and reduced oxygen transfer efficiency, both contributing to increased plant energy costs. This paper describes and discusses the change in material properties for polymeric fine-pore diffusers, comparing new and used membranes. Three different diffuser technologies were tested and sample diffusers from two wastewater treatment facilities were analysed. The polymeric membranes analysed in this paper were composed of ethylene-propylene-diene monomer (EPDM), polyurethane, and silicon. Transfer efficiency is usually lower with longer times in operation, as older, dilated orifices produce larger bubbles, which are unfavourable to mass transfer. At the same time, headloss increases with time in operation, since membranes increase in rigidity and hardness, and fouling and scaling phenomena occur at the orifice opening. Change in polymer properties and laboratory test results correlate with the decrease in oxygen transfer efficiency.

Inhalation Injury: Pathophysiology and Clinical Care. Proceedings of a Symposium Conducted at the Trauma Institute of San Antonio, San Antonio, TX, USA on 28 March 2006

DTIC Science & Technology

2007-01-01

the Hounsfield - unit ranges established by Gattinoni et al. [23] (air: hyperinflated, normal, poorly aerated, and non-aerated lung). The fraction of...T. J., Wolf S. E., 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) United States Army...Abnormally low V/Q is ɘ.1 and abnormally high is V/Q > 10. Shunt is specified as blood flow in units with V/Q < 0.005 and dead space as ventilation

Development of a New Specification for Aircraft Catapult Lubricant, LA7, NSN 9150-01-430-2884

DTIC Science & Technology

2013-09-30

hours, run at 95C in the presence of water and an iron - copper catalyst. It is mainly used to assess oils used in circulating oil systems. The test is...and an iron -copper catalyst and is terminated when the total acid number reaches a value of 2.0 mg KOH/g with the number of test hours at that point...Tendency/Stability ASTM D 892 Seq. 1 Aerated Vol., mL, Max 50 Vol. after 10 min, mL, Max 0 Seq. II Aerated Vol., mL, Max 50

Materials and Technologies Used in Wastewater Treatment

NASA Astrophysics Data System (ADS)

Moga, I. C.; Ardelean, I.; Donțu, O. G.; Moisescu, C.; Băran, N.; Petrescu, G.; Voicea, I.

2018-06-01

The biological wastewater treatment is based on biofilms activity. The biofilms can be fixed on biofilm carriers, that are made from varied materials, but most of them are made from high density polyethylene. The authors propose other mixtures of varied materials to obtain an increased load of microorganisms on biofilm carriers. During the experiments the load of microorganisms was increased up to 250% compared to the load on polyethylene biofilm carriers. Also, for the aerated biological tanks an innovative aeration system made from stainless steel pipes with fine pores (<1 mm) realized by electro-erosion, is proposed.

Redox potential: An indicator of site productivity in forest management

NASA Astrophysics Data System (ADS)

Sajedi, Toktam; Prescott, Cindy; Lavkulich, Les

2010-05-01

Redox potential (Eh) is an integrated soil measurement that reflects several environmental conditions in the soil associated with aeration, moisture and carbon (organic matter) dynamics. Its measurement can be related to water table fluctuations, precipitation and landscape gradients, organic matter decomposition rates, nutrient dynamics, biological diversity and plant species distribution. Redox is an excellent indicator of soil biological processes, as it is largely a reflection of microbial activities which to a large extent govern carbon dynamics and nutrient cycling. Redox thus serves as an ecological indicator of site productivity at the ecosystem scale and may be used for management purposes as its magnitude can be altered by activities such as harvesting and drainage. A threshold value of 300 mv has been documented as the critical value below which anaerobic conditions in the soil develop. However, redox measurements and its impacts on ecosystem processes such as nutrient cycling and productivity, especially in forest ecosystems, have not received the attention that this "master" variable deserves, On northern Vancouver Island, Canada, regenerating stands of western redcedar-western hemlock (CH) sites exhibit symptoms of nutrient deficiencies and slow growth, but this phenomenon does not occur on adjacent western hemlock- amabalis fir (HA) sites. We tested the hypothesis that differences in nutrient supply and distribution of plant species was caused by differences in moisture regime and redox potential. Redox potential, pH, soil aeration depth (steel rods), organic matter thickness, bulk density, soil carbon store, plant species distribution and richness were measured at five old-growth and five 10-year-old cutover blocks. Results of investigations confirmed that CH forests were wetter, had redox values lower than the critical 300mv and a shallower aerated zone, compared with adjacent regenerating HA sites. Fifty percent of the CH plots had redox values less than +300 mv in the forest floor; whereas only 15 percent of the HA plots had such low values. Composition of the forest understory species was related to soil moisture/aeration. Soil aeration was the most important soil variable influencing plant species composition, explaining 25% of the plant community variability. Eh was always greater than +300 mv in the mineral soil of old growth HA forests but below +300 mv in HA clearcuts, suggesting paludification; however it was below or at this threshold in both CH forests and clearcuts. The reduction in measured redox without a noticeable change in the watertable in HA sites suggests that harvesting HA forests shifts the ecosystem towards more anaerobic conditions more similar to CH sites. In a complimentary study, the significance of redox was assessed in a cedar swamp cutover by exploring the relationships between soil redox potential and tree growth, and mineralization of C and soil C store along a gradient of moisture caused by drainage. Drainage improved aeration in the rooting zone, expressed as redox, and above- and below ground C storage; however C mineralization measured as CO2 evolution was not affected. Tree growth was positively correlated with redox potential. Our results indicate that drainage could be a useful silvicultural practice for improving the productivity of these ecosystems and that it may be possible to improve tree growth without stimulating loss of soil C. This requires that drainage improve aeration in the rooting zone while maintaining redox levels of less than +300 mV in the bulk soil, indicating that redox measurements should be incorporated into silviculture interventions to improve productivity of these forests.

Passive aeration composting of chicken litter: effects of aeration pipe orientation and perforation size on losses of compost elements.

PubMed

Ogunwande, Gbolabo A; Osunade, James A

2011-01-01

A passive aeration composting study was undertaken to investigate the effects of aeration pipe orientation (PO) and perforation size (PS) on some physico-chemical properties of chicken litter (chicken manure + sawdust) during composting. The experimental set up was a two-factor completely randomised block design with two pipe orientations: horizontal (Ho) and vertical (Ve), and three perforation sizes: 15, 25 and 35 mm diameter. The properties monitored during composting were pile temperature, moisture content (MC), pH, electrical conductivity (EC), total carbon (C(T)), total nitrogen (N(T)) and total phosphorus (P(T)). Moisture level in the piles was periodically replenished to 60% for efficient microbial activities. The results of the study showed that optimum composting conditions (thermophilic temperatures and sanitation requirements) were attained in all the piles. During composting, both PO and PS significantly affected pile temperature, moisture level, pH, C(T) loss and P(T) gain. EC was only affected by PO while N(T) was affected by PS. Neither PO nor PS had a significant effect on the C:N ratio. A vertical pipe was effective for uniform air distribution, hence, uniform composting rate within the composting pile. The final values showed that PO of Ve and PS of 35 mm diameter resulted in the least loss in N(T). The PO of Ho was as effective as Ve in the conservation of C(T) and P(T). Similarly, the three PSs were equally effective in the conservation of C(T) and P(T). In conclusion, the combined effects of PO and PS showed that treatments Ve35 and Ve15 were the most effective in minimizing N(T) loss. Copyright © 2010 Elsevier Ltd. All rights reserved.

Effect of C/N ratio, aeration rate and moisture content on ammonia and greenhouse gas emission during the composting.

PubMed

Jiang, Tao; Schuchardt, Frank; Li, Guoxue; Guo, Rui; Zhao, Yuanqiu

2011-01-01

Gaseous emission (N2O, CH4 and NH3) from composting can be an important source of anthropogenic greenhouse gas and air pollution. A laboratory scale orthogonal experiment was conducted to estimate the effects of C/N ratio, aeration rate and initial moisture content on gaseous emission during the composting of pig faeces from Chinese Ganqinfen system. The results showed that about 23.9% to 45.6% of total organic carbon (TOC) was lost in the form of CO2 and 0.8% to 7.5% of TOC emitted as CH4. Most of the nitrogen was lost in the form of NH3, which account for 9.6% to 32.4% of initial nitrogen. N2O was also an important way of nitrogen losses and 1.5% to 7.3% of initial total nitrogen was lost as it. Statistic analysis showed that the aeration rate is the most important factor which could affect the NH3 (p = 0.0189), CH4 (p = 0.0113) and N2O (p = 0.0493) emissions significantly. Higher aeration rates reduce the CH4 emission but increase the NH3 and N2O losses. C/N ratio could affect the NH3 (p = 0.0442) and CH4 (p = 0.0246) emissions significantly, but not the N2O. Lower C/N ratio caused higher NH3 and CH4 emissions. The initial moisture content can not influence the gaseous emission significantly. Most treatments were matured after 37 days, except a trial with high moisture content and a low C/N ratio.

Sediment Resuspension and Deposition on Seagrass Leaves Impedes Internal Plant Aeration and Promotes Phytotoxic H2S Intrusion

PubMed Central

Brodersen, Kasper E.; Hammer, Kathrine J.; Schrameyer, Verena; Floytrup, Anja; Rasheed, Michael A.; Ralph, Peter J.; Kühl, Michael; Pedersen, Ole

2017-01-01

HIGHLIGHTS: Sedimentation of fine sediment particles onto seagrass leaves severely hampers the plants' performance in both light and darkness, due to inadequate internal plant aeration and intrusion of phytotoxic H2S. Anthropogenic activities leading to sediment re-suspension can have adverse effects on adjacent seagrass meadows, owing to reduced light availability and the settling of suspended particles onto seagrass leaves potentially impeding gas exchange with the surrounding water. We used microsensors to determine O2 fluxes and diffusive boundary layer (DBL) thickness on leaves of the seagrass Zostera muelleri with and without fine sediment particles, and combined these laboratory measurements with in situ microsensor measurements of tissue O2 and H2S concentrations. Net photosynthesis rates in leaves with fine sediment particles were down to ~20% of controls without particles, and the compensation photon irradiance increased from a span of 20–53 to 109–145 μmol photons m−2 s−1. An ~2.5-fold thicker DBL around leaves with fine sediment particles impeded O2 influx into the leaves during darkness. In situ leaf meristematic O2 concentrations of plants exposed to fine sediment particles were lower than in control plants and exhibited long time periods of complete meristematic anoxia during night-time. Insufficient internal aeration resulted in H2S intrusion into the leaf meristematic tissues when exposed to sediment resuspension even at relatively high night-time water-column O2 concentrations. Fine sediment particles that settle on seagrass leaves thus negatively affect internal tissue aeration and thereby the plants' resilience against H2S intrusion. PMID:28536583

[Laboratory evaluation of remediation of nitrobenzene contaminated aquifer by using groundwater circulation well].

PubMed

Bai, Jing; Zhao, Yong-Sheng; Sun, Chao; Qin, Chuan-Yu; Yu, Ling

2014-10-01

A two-dimension simulated sand box was set up to investigate the influencing factors, such as the initial groundwater level, aeration rate and the initial groundwater rate, that affect groundwater circulation well (GCW) by determining the intensity of groundwater circulation which was characterized by the variation of groundwater level before and after aeration. The optimal operating parameters were used to remediate nitrobenzene contaminated aquifer. The results demonstrated that: GCW could be well operated under the conditions of 45 cm groundwater level, 0.7 m3 · h(-1) aeration rate. The effects of groundwater velocity less than 1.0 m · d(-1) could be ignored. The lateral mobility rate of nitrobenzene was faster than that of longitudinal. The average concentration of nitrobenzene was 246.97 mg · L(-1) on day 50 of leakage. During the remediation of circulation well, an efficient organics remediation region was gradually formed around the circulation well. The organics in this region was removed preferentially, and the concentration decreased continuously. Besides the efficient remediation region, there was a transient region, where the concentration of organics was influenced by the combined effects of adsorption/desorption and migration potential of organics. During the whole remediation process, the concentration of nitrobenzene went through three stages described as rapid removal, slow removal. After 14h aeration, the nitrobenzene average concentration was reduced to 71.19 mg L(-1). The residual nitrobenzene was distributed in regions far away from GCW. Therefore, nitrobenzene contaminated aquifer could be well remediated by GCW, and there were optimal operation conditions and appropriate remediation time which guaranteed the best remediation effect.

Effects of Aeration of Sawdust Cultivation Bags on Hyphal Growth of Lentinula edodes.

PubMed

Lee, Hwa-Yong; Ham, Eun-Ju; Yoo, Young-Jin; Kim, Eui-Sung; Shim, Kyu-Kwang; Kim, Myung-Kon; Koo, Chang-Duck

2012-09-01

The effects of aeration through lid filters on the hyphal growth of Lentinula edodes (oak mushroom) in sawdust cultivation bags were investigated. The aeration treatment levels were traditional 27 mm hole cotton plugs, cotton balls and combinations of seven hole sizes × two hole positions (up and under) in the lids covering plastic bags containing 1.4 kg sawdust medium at 63% moisture that had been autoclaved for one hour and inoculated with sawdust spawn of L. edodes strain 921. Aeration treatment effects were measured based on the CO(2) concentration at the 15th wk, as well as the hyphal growth rate and degree of weight loss of bags every 14 days for 15 wk. In bags with traditional cotton plugs, the CO(2) concentration was 3.8 ± 1.3%, daily mean hyphal growth was 2.3 ± 0.6 mm and daily mean weight loss was 0.84 ± 0.26 g. In the bags with 15 mm diameter holes, the CO(2) concentration was 6.0 ± 1.6%, daily hyphal growth was 2.8 ± 0.2 mm and daily weight loss was 0.86 ± 0.4 g. The bags with 15 mm holes had a higher CO(2) concentration and lower water loss than bags with other hole sizes, but the hyphal growth was not significantly different from that of other bags. The weight loss of bags increased proportionally relative to the lid hole sizes. Taken together, these results indicate that traditional cotton plugs are economically efficient, but 15 mm hole lids are the most efficient at maintaining hyphal growth and controlling water loss while allowing CO(2) emissions.

The influence of process parameters in production of lipopeptide iturin A using aerated packed bed bioreactors in solid-state fermentation.

PubMed

Piedrahíta-Aguirre, C A; Bastos, R G; Carvalho, A L; Monte Alegre, R

2014-08-01

The strain Bacillus iso 1 co-produces the lipopeptide iturin A and biopolymer poly-γ-glutamic acid (γ-PGA) in solid-state fermentation of substrate consisting of soybean meal, wheat bran with rice husks as an inert support. The effects of pressure drop, oxygen consumption, medium permeability and temperature profile were studied in an aerated packed bed bioreactor to produce iturin A, diameter of which was 50 mm and bed height 300 mm. The highest concentrations of iturin A and γ-PGA were 5.58 and 3.58 g/kg-dry substrate, respectively, at 0.4 L/min after 96 h of fermentation. The low oxygen uptake rates, being 23.34 and 22.56 mg O2/kg-dry solid substrate for each air flow rate tested generated 5.75 W/kg-dry substrate that increased the fermentation temperature at 3.7 °C. The highest pressure drop was 561 Pa/m at 0.8 L/min in 24 h. This is the highest concentration of iturin A produced to date in an aerated packed bed bioreactor in solid-state fermentation. The results can be useful to design strategies to scale-up process of iturin A in aerated packed bed bioreactors. Low concentration of γ-PGA affected seriously pressure drop, decreasing the viability of the process due to generation of huge pressure gradients with volumetric air flow rates. Also, the low oxygenation favored the iturin A production due to the reduction of free void by γ-PGA production, and finally, the low oxygen consumption generated low metabolic heat. The results show that it must control the pressure gradients to scale-up the process of iturin A production.

Influence of anoxic pore water dissolved organic matter on the fate and transport of hydrophobic organic pollutants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunchak-Kariouk, K.

1992-01-01

Pore water dissolved organic matter is an overlooked pool of organic matter important to the environmental fate of hydrophobic organic pollutants. The association of polychlorinated biphenyls, polyaromatic hydrocarbons and chlorinated pesticides with pore water dissolved organic matter influences their distribution and mobility within the bottom sediment environment. Steep physical, biological and chemical gradients at the sediment/water interface isolate the pore water and create unique conditions within the sediment. This study indicates that any disturbance of this environment will alter the distribution and mobility of organic pollutants by changing their association to the pore water dissolved organic matter. A small volumemore » closed equilibration method was developed to measure the solubility enhancement of 2,2' 4,4'-tetrachlorobiphenyl (TeCB) by natural dissolved organic matter. Chemical coated micro-glass beads were equilibrated with anoxic and laboratory aerated (oxic) pore water samples in flame sealed ampules. The TeCB enhanced solubilities were used to determine the pore water dissolved organic matter partition coefficient, K[sub pwdom]. The measured TeCB solubility and K[sub pwdom] were much smaller for anoxic than oxic pore waters. The dissolved organic matter sorptive capacity for the TeCB increased as the water was aerated. This change is attributed to coagulative fractionation and structural changes of the pore water dissolved organic matter during aeration and was characterized by differences in the dissolved organic matter concentration, UV absorption at 254 nm, interfacial surface tension, and sorption capacity of molecular weight fractions of anoxic and oxic pore water dissolved organic matter. The increase in partitioning indicates that there will be an increase in the mobility of the TeCB as an anoxic bottom sediment environment is disturbed and aerated.« less

Laboratory studies to characterize the efficacy of sand capping a coal tar-contaminated sediment.

PubMed

Hyun, Seunghun; Jafvert, Chad T; Lee, Linda S; Rao, P Suresh C

2006-06-01

Placement of a microbial active sand cap on a coal tar-contaminated river sediment has been suggested as a cost effective remediation strategy. This approach assumes that the flux of contaminants from the sediment is sufficiently balanced by oxygen and nutrient fluxes into the sand layer such that microbial activity will reduce contaminant concentrations within the new benthic zone and reduce the contaminant flux to the water column. The dynamics of such a system were evaluated using batch and column studies with microbial communities from tar-contaminated sediment under different aeration and nutrient inputs. In a 30-d batch degradation study on aqueous extracts of coal tar sediment, oxygen and nutrient concentrations were found to be key parameters controlling the degradation rates of polycyclic aromatic hydrocarbons (PAHs). For the five PAHs monitored (naphthalene, fluorene, phenanthrene, anthracene, and pyrene), degradation rates were inversely proportional to molecular size. For the column studies, where three columns were packed with a 20-cm sand layer on the top of a 5 cm of sediment layer, flow was established to sand layers with (1) aerated water, (2) N(2) sparged water, or (3) HgCl(2)-sterilized N(2) sparged water. After steady-state conditions, PAH concentrations in effluents were the lowest in the aerated column, except for pyrene, whose concentration was invariant with all effluents. These laboratory scale studies support that if sufficient aeration can be achieved in the field through either active and passive means, the resulting microbially active sand layer can improve the water quality of the benthic zone and reduce the flux of many, but not all, PAHs to the water column.

Influence of Iron and Aeration on Staphylococcus aureus Growth, Metabolism, and Transcription

PubMed Central

Ledala, Nagender; Zhang, Bo; Seravalli, Javier; Powers, Robert

2014-01-01

Staphylococcus aureus is a prominent nosocomial pathogen and a major cause of biomaterial-associated infections. The success of S. aureus as a pathogen is due in part to its ability to adapt to stressful environments. As an example, the transition from residing in the nares to residing in the blood or deeper tissues is accompanied by changes in the availability of nutrients and elements such as oxygen and iron. As such, nutrients, oxygen, and iron are important determinants of virulence factor synthesis in S. aureus. In addition to influencing virulence factor synthesis, oxygen and iron are critical cofactors in enzymatic and electron transfer reactions; thus, a change in iron or oxygen availability alters the bacterial metabolome. Changes in metabolism create intracellular signals that alter the activity of metabolite-responsive regulators such as CodY, RpiRc, and CcpA. To assess the extent of metabolomic changes associated with oxygen and iron limitation, S. aureus cells were cultivated in iron-limited medium and/or with decreasing aeration, and the metabolomes were examined by nuclear magnetic resonance (NMR) spectroscopy. As expected, oxygen and iron limitation dramatically decreased tricarboxylic acid (TCA) cycle activity, creating a metabolic block and significantly altering the metabolome. These changes were most prominent during post-exponential-phase growth, when TCA cycle activity was maximal. Importantly, many of the effects of iron limitation were obscured by aeration limitation. Aeration limitation not only obscured the metabolic effects of iron limitation but also overrode the transcription of iron-regulated genes. Finally, in contrast to previous speculation, we confirmed that acidification of the culture medium occurs independent of the availability of iron. PMID:24706736

Effects of Aeration of Sawdust Cultivation Bags on Hyphal Growth of Lentinula edodes

PubMed Central

Lee, Hwa-Yong; Ham, Eun-Ju; Yoo, Young-Jin; Kim, Eui-Sung; Shim, Kyu-Kwang; Kim, Myung-Kon

2012-01-01

The effects of aeration through lid filters on the hyphal growth of Lentinula edodes (oak mushroom) in sawdust cultivation bags were investigated. The aeration treatment levels were traditional 27 mm hole cotton plugs, cotton balls and combinations of seven hole sizes × two hole positions (up and under) in the lids covering plastic bags containing 1.4 kg sawdust medium at 63% moisture that had been autoclaved for one hour and inoculated with sawdust spawn of L. edodes strain 921. Aeration treatment effects were measured based on the CO2 concentration at the 15th wk, as well as the hyphal growth rate and degree of weight loss of bags every 14 days for 15 wk. In bags with traditional cotton plugs, the CO2 concentration was 3.8 ± 1.3%, daily mean hyphal growth was 2.3 ± 0.6 mm and daily mean weight loss was 0.84 ± 0.26 g. In the bags with 15 mm diameter holes, the CO2 concentration was 6.0 ± 1.6%, daily hyphal growth was 2.8 ± 0.2 mm and daily weight loss was 0.86 ± 0.4 g. The bags with 15 mm holes had a higher CO2 concentration and lower water loss than bags with other hole sizes, but the hyphal growth was not significantly different from that of other bags. The weight loss of bags increased proportionally relative to the lid hole sizes. Taken together, these results indicate that traditional cotton plugs are economically efficient, but 15 mm hole lids are the most efficient at maintaining hyphal growth and controlling water loss while allowing CO2 emissions. PMID:23115508

Induction of microcin B17 formation in Escherichia coli ZK650 by limitation of oxygen and glucose is independent of glucose consumption rate

NASA Technical Reports Server (NTRS)

Gao, Q.; Fang, A.; Demain, A. L.

2001-01-01

We examined the consumption of glucose from the media in which Escherichia coli ZK650 was grown. This organism, which produces the polypeptide antibiotic microcin B17 best under conditions of limiting supplies of glucose and air, was grown with a low level of glucose (0.5 mg/ml) as well as a high level (5.0 mg/ml) under both high and low aeration. Glucose consumption rates were virtually identical under both high and low aeration. Thus, glucose consumption rate is not a regulating factor in microcin B17 formation.

Solid-state Fermentation of Xylanase from Penicillium canescens 10-10c in a Multi-layer-packed Bed Reactor

NASA Astrophysics Data System (ADS)

Assamoi, Antoine A.; Destain, Jacqueline; Delvigne, Frank; Lognay, Georges; Thonart, Philippe

Xylanase is produced by Penicillium canescens 10-10c from soya oil cake in static conditions using solid-state fermentation. The impact of several parameters such as the nature and the size of inoculum, bed-loading, and aeration is evaluated during the fermentation process. Mycelial inoculum gives more production than conidial inoculum. Increasing the quantity of inoculum enhances slightly xylanase production. Forced aeration induces more sporulation of strain and reduces xylanase production. However, forced moistened air improves the production compared to production obtained with forced dry air. In addition, increasing bed-loading reduces the specific xylanase production likely due to the incapacity of the Penicillium strain to grow deeply in the fermented soya oil cake mass. Thus, the best cultivation conditions involve mycelial inoculum form, a bed loading of 1-cm height and passive aeration. The maximum xylanase activity is obtained after 7 days of fermentation and attains 10,200 U/g of soya oil cake. These levels are higher than those presented in the literature and, therefore, show all the potentialities of this stock and this technique for the production of xylanase.

A novel aerated surface flow constructed wetland using exhaust gas from biological wastewater treatment: Performance and mechanisms.

PubMed

Zhang, Xinwen; Hu, Zhen; Zhang, Jian; Fan, Jinlin; Ngo, Huu Hao; Guo, Wenshan; Zeng, Chujun; Wu, Yiwen; Wang, Siyuan

2018-02-01

In this study, a novel aerated surface flow constructed wetland (SFCW) using exhaust gas from biological wastewater treatment was investigated. Compared with un-aerated SFCW, the introduction of exhaust gas into SFCW significantly improved NH 4 + -N, TN and COD removal efficiencies by 68.30 ± 2.06%, 24.92 ± 1.13% and 73.92 ± 2.36%, respectively. The pollutants removal mechanism was related to the microbial abundance and the highest microbial abundance was observed in the SFCW with exhaust gas because of the introduction of exhaust gas from sequencing batch reactor (SBR), and thereby optimizing nitrogen transformation processes. Moreover, SFCW would significantly mitigate the risk of exhaust gas pollution. SFCW removed 20.00 ± 1.23%, 34.78 ± 1.39%, and 59.50 ± 2.33% of H 2 S, NH 3 and N 2 O in the exhaust gas, respectively. And 31.32 ± 2.23% and 32.02 ± 2.86% of bacterial and fungal aerosols in exhaust gas were also removed through passing SFCW, respectively. Copyright © 2017. Published by Elsevier Ltd.

Air bubbles induce a critical continuous stress to prevent marine biofouling accumulation

NASA Astrophysics Data System (ADS)

Belden, Jesse; Menesses, Mark; Dickenson, Natasha; Bird, James

2017-11-01

Significant shear stresses are needed to remove established hard fouling organisms from a ship hull. Given that there is a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. One approach to mitigate marine biofouling is to continuously introduce a curtain of air bubbles under a submerged surface; it is believed that this aeration exploits the small stresses induced by rising bubbles to continuously prevent accumulation. Although curtains of rising bubbles have successfully prevented biofouling accumulation, it is unclear if a single stream of bubbles could maintain a clean surface. In this talk, we show that single bubble stream aeration can prevent biofouling accumulation in regions for which the average wall stress exceeds approximately 0.01 Pa. This value is arrived at by comparing observations of biofouling growth and prevention from field studies with laboratory measurements that probe the associated flow fields. We also relate the spatial and temporal characteristics of the flow to the size and frequency of the rising bubbles, which informs the basic operating conditions required for aeration to continuously prevent biofouling accumulation.

Concurrent Phosphorus Recovery and Energy Generation in Mediator-Less Dual Chamber Microbial Fuel Cells: Mechanisms and Influencing Factors

PubMed Central

Almatouq, Abdullah; Babatunde, Akintunde O.

2016-01-01

This study investigated the mechanism and key factors influencing concurrent phosphorus (P) recovery and energy generation in microbial fuel cells (MFC) during wastewater treatment. Using a mediator-less dual chamber microbial fuel cell operated for 120 days; P was shown to precipitate as struvite when ammonium and magnesium chloride solutions were added to the cathode chamber. Monitoring data for chemical oxygen demand (COD), pH, oxidation reduction potential (ORP) and aeration flow rate showed that a maximum 38% P recovery was achieved; and this corresponds to 1.5 g/L, pH > 8, −550 ± 10 mV and 50 mL/min respectively, for COD, pHcathode, ORP and cathode aeration flow rate. More importantly, COD and aeration flow rate were shown to be the key influencing factors for the P recovery and energy generation. Results further show that the maximum P recovery corresponds to 72 mW/m2 power density. However, the energy generated at maximum P recovery was not the optimum; this shows that whilst P recovery and energy generation can be concurrently achieved in a microbial fuel cell, neither can be at the optimal value. PMID:27043584

Optimization of Wastewater of Batik Buaran Pekalongan by Using Photocatalytic Membrane Bioreactor

NASA Astrophysics Data System (ADS)

Arifan, Fahmi; Nugraheni, FS; Lianandaya, Niken Elsa

2018-02-01

The purpose of this study is to determine the final COD concentration reduction by changing COD and MLSS concentration on the performance of submerged membrane bioreactor (MBRs) as a waste treatment of Batik in Buaran Pekalongan. The method is covers the process of seeding, the acclimatization process and the main process. Description of the process that we take an active mud from IPLT Buaran Pekalongan, then we analyze the sludge MLSS, MLVSS, COD, BOD, and TSS. After that we enter the active sludge in the bath nursery that has been given aerator (a tool for aeration) and made provision in the form of NPK nutrients and glucose at a ratio of 1:10. Activated sludge from the acclimatization process is inserted into the MBRs (membrane bioreactor submerged) that is equipped with an aerator. Then prepare influent(waste to be lowered concentration of COD). How, liquid waste of Batik Pekalongan Buaran COD diluted concentration of 10,000 mg / l and 15,000 mg / l, and then inserted in influent tub. After that liquid waste of Batik Buaran Pekalongan influent flowed into Photocatalytic Membrane Bioreactor, of MPB effluent flowed into the tub (result).

Simultaneous microalgal biomass production and CO2 fixation by cultivating Chlorella sp. GD with aquaculture wastewater and boiler flue gas.

PubMed

Kuo, Chiu-Mei; Jian, Jhong-Fu; Lin, Tsung-Hsien; Chang, Yu-Bin; Wan, Xin-Hua; Lai, Jinn-Tsyy; Chang, Jo-Shu; Lin, Chih-Sheng

2016-12-01

A microalgal strain, Chlorella sp. GD, cultivated in aquaculture wastewater (AW) aerated with boiler flue gas, was investigated. When AW from a grouper fish farm was supplemented with additional nutrients, the microalgal biomass productivity after 7days of culture was 0.794gL -1 d -1 . CO 2 fixation efficiencies of the microalgal strains aerated with 0.05, 0.1, 0.2, and 0.3vvm of boiler flue gas (containing approximately 8% CO 2 ) were 53, 51, 38, and 30%, respectively. When the microalgal strain was cultured with boiler flue gas in nutrient-added AW, biomass productivity increased to 0.892gL -1 d -1 . In semi-continuous cultures, average biomass productivities of the microalgal strain in 2-day, 3-day, and 4-day replacement cultures were 1.296, 0.985, and 0.944gL -1 d -1 , respectively. These results demonstrate the potential of using Chlorella sp. GD cultivations in AW aerated with boiler flue gas for reusing water resources, reducing CO 2 emission, and producing microalgal biomass. Copyright © 2016 Elsevier Ltd. All rights reserved.

Arsenic accumulation and speciation in rice are affected by root aeration and variation of genotypes.

PubMed

Wu, Chuan; Ye, Zhihong; Shu, Wensheng; Zhu, Yongguan; Wong, Minghung

2011-05-01

Root aeration, arsenic (As) accumulation, and speciation in rice of 20 different genotypes with regular irrigation of water containing 0.4 mg As l(-1) were investigated. Different genotypes had different root anatomy demonstrated by entire root porosity (ranging from 12.43% to 33.21%), which was significantly correlated with radial oxygen loss (ROL) (R=0.64, P<0.01). Arsenic accumulation differed between genotypes, but there were no significant differences between Indica and Japonica subspecies, as well as paddy and upland rice. Total ROL from entire roots was correlated with metal tolerance (expressed as percentage mean of control straw biomass, R=0.69, P<0.01) among the 20 genotypes; total As concentration (R=-0.67, P<0.01) and inorganic As concentration (R=-0.47, P<0.05) in rice grains of different genotypes were negatively correlated with ROL. There were also significant genotype effects in percentage inorganic As (F=15.8, P<0.001) and percentage cacodylic acid (F=22.1, P<0.001), respectively. Root aeration of different genotypes and variation of genotypes on As accumulation and speciation would be useful for selecting genotypes to grow in areas contaminated by As.

Concurrent Phosphorus Recovery and Energy Generation in Mediator-Less Dual Chamber Microbial Fuel Cells: Mechanisms and Influencing Factors.

PubMed

Almatouq, Abdullah; Babatunde, Akintunde O

2016-03-29

This study investigated the mechanism and key factors influencing concurrent phosphorus (P) recovery and energy generation in microbial fuel cells (MFC) during wastewater treatment. Using a mediator-less dual chamber microbial fuel cell operated for 120 days; P was shown to precipitate as struvite when ammonium and magnesium chloride solutions were added to the cathode chamber. Monitoring data for chemical oxygen demand (COD), pH, oxidation reduction potential (ORP) and aeration flow rate showed that a maximum 38% P recovery was achieved; and this corresponds to 1.5 g/L, pH > 8, -550 ± 10 mV and 50 mL/min respectively, for COD, pH(cathode), ORP and cathode aeration flow rate. More importantly, COD and aeration flow rate were shown to be the key influencing factors for the P recovery and energy generation. Results further show that the maximum P recovery corresponds to 72 mW/m² power density. However, the energy generated at maximum P recovery was not the optimum; this shows that whilst P recovery and energy generation can be concurrently achieved in a microbial fuel cell, neither can be at the optimal value.

Effect of matured compost as an inoculating agent on odour removal and maturation of vegetable and fruit waste compost.

PubMed

Chen, Chih-Yu; Kuo, Jong-Tar; Chung, Ying-Chien

2013-01-01

The use of matured compost as an inoculation agent to improve the composting of vegetable and fruit wastes in a laboratory-scale composter was evaluated, and the commercial feasibility of this approach in a pilot-scale (1.8 x 10(4) L) composter was subsequently confirmed. The effect of aeration rate on the physico-chemical and biological properties of compost was also studied. Aeration rate affected the fermentation temperature, moisture content, pH, O2 consumption rate, CO2 production rate and the formation of odour. The optimal aeration rate was 2.5 L air/kg dry solid/min. The CO2 production rate approached the theoretical value during composting and was linearly dependent on temperature, indicating that the compost system had good operating characteristics. The inoculation of cellulolytic bacteria and deodorizing bacteria to compost in the pilot-scale composter led to an 18.2% volatile solids loss and a 64.3% volume reduction ratio in 52 h; only 1.5 ppm(v) odour was detected. This is the first study to focus on both operating performance and odour removal in a pilot-scale composter.

[The effect of pemolin on the mitotic activity of Vicia faba L (author's transl)].

PubMed

Brabec, F; Röper, W

1976-02-01

The effect of diverse concentrations of 5-phenyl-2-imino-4-oxazolidone (PIO, pemolin, Tradon) on the mitotic activity in lateral roots of Vicia faba L. was studied by aerated and non-aerated hydrocultivation with and without mineral nutrition, respectively. With optimal conditions (aerated nutrient solution) weak PIO-concentrations, most significantly 10(-6) g/ml, effected a marked increase of the mitotic index. Contrarily, strong PIO-concentrations (10(-4) and 3 X 10(-4) g/ml = saturated solution) significantly decreased the mitotic index though simultaneously preserving the mitotic activity in long-term experiments, when on account of nutrient deficiency it had already collapsed in weak PIO-concentrations and the controls. The activating effect of weak PIO-concentrations compared with the controls is more significant in stress situations (nutrient deficiency, O2-deficiency) than under optimal conditions. Furthermore a slight acceleration of mid-mitotic phases (metaphase--anaphase) recognized by a marked decrease in percentage of these phases, can be stated with weak PIO-concentrations, again particularly so with 10(-6) g/ml. In total, dependent on concentration, pemolin presumably may either activate or suppress cell metabolism and particularly the mitotic cycle. The exact site of action of the substance is still unknown.

Scale translation from shaken to diffused bubble aerated systems for lycopene production by Blakeslea trispora under stimulated conditions.

PubMed

Mantzouridou, Fani Th; Naziri, Eleni

2017-03-01

This study deals with the scale up of Blakeslea trispora culture from the successful surface-aerated shake flasks to dispersed-bubble aerated column reactor for lycopene production in the presence of lycopene cyclase inhibitor 2-methyl imidazole. Controlling the initial volumetric oxygen mass transfer coefficient (k L a) via airflow rate contributes to increasing cell mass and lycopene accumulation. Inhibitor effectiveness seems to decrease in conditions of high cell mass. Optimization of crude soybean oil (CSO), airflow rate, and 2-methyl imidazole was arranged according to central composite statistical design. The optimized levels of factors were 110.5 g/L, 2.3 vvm, and 29.5 mg/L, respectively. At this optimum setting, maximum lycopene yield (256 mg/L) was comparable or even higher to those reported in shake flasks and stirred tank reactor. 2-Methyl imidazole use at levels significantly lower than those reported for other inhibitors in the literature was successful in terms of process selectivity. CSO provides economic benefits to the process through its ability to stimulate lycopene synthesis, as an inexpensive carbon source and oxygen vector at the same time.

GHG emissions during the high-rate production of compost using standard and advanced aeration strategies.

PubMed

Puyuelo, B; Gea, T; Sánchez, A

2014-08-01

In this study, we have evaluated different strategies for the optimization of the aeration during the active thermophilic stage of the composting process of source-selected Organic Fraction of Municipal Solid Waste (or biowaste) using reactors at bench scale (50L). These strategies include: typical cyclic aeration, oxygen feedback controller and a new self-developed controller based on the on-line maximization of the oxygen uptake rate (OUR) during the process. Results highlight differences found in the emission of most representative greenhouse gases (GHG) emitted from composting (methane and nitrous oxide) as well as in gases typically related to composting odor problems (ammonia as typical example). Specifically, the cyclic controller presents emissions that can double that of OUR controller, whereas oxygen feedback controller shows a better performance with respect to the cyclic controller. A new parameter, the respiration index efficiency, is presented to quantitatively evaluate the GHG emissions and, in consequence, the main negative environmental impact of the composting process. Other aspects such as the stability of the compost produced and the consumption of resources are also evaluated for each controller. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of culture medium, host strain and oxygen transfer on recombinant Fab antibody fragment yield and leakage to medium in shaken E. coli cultures.

PubMed

Ukkonen, Kaisa; Veijola, Johanna; Vasala, Antti; Neubauer, Peter

2013-07-29

Fab antibody fragments in E. coli are usually directed to the oxidizing periplasmic space for correct folding. From periplasm Fab fragments may further leak into extracellular medium. Information on the cultivation parameters affecting this leakage is scarce, and the unpredictable nature of Fab leakage is problematic regarding consistent product recovery. To elucidate the effects of cultivation conditions, we investigated Fab expression and accumulation into either periplasm or medium in E. coli K-12 and E. coli BL21 when grown in different types of media and under different aeration conditions. Small-scale Fab expression demonstrated significant differences in yield and ratio of periplasmic to extracellular Fab between different culture media and host strains. Expression in a medium with fed-batch-like glucose feeding provided highest total and extracellular yields in both strains. Unexpectedly, cultivation in baffled shake flasks at 150 rpm shaking speed resulted in higher yield and accumulation of Fabs into culture medium as compared to cultivation at 250 rpm. In the fed-batch medium, extracellular fraction in E. coli K-12 increased from 2-17% of total Fab at 250 rpm up to 75% at 150 rpm. This was partly due to increased lysis, but also leakage from intact cells increased at the lower shaking speed. Total Fab yield in E. coli BL21 in glycerol-based autoinduction medium was 5 to 9-fold higher at the lower shaking speed, and the extracellular fraction increased from ≤ 10% to 20-90%. The effect of aeration on Fab localization was reproduced in multiwell plate by variation of culture volume. Yield and leakage of Fab fragments are dependent on expression strain, culture medium, aeration rate, and the combination of these parameters. Maximum productivity in fed-batch-like conditions and in autoinduction medium is achieved under sufficiently oxygen-limited conditions, and lower aeration also promotes increased Fab accumulation into extracellular medium. These findings have practical implications for screening applications and small-scale Fab production, and highlight the importance of maintaining consistent aeration conditions during scale-up to avoid changes in product yield and localization. On the other hand, the dependency of Fab leakage on cultivation conditions provides a practical way to manipulate Fab localization.

Effect of culture medium, host strain and oxygen transfer on recombinant Fab antibody fragment yield and leakage to medium in shaken E. coli cultures

PubMed Central

2013-01-01

Background Fab antibody fragments in E. coli are usually directed to the oxidizing periplasmic space for correct folding. From periplasm Fab fragments may further leak into extracellular medium. Information on the cultivation parameters affecting this leakage is scarce, and the unpredictable nature of Fab leakage is problematic regarding consistent product recovery. To elucidate the effects of cultivation conditions, we investigated Fab expression and accumulation into either periplasm or medium in E. coli K-12 and E. coli BL21 when grown in different types of media and under different aeration conditions. Results Small-scale Fab expression demonstrated significant differences in yield and ratio of periplasmic to extracellular Fab between different culture media and host strains. Expression in a medium with fed-batch-like glucose feeding provided highest total and extracellular yields in both strains. Unexpectedly, cultivation in baffled shake flasks at 150 rpm shaking speed resulted in higher yield and accumulation of Fabs into culture medium as compared to cultivation at 250 rpm. In the fed-batch medium, extracellular fraction in E. coli K-12 increased from 2-17% of total Fab at 250 rpm up to 75% at 150 rpm. This was partly due to increased lysis, but also leakage from intact cells increased at the lower shaking speed. Total Fab yield in E. coli BL21 in glycerol-based autoinduction medium was 5 to 9-fold higher at the lower shaking speed, and the extracellular fraction increased from ≤ 10% to 20-90%. The effect of aeration on Fab localization was reproduced in multiwell plate by variation of culture volume. Conclusions Yield and leakage of Fab fragments are dependent on expression strain, culture medium, aeration rate, and the combination of these parameters. Maximum productivity in fed-batch-like conditions and in autoinduction medium is achieved under sufficiently oxygen-limited conditions, and lower aeration also promotes increased Fab accumulation into extracellular medium. These findings have practical implications for screening applications and small-scale Fab production, and highlight the importance of maintaining consistent aeration conditions during scale-up to avoid changes in product yield and localization. On the other hand, the dependency of Fab leakage on cultivation conditions provides a practical way to manipulate Fab localization. PMID:23895637

Fe hydroxyphosphate precipitation and Fe(II) oxidation kinetics upon aeration of Fe(II) and phosphate-containing synthetic and natural solutions

NASA Astrophysics Data System (ADS)

van der Grift, B.; Behrends, T.; Osté, L. A.; Schot, P. P.; Wassen, M. J.; Griffioen, J.

2016-08-01

Exfiltration of anoxic Fe-rich groundwater into surface water and the concomitant oxidative precipitation of Fe are important processes controlling the transport of phosphate (PO4) from agricultural areas to aquatic systems. Here, we explored the relationship between solution composition, reaction kinetics, and the characteristics of the produced Fe hydroxyphosphate precipitates in a series of aeration experiments with anoxic synthetic water and natural groundwater. A pH stat device was used to maintain constant pH and to record the H+ production during Fe(II) oxidation in the aeration experiments in which the initial aqueous P/Fe ratios ((P/Fe)ini), oxygen concentration and pH were varied. In general, Fe(II) oxidation proceeded slower in the presence of PO4 but the decrease of the PO4 concentration during Fe(II) oxidation due to the formation of Fe hydroxyphosphates caused additional deceleration of the reaction rate. The progress of the reaction could be described using a pseudo-second-order rate law with first-order dependencies on PO4 and Fe(II) concentrations. After PO4 depletion, the Fe(II) oxidation rates increased again and the kinetics followed a pseudo-first-order rate law. The first-order rate constants after PO4 depletion, however, were lower compared to the Fe(II) oxidation in a PO4-free solution. Hence, the initially formed Fe hydroxyphosphates also affect the kinetics of continuing Fe(II) oxidation after PO4 depletion. Presence of aqueous PO4 during oxidation of Fe(II) led to the formation of Fe hydroxyphosphates. The P/Fe ratios of the precipitates ((P/Fe)ppt) and the recorded ratio of H+ production over decrease in dissolved Fe(II) did not change detectably throughout the reaction despite a changing P/Fe ratio in the solution. When (P/Fe)ini was 0.9, precipitates with a (P/Fe)ppt ratio of about 0.6 were formed. In experiments with (P/Fe)ini ratios below 0.6, the (P/Fe)ppt decreased with decreasing (P/Fe)ini and pH value. Aeration experiments with natural groundwater showed no principal differences in Fe(II) oxidation kinetics and in PO4 immobilisation dynamics compared with synthetic solutions with corresponding P/Fe ratio, pH and oxygen pressure. However, aeration of groundwater with relative high DOC concentrations and a low salinity lead to P-rich Fe colloids that were colloidally stable. The formation of a Fe hydroxyphosphate phase with a molar P/Fe ratio of 0.6 can be used for predictive modelling of PO4 immobilisation upon aeration of pH-neutral natural groundwater with an (P/Fe)ini ratio up to 1.5. These findings provide a solid basis for further studies on transport and bioavailability of phosphorus in streams, ditches and channels that receive anoxic Fe-rich groundwater.

Monitoring, field experiments, and geochemical modeling of Fe(II) oxidation kinetics in a stream dominated by net-alkaline coal-mine drainage, Pennsylvania, USA

USGS Publications Warehouse

Cravotta, Charles A.

2015-01-01

Watershed-scale monitoring, field aeration experiments, and geochemical equilibrium and kinetic modeling were conducted to evaluate interdependent changes in pH, dissolved CO2, O2, and Fe(II) concentrations that typically take place downstream of net-alkaline, circumneutral coal-mine drainage (CMD) outfalls and during aerobic treatment of such CMD. The kinetic modeling approach, using PHREEQC, accurately simulates observed variations in pH, Fe(II) oxidation, alkalinity consumption, and associated dissolved gas concentrations during transport downstream of the CMD outfalls (natural attenuation) and during 6-h batch aeration tests on the CMD using bubble diffusers (enhanced attenuation). The batch aeration experiments demonstrated that aeration promoted CO2 outgassing, thereby increasing pH and the rate of Fe(II) oxidation. The rate of Fe(II) oxidation was accurately estimated by the abiotic homogeneous oxidation rate law −d[Fe(II)]/dt = k1·[O2]·[H+]−2·[Fe(II)] that indicates an increase in pH by 1 unit at pH 5–8 and at constant dissolved O2 (DO) concentration results in a 100-fold increase in the rate of Fe(II) oxidation. Adjusting for sample temperature, a narrow range of values for the apparent homogeneous Fe(II) oxidation rate constant (k1′) of 0.5–1.7 times the reference value of k1 = 3 × 10−12 mol/L/min (for pH 5–8 and 20 °C), reported by Stumm and Morgan (1996), was indicated by the calibrated models for the 5-km stream reach below the CMD outfalls and the aerated CMD. The rates of CO2 outgassing and O2ingassing in the model were estimated with first-order asymptotic functions, whereby the driving force is the gradient of the dissolved gas concentration relative to equilibrium with the ambient atmosphere. Although the progressive increase in DO concentration to saturation could be accurately modeled as a kinetic function for the conditions evaluated, the simulation of DO as an instantaneous equilibrium process did not affect the model results for Fe(II) or pH. In contrast, the model results for pH and Fe(II) were sensitive to the CO2 mass transfer rate constant (kL,CO2a). The value of kL,CO2a estimated for the stream (0.010 min−1) was within the range for the batch aeration experiments (0–0.033 min−1). These results indicate that the abiotic homogeneous Fe(II) oxidation rate law, with adjustments for variations in temperature and CO2 outgassing rate, may be applied to predict changes in aqueous iron and pH for net-alkaline, ferruginous waters within a stream (natural conditions) or a CMD treatment system (engineered conditions).

Oxidation of ammonium sulfite in aqueous solutions using ozone technology

NASA Astrophysics Data System (ADS)

Li, Yue; Shang, Kefeng; Lu, Na; Li, Jie; Wu, Yan

2013-03-01

How to deal with unstable ammonium sulfite, the byproduct of flue gas desulfuration by ammonia absorption methods, has been a difficult problem in recent years. Oxidation of ammonium sulfite in aqueous solutions using ozone produced by a surface discharge system was investigated in the paper. The oxidation efficiency of ammonium sulfite by ozone and traditional air aeration were compared, and the factors including ozone concentration, gas flow rate, initial concentration of ammonium sulfite solution and reaction temperature were discussed. The results show that the oxidation efficiency of ammonium sulfite by ozone technology reached nearly 100% under the optimum conditions, which had a significant increase compared with that by air aeration.

Optimization of macronutrient kinetics for biomass production in Nostoc calcicola

NASA Astrophysics Data System (ADS)

Aiyer, Subramanian Seshadri C.; Akshai, A.; Kumar, B. G. Prakash; Ramachandran, S.

2018-04-01

To assess the feasibility of Allen and Arnon’s (AA) media addition to increase the biomass productivity, (0, 2.5, 5, 7.5 ml of 10x media concentrate - MC) was added to aerated culture every six days, in two separate conditions i.e., single harvest (SH) and continuous harvest (CH) after 15th day. Results show that with addition of 5 ml of MC produced maximum amount of biomass is 1.32 g/L and 2.88 g/L for Sh and CH respectively. These results show that with addition of 5 ml of MC to an aerated culture every six days with continuous biomass harvesting leads to maximum growth of Nostoc calcicola @25°C

Comparative analysis of nitrifying bacteria in full-scale oxidation ditch and aerated nitrification biofilter by using fluorescent in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE).

PubMed

Mertoglu, Bulent; Calli, Baris; Girgin, Emine; Inanc, Bulent; Ozturk, Izzet

2005-01-01

In this study, nitrification performances and composition of nitrifying populations in a full-scale oxidation ditch and a high-rate submerged media nitrification biofilter were comparatively analyzed. In addition to different reactor configurations, effects of differing operational conditions on the nitrification efficiency and bacterial diversity were also explored and evaluated thoroughly. In microbial analysis of sludge samples fluorescent in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) techniques were used complementary to each other. The extended aeration oxidation ditch subjected to the study is operated as a nitrogen and phosphorus removal system consisting of anaerobic, anoxic, and aerobic zones. The high-rate submerged media aerated filter is operated as nitrification step following the conventional activated sludge unit and the nitrified wastewater is discharged to the sea without complete nitrogen removal. In situ hybridization results have indicated that Nitrosomonas-like ammonia oxidizing and Nitrospira-related nitrite oxidizing bacteria were intensively present in vigorous flocs in nitrification biofilter while carbonaceous bacteria belong to beta subclass of Proteobacteria were considerably dominant in oxidation ditch. Low quantities of nitrifiers in oxidation ditch were also confirmed by the dissimilarity in intensive bands between two systems obtained with DGGE analysis.

[Effect of Membrane Wettability on Membrane Fouling and Chemical Durability of SPG Membranes].

PubMed

Zhang, Jing; Xiao, Tai-min; Zhang, Jing; Cao, Li-ya; Du, Ya-wei; Liu, Chun; Zhang, Lei

2015-05-01

Shirasu porous glass (SPG) membranes have been applied for microbubble aeration in aerobic wastewater treatment. In the present study, both hydrophilic and hydrophobic SPG membranes were used in a microbubble-aerated biofilm reactor with online chemical cleaning, and their membrane fouling and chemical durability were determined to be strongly dependent on the membrane wettability. The fouling layer formed on the surface of both membranes was confirmed to be mainly organic fouling, and the hydrophobic membrane showed a relatively stronger resistance to the organic fouling. The severe chemical corrosion of the hydrophilic membrane was observed due to exposure to the alkaline sodium hypochlorite solution used for chemical cleaning, which resulted in significant increases in the median pore diameter and the porosity. On the other hand, the pore structure of the hydrophobic membrane changed slightly when exposed to the alkaline sodium hypochlorite solution, suggesting its strong alkali-resistance due to the non-wetting surface. However, the surface hydrophobic groups of hydrophobic membrane could be oxidized by sodium hypochlorite solution, resulting in more wettable membrane surface. The hydrophobic membrane also showed better performance in the respects of oxygen transfer, contaminant removal and energy-saving. Therefore, the hydrophobic membrane seemed more appropriate to be applied for microbubble aeration in aerobic wastewater treatment process.

The study of solid circulation rate in a compartmented fluidized bed gasifier (CFBG)

NASA Astrophysics Data System (ADS)

Wee, S. K.; Pok, Y. W.; Law, M. C.; Lee, V. C. C.

2016-06-01

Biomass waste has been abundantly available in Malaysia since the booming of palm oil industry. In order to tackle this issue, gasification is seen a promising technology to convert waste into energy. In view of the heat requirement for endothermic gasification reaction as well as the complex design and operation of multiple fluidized beds, compartmented fluidized bed gasifier (CFBG) with the combustor and the gasifier as separate compartments is proposed. As such, solid circulation rate (SCR) is one of the essential parameters for steady gasification and combustion to be realized in their respective compartments. Experimental and numerical studies (CFD) on the effect of static bed height, main bed aeration, riser aeration and v-valve aeration on SCR have been conducted in a cold- flow CFBG model with only river sand as the fluidizing medium. At lower operating range, the numerical simulations under-predict the SCR as compared to that of the experimental results. Also, it predicts slightly different trends over the range. On the other hand, at higher operating range, the numerical simulations are able to capture those trends as observed in the experimental results at the lower operating range. Overall, the numerical results compare reasonably well with that of the experimental works.

Mechanisms for naphthalene removal during electrolytic aeration.

PubMed

Goel, Ramesh K; Flora, Joseph R V; Ferry, John

2003-02-01

Batch tests were performed to investigate chemical and physical processes that may result during electrolytic aeration of a contaminated aquifer using naphthalene as a model contaminant. Naphthalene degradation of 58-66% took place electrolytically and occurred at the same rates at a pH of 4 and 7. 1,4-naphthoquinone was identified as a product of the electrolysis. Stripping due to gases produced at the electrodes did not result in any naphthalene loss. Hydrogen peroxide (which may be produced at the cathode) did not have any effect on naphthalene, but the addition of ferrous iron (which may be present in aquifers) resulted in 67-99% disappearance of naphthalene. Chlorine (which may be produced from the anodic oxidation of chloride) can effectively degrade naphthalene at pH of 4, but not at a pH of 7. Mono-, di- and poly chloronaphthalenes were identified as oxidation products. Ferric iron coagulation (due to the oxidation of ferrous iron) did not significantly contribute to naphthalene loss. Overall, electrolytic oxidation and chemical oxidation due to the electrolytic by-products formed are significant abiotic processes that could occur and should be accounted for if bioremediation of PAH-contaminated sites via electrolytic aeration is considered. Possible undesirable products such as chlorinated compounds may be formed when significant amounts of chlorides are present.

Hydrogen peroxide-enhanced iron-mediated aeration for the treatment of mature landfill leachate.

PubMed

Deng, Yang; Englehardt, James D

2008-05-01

Municipal landfill leachate is being disallowed for biological treatment by some sewer authorities due to its recalcitrance and corrosiveness, and therefore physicochemical treatment may be needed. In this paper, hydrogen peroxide-enhanced iron (Fe(0))-mediated aeration (IMA) was studied as an alternative for the treatment of mature landfill leachate. Bench-scale Taguchi array screening tests and full factorial tests were conducted. Iron grade, initial pH, H(2)O(2) addition rate, and aeration rate significantly influenced both overall chemical oxygen demand (COD) removal and iron consumption. In the enhanced IMA-treated leachate at an initial pH of 8.2, COD was reduced by 50% due to oxidation and coagulation, a level almost equivalent to those obtained by Fenton treatment. Meanwhile, the 5-day biochemical oxygen demand (BOD(5))/COD ratio was increased from 0.02 to 0.17. In particular, the effect of initial pH became minor at H(2)O(2) addition rate greater than the theoretical demand for complete oxidation of organics by H(2)O(2). In addition, 83% of 300 mg/L ammonia nitrogen and 38% of 8.30 mS/cm electrical conductivity were removed when the initial pH was not adjusted. Based on these results, the process appears suitable for treatment of mature leachate.

Continuous Dissolved Oxygen Measurements and Modelling Metabolism in Peatland Streams

PubMed Central

Dick, Jonathan J.; Soulsby, Chris; Birkel, Christian; Malcolm, Iain; Tetzlaff, Doerthe

2016-01-01

Stream water dissolved oxygen was monitored in a 3.2km2 moorland headwater catchment in the Scottish Highlands. The stream consists of three 1st order headwaters and a 2nd order main stem. The stream network is fringed by peat soils with no riparian trees, though dwarf shrubs provide shading in the lower catchment. Dissolved oxygen (DO) is regulated by the balance between atmospheric re-aeration and the metabolic processes of photosynthesis and respiration. DO was continuously measured for >1 year and the data used to calibrate a mass balance model, to estimate primary production, respiration and re-aeration for a 1st order site and in the 2nd order main stem. Results showed that the stream was always heterotrophic at both sites. Sites were most heterotrophic in the summer reflecting higher levels of stream metabolism. The 1st order stream appeared more heterotrophic which was consistent with the evident greater biomass of macrophytes in the 2nd order stream, with resulting higher primary productivity. Comparison between respiration, primary production, re-aeration and potential physical controls revealed only weak relationships. However, the most basic model parameters (e.g. the parameter linking light and photosynthesis) controlling ecosystem processes resulted in significant differences between the sites which seem related to the stream channel geometry. PMID:27556278

Influence of aggregate type and chemical admixtures on frost resistance of lightweight mortars

NASA Astrophysics Data System (ADS)

Klimek, Beata; Widomski, Marcin K.; Barnat-Hunek, Danuta

2017-07-01

The aim of studies presented in this paper covered analyses of type of lightweight aggregate as well as aeration and hydrophobic admixtures influence on absorbability and frost resistance of heat-insulating mortars applied in the energy-efficient construction. In the presented research, expanded perlite (EP) and expanded clay aggregate (ceramsite) were used as lightweight aggregates. The measurements of the basic mechanical and physical characteristics of tested mortars were performed, including, inter alia, compressive and flexural tensile strength, density, effective (open) and total porosity, absorbability, thermal conductivity as well as frost resistance after 25 cycles of freezing and thawing. Substitution of some part of sand fraction by the lightweight aggregates, expanded clay aggregate or perlite, resulted in changes in physical properties of the tested mortars. The observed decrease in density (specific weight), coefficient of heat transport and strength parameters were simultaneously accompanied by the increase in absorbability. Researches concerning frost resistance of mortars containing ceramsite and perlite showed the improved frost resistance of mortar utilizing perlite. Most of the tested mortars shoved satisfactory frost resistance, only samples of mortar containing ceramsite and aeration admixture were destroyed. The significant influence of aerating admixture on frost resistance of mortars was determined. Hydrophobic siloxanes addition failed to adequately protect the mortars against frost erosion, regardless the type of applied aggregate.

Assessment of nitrification in groundwater filters for drinking water production by qPCR and activity measurement.

PubMed

de Vet, W W J M; Kleerebezem, R; van der Wielen, P W J J; Rietveld, L C; van Loosdrecht, M C M

2011-07-01

In groundwater treatment for drinking water production, the causes of nitrification problems and the effectiveness of process optimization in rapid sand filters are often not clear. To assess both issues, the performance of a full-scale groundwater filter with nitrification problems and another filter with complete nitrification and pretreatment by subsurface aeration was monitored over nine months. Quantitative real-time polymerase chain reaction (qPCR) targeting the amoA gene of bacteria and archaea and activity measurements of ammonia oxidation were used to regularly evaluate water and filter sand samples. Results demonstrated that subsurface aeration stimulated the growth of ammonia-oxidizing prokaryotes (AOP) in the aquifer. Cell balances, using qPCR counts of AOP for each filter, showed that the inoculated AOP numbers from the aquifer were marginal compared with AOP numbers detected in the filter. Excessive washout of AOP was not observed and did not cause the nitrification problems. Ammonia-oxidizing archaea grew in both filters, but only in low numbers compared to bacteria. The cell-specific nitrification rate in the sand and backwash water samples was high for the subsurface aerated filter, but systematically much lower for the filter with nitrification problems. From this, we conclude that incomplete nitrification was caused by nutrient limitation. Copyright © 2011 Elsevier Ltd. All rights reserved.

Seasonal influence of environmental variables and artificial aeration on Escherichia coli in small urban lakes.

PubMed

Durham, Bart W; Porter, Lucy; Webb, Allie; Thomas, Joshua

2016-12-01

This study investigated patterns of Escherichia coli in urban lakes in Lubbock, Texas. Specific objectives were to (1) document seasonal patterns in abundance of E. coli over a 3-year period, (2) identify environmental factors, including effects of migratory geese and artificial aeration devices that may influence E. coli abundance, and (3) determine if E. coli abundance over time was similar for individual lakes. Water samples were collected monthly for 36 months from six lakes, three of which contained artificial aeration devices (fountains). Regression models were constructed to determine which environmental variables most influence E. coli abundance in summer and winter seasons. Escherichia coli is present in the lakes of Lubbock, Texas year-round and typically exceeds established bacterial thresholds for recreational waters. Models most frequently contained pH and dissolved oxygen as predictor variables and explained from 17.4% to 92.4% of total variation in E. coli. Lakes with fountains had a higher oxygen concentration during summer and contained consistently less E. coli. We conclude that solar irradiation in synergy with pH and dissolved oxygen is the primary control mechanism for E. coli in study lakes, and that fountains help control abundance of fecal bacteria within these systems.

Cost minimization in a full-scale conventional wastewater treatment plant: associated costs of biological energy consumption versus sludge production.

PubMed

Sid, S; Volant, A; Lesage, G; Heran, M

2017-11-01

Energy consumption and sludge production minimization represent rising challenges for wastewater treatment plants (WWTPs). The goal of this study is to investigate how energy is consumed throughout the whole plant and how operating conditions affect this energy demand. A WWTP based on the activated sludge process was selected as a case study. Simulations were performed using a pre-compiled model implemented in GPS-X simulation software. Model validation was carried out by comparing experimental and modeling data of the dynamic behavior of the mixed liquor suspended solids (MLSS) concentration and nitrogen compounds concentration, energy consumption for aeration, mixing and sludge treatment and annual sludge production over a three year exercise. In this plant, the energy required for bioreactor aeration was calculated at approximately 44% of the total energy demand. A cost optimization strategy was applied by varying the MLSS concentrations (from 1 to 8 gTSS/L) while recording energy consumption, sludge production and effluent quality. An increase of MLSS led to an increase of the oxygen requirement for biomass aeration, but it also reduced total sludge production. Results permit identification of a key MLSS concentration allowing identification of the best compromise between levels of treatment required, biological energy demand and sludge production while minimizing the overall costs.

Post-anoxic denitrification via nitrite driven by PHB in feast-famine sequencing batch reactor.

PubMed

Chen, Hong-Bo; Yang, Qi; Li, Xiao-Ming; Wang, Yan; Luo, Kun; Zeng, Guang-Ming

2013-08-01

Recently, it was found that excess phosphorus removal could be induced by aerobic/extended-idle regime. In this study, an anoxic period was introduced after the aeration to realize simultaneous nitrogen and phosphorus removal. The results demonstrated that stable partial nitrification could be achieved by controlling the aeration duration at 2.5h because it could not only obtain a desirable ammonia oxidation to nitrite but also avoid the extensive aeration converting nitrite to nitrate, and moreover, the accumulated poly-3-hydroxybutyrate still remain in a relative sufficient concentration (1.5mmolCg(-1) VSS), which could subsequently served as internal carbon source for post-anoxic denitrification. The nitrite accumulation ratio was observed to have relatively high correlation with biological nutrient removal. Over stages with stable high-level nitrite accumulation, the process achieved desirable and stable nitrogen and phosphorus removal efficiencies averaging 95% and 99% respectively. Fluorescence in situ hybridization analysis showed that the faster growth rate of the ammonia oxidizing bacteria than the nitrite oxidizing bacteria was the main reason for achieving nitrite accumulation. In addition, the secondary phosphorus release was negligible and the process maintained excellent nutrient removal under low influent ammonia nitrogen. Copyright © 2013 Elsevier Ltd. All rights reserved.

Optimization of probiotic and lactic acid production by Lactobacillus plantarum in submerged bioreactor systems.

PubMed

Brinques, Graziela Brusch; do Carmo Peralba, Maria; Ayub, Marco Antônio Záchia

2010-02-01

Biomass and lactic acid production by a Lactobacillus plantarum strain isolated from Serrano cheese, a microorganism traditionally used in foods and recognized as a potent probiotic, was optimized. Optimization procedures were carried out in submerged batch bioreactors using cheese whey as the main carbon source. Sequential experimental Plackett-Burman designs followed by central composite design (CCD) were used to assess the influence of temperature, pH, stirring, aeration rate, and concentrations of lactose, peptone, and yeast extract on biomass and lactic acid production. Results showed that temperature, pH, aeration rate, lactose, and peptone were the most influential variables for biomass formation. Under optimized conditions, the CCD for temperature and aeration rate showed that the model predicted maximal biomass production of 14.30 g l(-1) (dw) of L. plantarum. At the central point of the CCD, a biomass of 10.2 g l(-1) (dw), with conversion rates of 0.10 g of cell g(-1) lactose and 1.08 g lactic acid g(-1) lactose (w/w), was obtained. These results provide useful information about the optimal cultivation conditions for growing L. plantarum in batch bioreactors in order to boost biomass to be used as industrial probiotic and to obtain high yields of conversion of lactose to lactic acid.

Enhancement of Bacillus subtilis Lipopeptide Biosurfactants Production through Optimization of Medium Composition and Adequate Control of Aeration.

PubMed

Ghribi, Dhouha; Ellouze-Chaabouni, Semia

2011-01-01

Interest in biosurfactants has increased considerably in recent years, as they are potentially used in many commercial applications in petroleum, pharmaceuticals, biomedical, and food processing industries. Since improvement of their production was of great importance to reduce the final coast, cultural conditions were analyzed to optimize biosurfactants production from Bacillus subtilis SPB1 strain. A high yield of biosurfactants was obtained from a culture of B. subtilis using carbohydrate substrate as a carbon source; among carbohydrates, glucose enhanced the best surfactin production. The optimum glucose concentration was 40 g/L. Higher amount of biosurfactants was obtained using 5 g/L of urea as organic nitrogen source and applying C/N ratio of 7 with ammonium chloride as inorganic nitrogen source. The highest amount of biosurfactants was recorded with the addition of 2% kerosene. Moreover, it was shown, using an automated full-controlled 2.6 L fermenter, that aeration of the medium, which affected strongly the growth regulated biosurfactants synthesis by the producing cell. So that, low or high aerations lead to a decrease of biosurfactants synthesis yields. It was found that when using dissolved oxygen saturation of the medium at 30%, biosurfactants production reached 4.92 g/L.

The Effects of Storm Runoff on Water Quality and the Coping Strategy of a Deep Canyon-Shaped Source Water Reservoir in China

PubMed Central

Ma, Weixing; Huang, Tinglin; Li, Xuan; Zhou, Zizhen; Li, Yang; Zeng, Kang

2015-01-01

Storm runoff events in the flooding season affect the water quality of reservoirs and increase risks to the water supply, but coping strategies have seldom been reported. The phenomenon of turbid current intrusion resulting in water turbidity and anoxic conditions reappearing after storm runoff, resulting in the deterioration of water quality, was observed in the flooding season in the deep canyon-shaped Heihe Reservoir. The objective of this work was to elucidate the effects of storm runoff on the Heihe Reservoir water quality and find a coping strategy. In this study, an intensive sampling campaign measuring water temperature, dissolved oxygen, turbidity, nutrients, and metals were conducted in the reservoir over a period of two years, and the water-lifting aerators were improved to achieve single aeration and a full layer of mixing and oxygenation functions using different volumes of gas. The operation of the improved water-lifting aerators mixed the reservoir three months ahead of the natural mixing time, and good water quality was maintained during the induced mixing period, thereby extending the good water quality period. The results can provide an effective coping strategy to improve the water quality of a source water reservoir and ensure the safety of drinking water. PMID:26184258

Carbon dioxide stripping in aquaculture -- part II: development of gas transfer models

USGS Publications Warehouse

Colt, John; Watten, Barnaby; Pfeiffer, Tim

2012-01-01

The basic mass transfer equation for gases such as oxygen and carbon dioxide can be derived from integration of the driving force equation. Because of the physical characteristics of the gas transfer processes, slightly different models are used for aerators tested under the non steady-state procedures, than for packed columns, or weirs. It is suggested that the standard condition for carbon dioxide should be 20 °C, 1 atm, CCO2=20 mg/kg, and XCO2=0.000285. The selection of the standard condition for carbon dioxide based on a fixed mole fraction ensures that standardized carbon dioxide transfer rates will be comparable even though the value of C*CO2 in the atmosphere is increasing with time. The computation of mass transfer for carbon dioxide is complicated by the impact of water depth and gas phase enrichment on the saturation concentration within the unit, although the importance of either factor depends strongly on the specific type of aerator. For some types of aerators, the most accurate gas phase model remains to be determined for carbon dioxide. The assumption that carbon dioxide can be treated as a non-reactive gas in packed columns may apply for cold acidic waters but not for warm alkaline waters.

Bacterial community analysis of anoxic/aeration (A/O) system in a combined process for gibberellin wastewater treatment

PubMed Central

Ouyang, Erming; Lu, Yao; Ouyang, Jiating; Wang, Lele; Wang, Xiaohui

2017-01-01

Gibberellin wastewater cannot be directly discharged without treatment due to its high concentrations of sulfate and organic compounds and strong acidity. Therefore, multi-stage anaerobic bioreactor + micro-aerobic+ anoxic/aeration (A/O) + biological contact oxidation combined processes are used to treat gibberellin wastewater. However, knowledge of the treatment effects of the A/O process and bacterial community structure in the aeration tank reactors of such systems is sparse. Therefore, this study was conducted to investigate the treatment effects and operation of the A/O process on gibberellin wastewater, as well as changes in the bacterial community structure of activated sludge in the aeration tank during treatment. Moreover, removal was examined based on evaluation of effluent after A/O treatment. Although influent chemical oxygen demand (COD), NH3-N and total phosphorus (TP) fluctuated, effluent COD, NH3-N and TP remained stable. Moreover, average COD, NH3-N and TP removal efficiency were 68.41%, 93.67% and 45.82%, respectively, during the A/O process. At the phylum level, Proteobacteria was the dominant phylum in all samples, followed by Chloroflexi, Bacteroidetes and Actinobacteria. Proteobacteria played an important role in the removal of organic matter. Chloroflexi was found to be responsible for the degradation of carbohydrates and Bacteroidetes also had been found to be responsible for the degradation of complex organic matters. Actinobacteria are able to degrade a variety of environmental chemicals. Additionally, Anaerolineaceae_uncultured was the major genus in samples collected on May 25, 2015, while Novosphingobium and Nitrospira were dominant in most samples. Nitrosomonas are regarded as the dominant ammonia-oxidizing bacteria, while Nitrospira are the main nitrite-oxidizing bacteria. Bacterial community structure varied considerably with time, and a partial Mantel test showed a highly significant positive correlation between bacterial community structure and DO. The bacterial community structure was also positively correlated with temperature and SO42-. PMID:29053751

Study on the quality and stability of compost through a Demo Compost Plant.

PubMed

Hasan, K M M; Sarkar, G; Alamgir, M; Bari, Q H; Haedrich, G

2012-11-01

This study is concerned with the performance of a Demo Compost Plant for the development of acceptable composting technology in Bangladesh. The Demo Compost Plant was setup at the adjacent area of an existing compost plant located at Khulna city in Bangladesh. Four different composting technologies were considered, where Municipal Solid Waste (MSW) were used as a raw material for composting, collected from the adjacent areas of the plant. Initially the whole composting system was conducted through two experimental setups. In the 1st setup three different types of aerators (horizontal and vertical passively aerator and forced aerator) were selected. For a necessary observation four piles, using only MSW as the input materials in the first three compost pile, the fourth one was the existing Samadhan's compost pile. Based on the analysis of the experimental findings, the horizontal passively aerated composting technique is suitable for Bangladesh as it had better performance for reducing composting period than that of the others. It was being observed from the quality parameters of compost in the both 1st and 2nd setup that as the waste directly come from kitchen, degradation rate of waste shows a positive result for reducing this waste and there is no possibility of toxic contamination, when it would be used as a soil conditioner. Though there is no significant improvement in the quality of the final product in the 2nd setup as comparing with the 1st setup but it fulfills one of the main objectives of this study is to reduce the whole composting period as well as immediate management of the increasing amount of waste and reducing load on landfill. Selfheating tests reveal that degree of stability of compost with respect to maturation period was remained in the acceptable level, which was further accelerated due to the use of organic additives. Copyright © 2012 Elsevier Ltd. All rights reserved.

Validation study of an interpolation method for calculating whole lung volumes and masses from reduced numbers of CT-images in ponies.

PubMed

Reich, H; Moens, Y; Braun, C; Kneissl, S; Noreikat, K; Reske, A

2014-12-01

Quantitative computer tomographic analysis (qCTA) is an accurate but time intensive method used to quantify volume, mass and aeration of the lungs. The aim of this study was to validate a time efficient interpolation technique for application of qCTA in ponies. Forty-one thoracic computer tomographic (CT) scans obtained from eight anaesthetised ponies positioned in dorsal recumbency were included. Total lung volume and mass and their distribution into four compartments (non-aerated, poorly aerated, normally aerated and hyperaerated; defined based on the attenuation in Hounsfield Units) were determined for the entire lung from all 5 mm thick CT-images, 59 (55-66) per animal. An interpolation technique validated for use in humans was then applied to calculate qCTA results for lung volumes and masses from only 10, 12, and 14 selected CT-images per scan. The time required for both procedures was recorded. Results were compared statistically using the Bland-Altman approach. The bias ± 2 SD for total lung volume calculated from interpolation of 10, 12, and 14 CT-images was -1.2 ± 5.8%, 0.1 ± 3.5%, and 0.0 ± 2.5%, respectively. The corresponding results for total lung mass were -1.1 ± 5.9%, 0.0 ± 3.5%, and 0.0 ± 3.0%. The average time for analysis of one thoracic CT-scan using the interpolation method was 1.5-2 h compared to 8 h for analysis of all images of one complete thoracic CT-scan. The calculation of pulmonary qCTA data by interpolation from 12 CT-images was applicable for equine lung CT-scans and reduced the time required for analysis by 75%. Copyright © 2014 Elsevier Ltd. All rights reserved.

Growth kinetics and physiological behavior of co-cultures of Saccharomyces cerevisiae and Kluyveromyces lactis, fermenting carob sugars extracted with whey.

PubMed

Rodrigues, B; Lima-Costa, M E; Constantino, A; Raposo, S; Felizardo, C; Gonçalves, D; Fernandes, T; Dionísio, L; Peinado, J M

2016-10-01

Alcoholic fermentation of carob waste sugars (sucrose, glucose and fructose) extracted with cheese whey, by co-cultures of Saccharomyces cerevisiae and Kluyveromyces lactis has been analyzed. Growth and fermentation of S. cerevisiae in the carob-whey medium showed an inhibition of about 30% in comparison with water-extracted carob. The inhibition of K. lactis on carob-whey was greater (70%) when compared with the whey medium alone, due to osmolarity problems. Oxygen availability was a very important factor for K. lactis, influencing its fermentation performance. When K. lactis was grown alone on carob-whey medium, lactose was always consumed first, and glucose and fructose were consumed afterwards, only at high aeration conditions. In co-culture with S. cerevisiae, K. lactis was completely inhibited and, at low aeration, died after 3 days; at high aeration this culture could survive but growth and lactose fermentation were only recovered after S. cerevisiae became stationary. To overcome the osmolarity and K. lactis' oxygen problems, the medium had to be diluted and a sequential fermentative process was designed in a STR-3l reactor. K. lactis was inoculated first and, with low aeration (0.13vvm), consumed all the lactose in 48h. Then S. cerevisiae was inoculated, consuming the total of the carob sugars, and producing ethanol in a fed-batch regime. The established co-culture with K. lactis increased S. cerevisiae ethanol tolerance. This fermentation process produced ethanol with good efficiency (80g/l final concentration and a conversion factor of 0.4g ethanol/g sugar), eliminating all the sugars of the mixed waste. These efficient fermentative results pointed to a new joint treatment of agro-industrial wastes which may be implemented successfully, with economic and environmental sustainability for a bioethanol industrial proposal. Copyright © 2016 Elsevier Inc. All rights reserved.

Characterization and modelling of the heat transfers in a pilot-scale reactor during composting under forced aeration.

PubMed

de Guardia, A; Petiot, C; Benoist, J C; Druilhe, C

2012-06-01

The paper focused on the modelling of the heat transfers during composting in a pilot-scale reactor under forced aeration. The model took into account the heat production and the transfers by evaporation, convection between material and gas crossing the material, conduction and surface convection between gas and material in bottom and upper parts of the reactor. The model was adjusted thanks to the measurements practised during fifteen composting experiments in which five organic wastes were, each, composted under three constant aeration rates. Heat production was considered proportional to oxygen consumption rate and the enthalpy per mole oxygen consumed was assumed constant. The convective heat transfer coefficients were determined on basis of the continuous measurements of the temperatures of both the lid and the bottom part of the reactor. The model allowed a satisfying prediction of the temperature of the composting material. In most cases, the mean absolute discard between the experimental and the simulated temperatures was inferior to 2.5°C and the peaks of temperature occurred with less than 8h delay. For the half of the experiments the temperature discard between the simulated peak and the experimental one was inferior to 5°C. On basis of the calculation of a stoichiometric production of water through oxidation of the biodegradable organic matter, the simulation of water going out from material as vapour also allowed a rather satisfying prediction of the mass of water in final mixture. The influence of the aeration rate on every type of heat loss was characterized. Finally, the model was used to evaluate the impacts on material temperature caused by the change of the insulation thickness, the ambient temperature, take the lid away, the increase or the decrease of the mass of waste to compost. Copyright © 2012 Elsevier Ltd. All rights reserved.

Characterization and modelling of the heat transfers in a pilot-scale reactor during composting under forced aeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guardia, A. de, E-mail: amaury.de-guardia@irstea.fr; Universite Europeenne de Bretagne, F-35000 Rennes; Petiot, C.

2012-06-15

The paper focused on the modelling of the heat transfers during composting in a pilot-scale reactor under forced aeration. The model took into account the heat production and the transfers by evaporation, convection between material and gas crossing the material, conduction and surface convection between gas and material in bottom and upper parts of the reactor. The model was adjusted thanks to the measurements practised during fifteen composting experiments in which five organic wastes were, each, composted under three constant aeration rates. Heat production was considered proportional to oxygen consumption rate and the enthalpy per mole oxygen consumed was assumedmore » constant. The convective heat transfer coefficients were determined on basis of the continuous measurements of the temperatures of both the lid and the bottom part of the reactor. The model allowed a satisfying prediction of the temperature of the composting material. In most cases, the mean absolute discard between the experimental and the simulated temperatures was inferior to 2.5 Degree-Sign C and the peaks of temperature occurred with less than 8 h delay. For the half of the experiments the temperature discard between the simulated peak and the experimental one was inferior to 5 Degree-Sign C. On basis of the calculation of a stoichiometric production of water through oxidation of the biodegradable organic matter, the simulation of water going out from material as vapour also allowed a rather satisfying prediction of the mass of water in final mixture. The influence of the aeration rate on every type of heat loss was characterized. Finally, the model was used to evaluate the impacts on material temperature caused by the change of the insulation thickness, the ambient temperature, take the lid away, the increase or the decrease of the mass of waste to compost.« less