Self-inhibition can limit biologically enhanced TCE dissolution from a TCE DNAPL.

PubMed

Haest, P J; Springael, D; Seuntjens, P; Smolders, E

2012-11-01

Biodegradation of trichloroethene (TCE) near a Dense Non Aqueous Phase Liquid (DNAPL) can enhance the dissolution rate of the DNAPL by increasing the concentration gradient at the DNAPL-water interface. Two-dimensional flow-through sand boxes containing a TCE DNAPL and inoculated with a TCE dechlorinating consortium were set up to measure this bio-enhanced dissolution under anaerobic conditions. The total mass of TCE and daughter products in the effluent of the biotic boxes was 3-6 fold larger than in the effluent of the abiotic box. However, the mass of daughter products only accounted for 19-55% of the total mass of chlorinated compounds in the effluent, suggesting that bio-enhanced dissolution factors were maximally 1.3-2.2. The enhanced dissolution most likely primarily resulted from variable DNAPL distribution rather than biodegradation. Specific dechlorination rates previously determined in a stirred liquid medium were used in a reactive transport model to identify the rate limiting factors. The model adequately simulated the overall TCE degradation when predicted resident microbial numbers approached observed values and indicated an enhancement factor for TCE dissolution of 1.01. The model shows that dechlorination of TCE in the 2D box was limited due to the short residence time and the self-inhibition of the TCE degradation. A parameter sensitivity analysis predicts that the bio-enhanced dissolution factor for this TCE source zone can only exceed a value of 2 if the TCE self-inhibition is drastically reduced (when a TCE tolerant dehalogenating community is present) or if the DNAPL is located in a low-permeable layer with a small Darcy velocity. Copyright © 2012 Elsevier Ltd. All rights reserved.

ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES

EPA Science Inventory

Electrochemical dechlorination of TCE ws conducted in a glass column using granular graphite as electrodes. A constant voltage of 15 volt was applied resulting in 60-62 mA of current. Approximately 4-6% of the TCE was dechlorinated. Among the reduced TCE, more than 95% was comple...

ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES

EPA Science Inventory

Electrochemical dechlorination of TCE was conducted in a glass column using granular graphite as electrodes. A constant voltage of 15 volt was applied resulting in 60-62 mA of current. Approximately 4-6% of the TCE was dechlorinated. Among the reduced TCE, more than 95% was compl...

EFFECTS OF REACTOR CONDITIONS ON ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODE

EPA Science Inventory

Trichloroethylene (TCE) was electrochemically dechlorinated in aqueous environments using granular graphite cathode in a mixed reactor. Effects of pH, current, electrolyte type, and flow rate on TCE dechlorination rate were evaluated. TCE dechlorination rate constant and gas pr...

EFFECTS OF REACTOR CONDITIONS ON ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODE.

EPA Science Inventory

Trichloroethylene (TCE) was electrochemically dechlorinated in aqueous environments using granular graphite cathode in a mixed reactor. Effects of pH, current, electrolyte type, and flow rate on TCE dechlorination rate were evaluated. TCE dechlorination rate constant and gas pr...

EFFECTS OF REACTION PARAMETERS ON ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE RATE AND BY-PRODUCTS

EPA Science Inventory

Trichloroethylene (TCE) was electrochemically dechlorinated in aqueous environments using granular graphite cathode in a mixed reactor. Effects of pH, current, electrolyte type, and flow rate on TCE dechlorination rate were evaluated. TCE dechlorination rate constant and gas prod...

Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach.

PubMed

Freitas, Juliana G; Rivett, Michael O; Roche, Rachel S; Durrant Neé Cleverly, Megan; Walker, Caroline; Tellam, John H

2015-02-01

The typically elevated natural attenuation capacity of riverbed-hyporheic zones is expected to decrease chlorinated hydrocarbon (CHC) groundwater plume discharges to river receptors through dechlorination reactions. The aim of this study was to assess physico-chemical processes controlling field-scale variation in riverbed-hyporheic zone dechlorination of a TCE groundwater plume discharge to an urban river reach. The 50-m long pool-riffle-glide reach of the River Tame in Birmingham (UK) studied is a heterogeneous high energy river environment. The shallow riverbed was instrumented with a detailed network of multilevel samplers. Freeze coring revealed a geologically heterogeneous and poorly sorted riverbed. A chlorine number reduction approach provided a quantitative indicator of CHC dechlorination. Three sub-reaches of contrasting behaviour were identified. Greatest dechlorination occurred in the riffle sub-reach that was characterised by hyporheic zone flows, moderate sulphate concentrations and pH, anaerobic conditions, low iron, but elevated manganese concentrations with evidence of sulphate reduction. Transient hyporheic zone flows allowing input to varying riverbed depths of organic matter are anticipated to be a key control. The glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition, absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to locally inhibit dechlorination. The tail-of-pool-riffle sub-reach exhibited patchy dechlorination that was attributed to sub-reach complexities including significant flow bypass of a low permeability, high organic matter, silty unit of high dechlorination potential. A process-based conceptual model of reach-scale dechlorination variability was developed. Key findings of practitioner relevance were: riverbed-hyporheic zone CHC dechlorination may provide only a partial, somewhat patchy barrier to CHC

HORIZONTAL LASAGNA TO BIOREMEDIATE TCE

EPA Science Inventory

Removal of TCE from these tight clay soils has been technically difficult and expensive. However, the LASAGNATM technique allows movement of the TCE into treatment zones for biodegradation or dechlorination in place, lessening the costs and exposure to TCE. Electroosmosis was c...

MODELING THE ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE IN A GRANULAR GRAPHITE-PACKED REACTOR

EPA Science Inventory

A comprehensive reactor model was developed for the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite cathode. The reactor model describes the dynamic processes of TCE dechlorination and adsorption, and the formation and dechlorination of all the major...

Nature's Helpers: Using Microorganisms to Remove Trichloroethene (TCE) from Groundwater

NASA Astrophysics Data System (ADS)

Delgado, A. G.; Krajmlanik-Brown, R.; Fajardo-Williams, D.; Halloum, I.

2015-12-01

Organic chlorinated solvents, such as perchloroethene (PCE) and trichloroethene (TCE), are toxic pollutants threatening ground water quality worldwide and present at many superfund sites. Bioremediation using microorganisms is a promising, green, efficient, and sustainable approach to remove PCE and TCE contamination from soil and groundwater. Under anaerobic conditions, specialized microorganisms (dechlorinators) can reduce these chlorinated ethenes to ethene, an innocuous product, and gain energy for growth by a process known as reductive dechlorination. Dechlorinators are most often present in the environment and in dechlorinating cultures alongside other microbes such as fermenters, methanogens, and acetogens. Fermenters, methanogens, and acetogens syntrophically provide essential nutrients and growth factors to dechlorinators, most specifically to the only members able to reduce TCE all the way to ethene: Dehalococcoides; unfortunately, they also compete with dechlorinators for electron donors. My laboratory devises reductive chlorination platforms to study competition and syntrophy among Dehalococcoides, and other microbes to optimize remediation reactions and transport in the subsurface. We look at competing processes present as part of the natural soil chemistry and microbiology and address these challenges through a combination of enrichment techniques, molecular microbial ecology (deep sequencing), water chemistry, and electron balances. We have applied knowledge gathered in my laboratory to: 1) enrich microbial dechlorinating cultures capable of some of the fastest rates of TCE to ethene dechlorination ever reported, and 2) successfully design and operate three different continuous dechlorinating reactor types. We attribute our successful reactor operations to our multidisciplinary approach which links microbiology and engineering. Our reactors produce robust dechlorinating cultures used for in-situ bioaugmentation of PCE and TCE at contaminated sites

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Q.; Muftikian, R.; Korte, N.

1998-06-02

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds. 10 figs.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Q.; Muftikian, R.; Korte, N.

1997-03-18

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds. 10 figs.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1997-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1998-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds.

Phylogenetic characterization of microbial communities that reductively dechlorinate TCE based upon a combination of molecular techniques.

PubMed

Richardson, Ruth E; Bhupathiraju, Vishvesh K; Song, Donald L; Goulet, Tanuja A; Alvarez-Cohen, Lisa

2002-06-15

An anaerobic microbial consortium (referred to as ANAS) that reductively dechlorinates trichloroethene (TCE) completely to ethene with the transient production of cisdichloroethene (cDCE) and vinyl chloride was enriched from contaminated soil obtained from Alameda Naval Air Station. ANAS uses lactate as its electron donor and has been functionally stable for over 2 years. Following a brief exposure to oxygen, a subculture (designated VCC) derived from ANAS could dechlorinate TCE only to vinyl chloride with lactate as its electron donor. Three molecular methods were used concurrently to characterize the community structure of ANAS and VCC: clone library construction/clone sequencing, terminal restriction fragment length polymorphism (T-RFLP) analysis, and fluorescent in situ hybridization (FISH) with rRNA probes. The community structure of ANAS did not change significantly over the course of a single feeding/dechlorination cycle, and only minor fluctuations occurred over many feeding cycles spanning the course of 1 year. Clone libraries and T-RFLP analyses suggested that ANAS was dominated by populations belonging to three phylogenetic groups: Dehalococcoides species, Desulfovibrio species, and members of the Clostridiaceae (within the low G + C Gram-positives). FISH results suggest that members of the Cytophaga/Flavobacterium/Bacteroides (CFB) cluster and high G + C Gram-positives (HGCs) were numerically important in ANAS despite their under-representation in the clone libraries. Parallel analyses of VCC samples suggested that Dehalococcoides species and Clostridiaceae were only minor populations in this community. Instead, VCC had increased populations of organisms in the beta and gamma subclasses of the Proteobacteria as well as significant populations of organisms in the CFB cluster. It is possible that symbiotic interactions are occurring between some of ANAS's phylogenetic groups under the enrichment conditions, including interspecies hydrogen transfer from

HORIZONTAL LASAGNA^TM TO BIOREMEDIATE TCE

EPA Science Inventory

Removal of TCE from these tight clay soils has been technically difficult and expensive. However, the LASAGNA technique allows movement of the TCE into treatment zones for biodegradation or dechlorination in place, lessening the costs and exposure to TCE.

Electroosmosis wa...

Investigating the biogeochemical interactions involved in simultaneous TCE and Arsenic in situ bioremediation

NASA Astrophysics Data System (ADS)

Cook, E.; Troyer, E.; Keren, R.; Liu, T.; Alvarez-Cohen, L.

2016-12-01

The in situ bioremediation of contaminated sediment and groundwater is often focused on one toxin, even though many of these sites contain multiple contaminants. This reductionist approach neglects how other toxins may affect the biological and chemical conditions, or vice versa. Therefore, it is of high value to investigate the concurrent bioremediation of multiple contaminants while studying the microbial activities affected by biogeochemical factors. A prevalent example is the bioremediation of arsenic at sites co-contaminated with trichloroethene (TCE). The conditions used to promote a microbial community to dechlorinate TCE often has the adverse effect of inducing the release of previously sequestered arsenic. The overarching goal of our study is to simultaneously evaluate the bioremediation of arsenic and TCE. Although TCE bioremediation is a well-understood process, there is still a lack of thorough understanding of the conditions necessary for effective and stable arsenic bioremediation in the presence of TCE. The objective of this study is to promote bacterial activity that stimulates the precipitation of stable arsenic-bearing minerals while providing anaerobic, non-extreme conditions necessary for TCE dechlorination. To that end, endemic microbial communities were examined under various conditions to attempt successful sequestration of arsenic in addition to complete TCE dechlorination. Tested conditions included variations of substrates, carbon source, arsenate and sulfate concentrations, and the presence or absence of TCE. Initial arsenic-reducing enrichments were unable to achieve TCE dechlorination, probably due to low abundance of dechlorinating bacteria in the culture. However, favorable conditions for arsenic precipitation in the presence of TCE were eventually discovered. This study will contribute to the understanding of the key species in arsenic cycling, how they are affected by various concentrations of TCE, and how they interact with the key

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Quintus; Muftikian, Rosy; Korte, Nic

1997-01-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from various effluents or contaminated soil containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products.

Use of emulsified vegetable oil to support bioremediation of TCE DNAPL in soil columns.

PubMed

Harkness, Mark; Fisher, Angela

2013-08-01

The interaction between emulsified vegetable oil (EVO) and trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) was observed using two soil columns and subsequent reductive dechlorination of TCE was monitored over a three year period. Dyed TCE DNAPL (~75 g) was emplaced in one column (DNAPL column), while the second was DNAPL-free (plume column). EVO was added to both columns and partitioning of the EVO into the TCE DNAPL was measured and quantified. TCE (1.9 mM) was added to the influent of the plume column to simulate conditions down gradient of a DNAPL source area and the columns were operated independently for more than one year, after which they were connected in series. Initially limited dechlorination of TCE to cDCE was observed in the DNAPL column, while the plume column supported complete reductive dechlorination of TCE to ethene. Upon connection and reamendment of the plume column with EVO, near saturation levels of TCE from the effluent of the DNAPL column were rapidly dechlorinated to c-DCE and VC in the plume column; however, this high rate dechlorination produced hydrochloric acid which overwhelmed the buffering capacity of the system and caused the pH to drop below 6.0. Dechlorination efficiency in the columns subsequently deteriorated, as measured by the chloride production and Dehalococcoides counts, but was restored by adding sodium bicarbonate buffer to the influent groundwater. Robust dechlorination was eventually observed in the DNAPL column, such that the TCE DNAPL was largely removed by the end of the study. Partitioning of the EVO into the DNAPL provided significant operational benefits to the remediation system both in terms of electron donor placement and longevity. Copyright © 2013 Elsevier B.V. All rights reserved.

Dechlorination of TCE with palladized iron

DOEpatents

Fernando, Q.; Muftikian, R.; Korte, N.

1997-04-01

The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from various effluents or contaminated soil containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. 10 figs.

Comparison of Chlorinated Ethenes DNAPL Reductive Dechlorination by Indigenous and Evanite culture with Surfactant Tween-80

NASA Astrophysics Data System (ADS)

Kwon, S.; Hong, S.; Kim, R.; Kim, N.; Ahn, H.; Lee, S.; Kim, Y.

2010-12-01

Although many innovative technologies have been developed to enhance remediation of chlorinated ethenes(e.g. tetrachloroethene[PCE], trichloroethene[TCE])DNAPL source zones, they have been ineffective in reducing contaminant concentration to regulatory end points. Thus, combination of surfactant flushing process that removes significant contaminant mass with microbial reductive dechlorination, posttreatment "polishing step" to control the remaining DNAPL that may serve as a source of reducing equivalents and stimulate the dechlorinating bacterial communities may be an attractive remediation process alternatively. Microcosm studies were conducted to explore chlorinated ethenes, PCE/TCE of 3 ~ 30 mg/L dechlorination by indigenous microbial communities from TCE DNAPL source zones of Korea and Evanite culture in the presence of Tween-80 of 10 ~ 5,000 mg/L. In the microcosms for indigenous microbial communities, by-products(e.g. c-DCE, vinyl chloride) of reductive dechlorination of PCE/TCE were not detected. This results suggest dechlorinating bacteria might be not exist or high concentration of chlorinated ethenes inhibit activity of dechlorinating bacteria in indigenous microbial communities. But VFAs like acetate, methane and hydrogen gas from fermentation of Tween-80 were detected. So Tween-80 might estimated to serve as a source of reducing equivalents. To evaluate the dechlorinating ability of Evanite-culture, we added Evanite-culture to the microcosms for indigenous bacteria and monitored by-products of reductive dechlorination of PCE/TCE and VFAs and hydrogen gas.

Effects of 1,1,1-Trichloroethane and Triclocarban on Reductive Dechlorination of Trichloroethene in a TCE-Reducing Culture

PubMed Central

Wen, Li-Lian; Chen, Jia-Xian; Fang, Jia-Yi; Li, Ang; Zhao, He-Ping

2017-01-01

Chlorinated compounds were generally present in the environment due to widespread use in the industry. A short-term study was performed to evaluate the effects of 1,1,1- trichloroethane (TCA) and triclocarban (TCC) on trichloroethene (TCE) removal in a reactor fed with lactate as the sole electron donor. Both TCA and TCC inhibited TCE reduction, but the TCC had a more pronounced effect compared to TCA. The TCE-reducing culture, which had never been exposed to TCA before, reductively dechlorinated TCA to 1,1-dichloroethane (DCA). Below 15 μM, TCA had little effect on the transformation of TCE to cis-dichloroethene (DCE); however, the reduction of cis-DCE and vinyl chloride (VC) were more sensitive to TCA, and ethene production was completely inhibited when the concentration of TCA was above 15 μM. In cultures amended with TCC, the reduction of TCE was severely affected, even at concentrations as low as 0.3 μM; all the cultures stalled at VC, and no ethene was detected. The cultures that fully transformed TCE to ethene contained 5.2–8.1% Dehalococcoides. Geobacter and Desulfovibrio, the bacteria capable of partially reducing TCE to DCE, were detected in all cultures, but both represented a larger proportion of the community in TCC-amended cultures. All cultures were dominated by Clostridium_sensu_stricto_7, a genus that belongs to Firmicutes with proportions ranging from 40.9% (in a high TCC (15 μM) culture) to 88.2%. Methanobacteria was detected at levels of 1.1–12.7%, except in cultures added with 15 and 30 μM TCA, in which they only accounted for ∼0.4%. This study implies further environmental factors needed to be considered in the successful bioremediation of TCE in contaminated sites. PMID:28824572

Effects of 1,1,1-Trichloroethane and Triclocarban on Reductive Dechlorination of Trichloroethene in a TCE-Reducing Culture.

PubMed

Wen, Li-Lian; Chen, Jia-Xian; Fang, Jia-Yi; Li, Ang; Zhao, He-Ping

2017-01-01

Chlorinated compounds were generally present in the environment due to widespread use in the industry. A short-term study was performed to evaluate the effects of 1,1,1- trichloroethane (TCA) and triclocarban (TCC) on trichloroethene (TCE) removal in a reactor fed with lactate as the sole electron donor. Both TCA and TCC inhibited TCE reduction, but the TCC had a more pronounced effect compared to TCA. The TCE-reducing culture, which had never been exposed to TCA before, reductively dechlorinated TCA to 1,1-dichloroethane (DCA). Below 15 μM, TCA had little effect on the transformation of TCE to cis -dichloroethene (DCE); however, the reduction of cis -DCE and vinyl chloride (VC) were more sensitive to TCA, and ethene production was completely inhibited when the concentration of TCA was above 15 μM. In cultures amended with TCC, the reduction of TCE was severely affected, even at concentrations as low as 0.3 μM; all the cultures stalled at VC, and no ethene was detected. The cultures that fully transformed TCE to ethene contained 5.2-8.1% Dehalococcoides . Geobacter and Desulfovibrio , the bacteria capable of partially reducing TCE to DCE, were detected in all cultures, but both represented a larger proportion of the community in TCC-amended cultures. All cultures were dominated by Clostridium _sensu_stricto_7, a genus that belongs to Firmicutes with proportions ranging from 40.9% (in a high TCC (15 μM) culture) to 88.2%. Methanobacteria was detected at levels of 1.1-12.7%, except in cultures added with 15 and 30 μM TCA, in which they only accounted for ∼0.4%. This study implies further environmental factors needed to be considered in the successful bioremediation of TCE in contaminated sites.

Evidence of rock matrix back-diffusion and abiotic dechlorination using a field testing approach

NASA Astrophysics Data System (ADS)

Schaefer, Charles E.; Lippincott, David R.; Klammler, Harald; Hatfield, Kirk

2018-02-01

An in situ field demonstration was performed in fractured rock impacted with trichloroethene (TCE) and cis-1,2-dichloroethene (DCE) to assess the impacts of contaminant rebound after removing dissolved contaminants within hydraulically conductive fractures. Using a bedrock well pair spaced 2.4 m apart, TCE and DCE were first flushed with water to create a decrease in dissolved contaminant concentrations. While hydraulically isolating the well pair from upgradient contaminant impacts, contaminant rebound then was observed between the well pair over 151 days. The magnitude, but not trend, of TCE rebound was reasonably described by a matrix back-diffusion screening model that employed an effective diffusion coefficient and first-order abiotic TCE dechlorination rate constant that was based on bench-scale testing. Furthermore, a shift in the TCE:DCE ratio and carbon isotopic enrichment was observed during the rebound, suggesting that both biotic and abiotic dechlorination were occurring within the rock matrix. The isotopic data and back-diffusion model together served as a convincing argument that matrix back-diffusion was the mechanism responsible for the observed contaminant rebound. Results of this field demonstration highlight the importance and applicability of rock matrix parameters determined at the bench-scale, and suggest that carbon isotopic enrichment can be used as a line of evidence for abiotic dechlorination within rock matrices.

Reductive dechlorination of trichloroethene mediated by humic-metal complexes

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

O`Loughlin, E.J.; Burris, D.R.; Delcomyn, C.A.

1999-04-01

Experiments were conducted to determine if transition metal-humic acid complexes can act as e{sup {minus}} transfer mediators in the reductive dechlorination of trichloroethene (TCE) using Ti(III) citrate as the bulk reductant. In the presence of Ni-Aldrich humic acid (AHA) complexes, TCE reduction was rapid, with complete removal of TCE in less than 23 h. Cu-AHA complexes were less effective as e{sup {minus}} mediators than Ni-AHA complexes; only 60% of TCE was reduced after 150 h. Partially dechlorinated intermediates were observed during TCE reduction; however, they were transitory, and at no time accounted for more than 2% of the initial TCEmore » mass on a mole C basis. Ethane and ethene were the primary end products of TCE reduction; however, a suite of other non-chlorinated hydrocarbons consisting of methane and C{sub 3} to C{sub 6} alkanes and alkenes were also observed. The results suggest that humic-metal complexes may represent a previously unrecognized class of electron mediators in natural environments.« less

Mechanochemically Sulfidated Microscale Zero Valent Iron: Pathways, Kinetics, Mechanism, and Efficiency of Trichloroethylene Dechlorination.

PubMed

Gu, Yawei; Wang, Binbin; He, Feng; Bradley, Miranda J; Tratnyek, Paul G

2017-11-07

In water treatment processes that involve contaminant reduction by zerovalent iron (ZVI), reduction of water to dihydrogen is a competing reaction that must be minimized to maximize the efficiency of electron utilization from the ZVI. Sulfidation has recently been shown to decrease H 2 formation significantly, such that the overall electron efficiency of (or selectivity for) contaminant reduction can be greatly increased. To date, this work has focused on nanoscale ZVI (nZVI) and solution-phase sulfidation agents (e.g., bisulfide, dithionite or thiosulfate), both of which pose challenges for up-scaling the production of sulfidated ZVI for field applications. To overcome these challenges, we developed a process for sulfidation of microscale ZVI by ball milling ZVI with elemental sulfur. The resulting material (S-mZVI bm ) exhibits reduced aggregation, relatively homogeneous distribution of Fe and S throughout the particle (not core-shell structure), enhanced reactivity with trichloroethylene (TCE), less H 2 formation, and therefore greatly improved electron efficiency of TCE dechlorination (ε e ). Under ZVI-limited conditions (initial Fe 0 /TCE = 1.6 mol/mol), S-mZVI bm gave surface-area normalized reduction rate constants (k' SA ) and ε e that were ∼2- and 10-fold greater than the unsulfidated ball-milled control (mZVI bm ). Under TCE-limited conditions (initial Fe 0 /TCE = 2000 mol/mol), sulfidation increased k SA and ε e ≈ 5- and 50-fold, respectively. The major products from TCE degradation by S-mZVI bm were acetylene, ethene, and ethane, which is consistent with dechlorination by β-elimination, as is typical of ZVI, iron oxides, and/or sulfides. However, electrochemical characterization shows that the sulfidated material has redox properties intermediate between ZVI and Fe 3 O 4 , mostly likely significant coverage of the surface with FeS.

Reductive dechlorination of trichloroethylene by iron bimetallics

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

Orth, R.G.; Dauda, T.; McKenzie, D.E.

1998-07-01

Reductive dechlorination using a zero valence metal such as iron has seen an increase in interest with the extension of iron dechlorination to in-situ treatment of ground water. Studies to increase the rate of dechlorination and the long term stability have lead many to examine the use of bimetallic iron systems. Results are shown for bimetallic iron systems of Cu, Sn, Ni, Ag, Au, and Pd. All of these bimetallic couples form a galvanic couple which increase corrosion rates and the production of hydrogen. Increased rates of reaction normalized to surface area were observed for all the couples. The reactionmore » rates were found to depended on surface area and surface coverage of the iron. The results of studies in deuterium oxide indicate that the pathways changed as the bimetallic is changed and that the pathway in all cases could be a combination of dehydrohalgenation and sequential dechlorination. Degradation of DNAPL TCE by iron was found to be zero order and the type of product observed was different from that observed for TCE dissolved in water.« less

Influence of Different Electron Donors and Acceptors on Dehalorespiration of Tetrachloroethene by Desulfitobacterium frappieri TCE1

PubMed Central

Gerritse, Jan; Drzyzga, Oliver; Kloetstra, Geert; Keijmel, Mischa; Wiersum, Luit P.; Hutson, Roger; Collins, Matthew D.; Gottschal, Jan C.

1999-01-01

Strain TCE1, a strictly anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene (PCE) and trichloroethene (TCE), was isolated by selective enrichment from a PCE-dechlorinating chemostat mixed culture. Strain TCE1 is a gram-positive, motile, curved rod-shaped organism that is 2 to 4 by 0.6 to 0.8 μm and has approximately six lateral flagella. The pH and temperature optima for growth are 7.2 and 35°C, respectively. On the basis of a comparative 16S rRNA sequence analysis, this bacterium was identified as a new strain of Desulfitobacterium frappieri, because it exhibited 99.7% relatedness to the D. frappieri type strain, strain PCP-1. Growth with H2, formate, l-lactate, butyrate, crotonate, or ethanol as the electron donor depends on the availability of an external electron acceptor. Pyruvate and serine can also be used fermentatively. Electron donors (except formate and H2) are oxidized to acetate and CO2. When l-lactate is the growth substrate, strain TCE1 can use the following electron acceptors: PCE and TCE (to produce cis-1,2-dichloroethene), sulfite and thiosulfate (to produce sulfide), nitrate (to produce nitrite), and fumarate (to produce succinate). Strain TCE1 is not able to reductively dechlorinate 3-chloro-4-hydroxyphenylacetate. The growth yields of the newly isolated bacterium when PCE is the electron acceptor are similar to those obtained for other dehalorespiring anaerobes (e.g., Desulfitobacterium sp. strain PCE1 and Desulfitobacterium hafniense) and the maximum specific reductive dechlorination rates are 4 to 16 times higher (up to 1.4 μmol of chloride released · min−1 · mg of protein−1). Dechlorination of PCE and TCE is an inducible process. In PCE-limited chemostat cultures of strain TCE1, dechlorination is strongly inhibited by sulfite but not by other alternative electron acceptors, such as fumarate or nitrate. PMID:10583967

Anaerobic reductive dechlorination of tetrachloroethene: how can dual Carbon-Chlorine isotopic measurements help elucidating the underlying reaction mechanism?

NASA Astrophysics Data System (ADS)

Badin, Alice; Buttet, Géraldine; Maillard, Julien; Holliger, Christof; Hunkeler, Daniel

2014-05-01

Chlorinated ethenes (CEs) such as tetrachloroethene (PCE) are common persistent groundwater contaminants. Among clean-up strategies applied to sites affected by such pollution, bioremediation has been considered with a growing interest as it represents a cost-effective, environmental friendly approach. This technique however sometimes leads to an incomplete and slow biodegradation of CEs resulting in an accumulation of toxic metabolites. Understanding the reaction mechanisms underlying anaerobic reductive dechlorination would thus help assessing PCE biodegradation in polluted sites. Stable isotope analysis can provide insight into reaction mechanisms. For chlorinated hydrocarbons, carbon (C) and chlorine (Cl) isotope data (δ13C and δ37Cl) tend to show a linear correlation with a slope (m ≡ ɛC/ɛCl) characteristic of the reaction mechanism [1]. This study hence aims at exploring the potential of a dual C-Cl isotope approach in the determination of the reaction mechanisms involved in PCE reductive dechlorination. C and Cl isotope fractionation were investigated during anaerobic PCE dechlorination by two bacterial consortia containing members of the Sulfurospirillum genus. The specificity in these consortia resides in the fact that they each conduct PCE reductive dechlorination catalysed by one different reductive dehalogenase, i.e. PceADCE which yields trichloroethene (TCE) and cis-dichloroethene (cDCE), and PceATCE which yields TCE only. The bulk C isotope enrichment factors were -3.6±0.3 o for PceATCE and -0.7±0.1o for PceADCE. The bulk Cl isotope enrichment factors were -1.3±0.2 o for PceATCE and -0.9±0.1 o for PceADCE. When applying the dual isotope approach, two m values of 2.7±0.1 and 0.7±0.2 were obtained for the reductive dehalogenases PceATCE and PceADCE, respectively. These results suggest that PCE can be degraded according to two different mechanisms. Furthermore, despite their highly similar protein sequences, each reductive dehalogenase seems

Comparison of Reductive Dechlorination of Chlorinated Ethylene in Batch and Continuous-Flow Reactor

NASA Astrophysics Data System (ADS)

Park, S.; Jonghwan, L.; Hong, U.; Kim, N.; Ahn, H.; Lee, S.; Kim, Y.

2010-12-01

A 1.28 L-Batch reactor and continuous-flow stirred tank reactor (CFSTR) fed with formate and trichloriethene (TCE) were operated for 120 days and 72 days, respectively, to study the effect of formate as electron donor on reductive dechlorination of TCE to cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethylene (ETH). In batch reactor, injected 60 μmol TCE was completely degraded in presence of 20% hydrogen gas (H2) in less than 8 days by Evanite culture (300 mg-soluble protein) with ability to completely degrade tetrachloroethene (PCE) and TCE to ETH under anaerobic conditions. To determine the effect of formate as electron donor instead of H2, about 3 or 11 mmol of formate injected into batch-reactor every 15 days was enough to support H2 for dechlorination of c-DCE to VC and ETH. Soluble protein concentration of Evanite culture during the batch test increased from 300 mg to 688 mg for 120 days. In CFSTR test, TCE was fed continuously at 9.9 ppm (75.38 μmol/L) and the influent formate feed concentration increased stepwise from 1.3 mmol/L to 14.3 mmol/L. Injected TCE was accumulated at HRT 18 days for 13 days, but TCE was completed degraded at HRT 36 days without accumulation during left of experiment period, getting H2 from fermentative hydrogen production of injected formate. Although c-DCE was also accumulated for 23 days after CFSTR operation, it reached steady-state without accumulation in presence of excessive formate. However, since c-DCE in CFSTR was not completely dechlorinated, we will determine the transcriptional level of enzyme involved in reductive dechlorination of TCE, c-DCE, and VC in our future work.

Low and high acetate amendments are equally as effective at promoting complete dechlorination of trichloroethylene (TCE).

PubMed

Wei, Na; Finneran, Kevin T

2013-06-01

Experiments with trichloroethylene-contaminated aquifer material demonstrated that TCE, cis-DCE, and VC were completely degraded with concurrent Fe(III) or Fe(III) and sulfate reduction when acetate was amended at stoichiometric concentration; competing TEAPs did not inhibit ethene production. Adding 10× more acetate did not increase the rate or extent of TCE reduction, but only increased methane production. Enrichment cultures demonstrated that ~90 μM TCE or ~22 μM VC was degraded primarily to ethene within 20 days with concurrent Fe(III) or Fe(III) + sulfate reduction. The dechlorination rates were comparable between the low and high acetate concentrations (0.36 vs 0.34 day(-1), respectively), with a slightly slower rate in the 10× acetate amended incubations. Methane accumulated to 13.5 (±0.5) μmol/tube in the TCE-degrading incubations with 10× acetate, and only 1.4 (±0.1) μmol/tube with low acetate concentration. Methane accumulated to 16 (±1.5) μmol/tube in VC-degrading enrichment with 10× acetate and 2 (±0.1) μmol/tube with stoichiometric acetate. The estimated fraction of electrons distributed to methanogenesis increased substantially when excessive acetate was added. Quantitative PCR analysis indicated that 10× acetate did not enhance Dehalococcoides biomass but rather increased the methanogen abundance by nearly one order of magnitude compared to that with stoichiometric acetate. The data suggest that adding low levels of substrate may be equally if not more effective as high concentrations, without producing excessive methane. This has implications for field remediation efforts, in that adding excess electron donor may not benefit the reactions of interest, which in turn will increase treatment costs without direct benefit to the stakeholders.

Optimization of electrochemical dechlorination of trichloroethylene in reducing electrolytes

PubMed Central

Mao, Xuhui; Ciblak, Ali; Baek, Kitae; Amiri, Mohammad; Loch-Caruso, Rita; Alshawabkeh, Akram N.

2012-01-01

Electrochemical dechlorination of trichloroethylene (TCE) in aqueous solution is investigated in a closed, liquid-recirculation system. The anodic reaction of cast iron generates ferrous species, creating a chemically reducing electrolyte (negative ORP value). The reduction of TCE on the cathode surface is enhanced under this reducing electrolyte because of the absence of electron competition. In the presence of the iron anode, the performances of different cathodes are compared in a recirculated electrolysis system. The copper foam shows superior capability for dechlorination of aqueous TCE. Electrolysis by cast iron anode and copper foam cathode is further optimized though a multivariable experimental design and analysis. The conductivity of the electrolyte is identified as an important factor for both final elimination efficiency (FEE) of TCE and specific energy consumption. The copper foam electrode exhibits high TCE elimination efficiency in a wide range of initial TCE concentration. Under coulostatic conditions, the optimal conditions to achieve the highest FEE are 9.525 mm thick copper foam electrode, 40 mA current and 0.042 mol L−1 Na2SO4. This novel electrolysis system is proposed to remediate groundwater contaminated by chlorinated organic solvents, or as an improved iron electrocoagulation process capable of treating the wastewater co-contaminated with chlorinated compounds. PMID:22264798

Dehalococcoides abundance and alternate electron acceptor effects on large, flow-through trichloroethene dechlorinating columns.

PubMed

Mirza, Babur S; Sorensen, Darwin L; Dupont, R Ryan; McLean, Joan E

2016-03-01

Trichloroethene (TCE) in groundwater is a major health concern and biostimulation/bioaugmentation-based strategies have been evaluated to achieve complete reductive dechlorination with varying success. Different carbon sources were hypothesized to stimulate different extents of TCE reductive dechlorination. Ecological conditions that developed different dechlorination stages were investigated by quantitating Dehalococcoides 16S rRNA (Dhc) and reductive dehalogenase gene abundance, and by describing biogeochemical properties of laboratory columns in response to this biostimulation. Eight large columns (183 cm × 15.2 cm), packed with aquifer material from Hill AFB, Utah, that were continuously fed TCE for 7.5 years. Duplicate columns were biostimulated with whey or one of two different Newman Zone® emulsified oil formulations containing either nonionic surfactant (EOLN) or standard surfactant (EOL). Two columns were non-stimulated controls. Complete (whey amended), partial (EOLN amended), limited (EOL), and non-TCE dehalogenating systems (controls) developed over the course of the study. Bioaugmentation of half of the columns with Bachman Road culture 3 years prior to dismantling did not influence the extent of TCE dehalogenation. Multivariate analysis clustered samples by biostimulation treatments and extent of TCE dehalogenation. Dhc, tceA, and bvcA gene concentrations did not show a consistent relationship with TCE dehalogenation but the vcrA gene was more abundant in completely dehalogenating, whey-treated columns. The whey columns developed strongly reducing conditions producing Fe(II), sulfide, and methane. Biostimulation with different carbon and energy sources can support high concentrations of diverse Dhc, but carbon addition has a major influence on biogeochemical processes effecting the extent of TCE dehalogenation.

ELECTROCHEMICAL DEGRADATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES: IDENTIFICATION AND QUALIFICATION OF DECHLORINATION PRODUCTS

EPA Science Inventory

TCE was successfully dechlorinated in aqueous solution using granular graphite as the cathode in a mixed electrochemical reactor. In experiments with an initial TCE concentration of less than 100 mg/l, TCE was reduced approximately by 75% in the reactor under an applied cell volt...

Contributions of Fe Minerals to Abiotic Dechlorination

EPA Science Inventory

Most applications of enhanced in situ bioremediation are based on biological reductive dechlorination. Anaerobic metabolism can also produce reactive minerals that allow for in situ biogeochemical transformation of chlorinated organic contaminants such as PCE, TCE, and cis-DCE. ...

Comparison of PCE and TCE disappearance in heated volatile organic analysis vials and flame-sealed ampules.

PubMed

Costanza, Jed; Pennell, Kurt D

2008-02-01

The rates of hydrolysis reported for tetrachloroethylene (PCE) and trichloroethylene (TCE) at elevated temperatures range over two orders-of-magnitude, where some of the variability may be due to the presence of a gas phase. Recent studies suggest that volatile organic analysis (VOA) vials provide a low-cost and readily available zero headspace system for measuring aqueous-phase hydrolysis rates. This work involved measuring rates of PCE and TCE disappearance and the corresponding appearance of dechlorination products in water-filled VOA vials and flame-sealed ampules incubated at 21 and 55 degrees C for up to 95.5 days. While PCE and TCE concentrations readily decreased in the VOA vials to yield first-order half lives of 11.2 days for PCE and 21.1 days for TCE at 55 degrees C, concentrations of anticipated dechlorination products, including chloride, remained constant or were not detected. The rate of PCE disappearance was 34 times faster in VOA vials at 55 degrees C compared to values obtained with flame-sealed ampules containing PCE-contaminated water. In addition, the concentration of TCE increased slightly in flame-sealed ampules incubated at 55 degrees C, while a decrease in TCE levels was observed in the VOA vials. The observed losses of PCE and TCE in the VOA vials were attributed to diffusion and sorption in the septa, rather than to dechlorination. These findings demonstrate that VOA vials are not suitable for measuring rates of volatile organic compound hydrolysis at elevated temperatures.

INFLUENCES OF PH AND CURRENT ON ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE AT A GRANULAR-GRAPHITE PACKED ELECTRODE

EPA Science Inventory

Electrolytic dechlorination using a granular-graphite packed cathode is an alternative method for the remediation of chlorinated organic compounds. Its effectiveness under various conditions needs experimental investigation. Dechlorination of trichloroethylene (TCE) was conducted...

Remediation of TCE-contaminated groundwater using nanocatalyst and bacteria.

PubMed

Kang, Ser Ku; Seo, Hyunhee; Sun, Eunyoung; Kim, Inseon; Roh, Yul

2011-08-01

The objective of this study was to develop and evaluate the remediation of trichloroethene (TCE)-contaminated groundwater using both a nanocatalyst (bio-Zn-magnetite) and bacterium (similar to Clostridium quinii) in anoxic environments. Of the 7 nanocatalysts tested, bio-Zn-magnetite showed the highest TCE dechlorination efficiency, with an average of ca. 90% within 8 days in a batch experiment. The column tests confirmed that the application of bio-Zn-magnetite in combination with the bacterium achieved high degradation efficiency (ca. 90%) of TCE within 5 days compared to the nanocatalyst only, which degraded only 30% of the TCE. These results suggest that the application of a nanocatalyst and the bacterium have potential for the remediation of TCE-contaminated groundwater in subsurface environments.

Highly organic natural media as permeable reactive barriers: TCE partitioning and anaerobic degradation profile in eucalyptus mulch and compost.

PubMed

Öztürk, Zuhal; Tansel, Berrin; Katsenovich, Yelena; Sukop, Michael; Laha, Shonali

2012-10-01

Batch and column experiments were conducted with eucalyptus mulch and commercial compost to evaluate suitability of highly organic natural media to support anaerobic decomposition of trichloroethylene (TCE) in groundwater. Experimental data for TCE and its dechlorination byproducts were analyzed with Hydrus-1D model to estimate the partitioning and kinetic parameters for the sequential dechlorination reactions during TCE decomposition. The highly organic natural media allowed development of a bioactive zone capable of decomposing TCE under anaerobic conditions. The first order TCE biodecomposition reaction rates were 0.23 and 1.2d(-1) in eucalyptus mulch and compost media, respectively. The retardation factors in the eucalyptus mulch and compost columns for TCE were 35 and 301, respectively. The results showed that natural organic soil amendments can effectively support the anaerobic bioactive zone for remediation of TCE contaminated groundwater. The natural organic media are effective environmentally sustainable materials for use in permeable reactive barriers. Copyright © 2012 Elsevier Ltd. All rights reserved.

USE OF CARBON STABLE ISOTOPE TO INVESTIGATE CHLOROMETHANE FORMATION IN THE ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

EPA Science Inventory

Carbon stable isotope trichloroethylene (¹³C TCE) was used to investigate the formation of chloromethane (CM) during the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite packed cathode. A method was developed to use a conventional GC/MS to ...

Application of a long-lasting colloidal substrate with pH and hydrogen sulfide control capabilities to remediate TCE-contaminated groundwater.

PubMed

Sheu, Y T; Chen, S C; Chien, C C; Chen, C C; Kao, C M

2015-03-02

A long-lasting emulsified colloidal substrate (LECS) was developed for continuous carbon and nanoscale zero-valent iron (nZVI) release to remediate trichloroethylene (TCE)-contaminated groundwater under reductive dechlorinating conditions. The developed LECS contained nZVI, vegetable oil, surfactants (Simple Green™ and lecithin), molasses, lactate, and minerals. An emulsification study was performed to evaluate the globule droplet size and stability of LECS. The results show that a stable oil-in-water emulsion with uniformly small droplets (0.7 μm) was produced, which could continuously release the primary substrates. The emulsified solution could serve as the dispensing agent, and nZVI particles (with diameter 100-200 nm) were distributed in the emulsion evenly without aggregation. Microcosm results showed that the LECS caused a rapid increase in the total organic carbon concentration (up to 488 mg/L), and reductive dechlorination of TCE was significantly enhanced. Up to 99% of TCE (with initial concentration of 7.4 mg/L) was removed after 130 days of operation. Acidification was prevented by the production of hydroxide ion by the oxidation of nZVI. The formation of iron sulfide reduced the odor from produced hydrogen sulfide. Microbial analyses reveal that dechlorinating bacteria existed in soils, which might contribute to TCE dechlorination. Copyright © 2014 Elsevier B.V. All rights reserved.

Modeling 3D-CSIA data: Carbon, chlorine, and hydrogen isotope fractionation during reductive dechlorination of TCE to ethene.

PubMed

Van Breukelen, Boris M; Thouement, Héloïse A A; Stack, Philip E; Vanderford, Mindy; Philp, Paul; Kuder, Tomasz

2017-09-01

Reactive transport modeling of multi-element, compound-specific isotope analysis (CSIA) data has great potential to quantify sequential microbial reductive dechlorination (SRD) and alternative pathways such as oxidation, in support of remediation of chlorinated solvents in groundwater. As a key step towards this goal, a model was developed that simulates simultaneous carbon, chlorine, and hydrogen isotope fractionation during SRD of trichloroethene, via cis-1,2-dichloroethene (and trans-DCE as minor pathway), and vinyl chloride to ethene, following Monod kinetics. A simple correction term for individual isotope/isotopologue rates avoided multi-element isotopologue modeling. The model was successfully validated with data from a mixed culture Dehalococcoides microcosm. Simulation of Cl-CSIA required incorporation of secondary kinetic isotope effects (SKIEs). Assuming a limited degree of intramolecular heterogeneity of δ 37 Cl in TCE decreased the magnitudes of SKIEs required at the non-reacting Cl positions, without compromising the goodness of model fit, whereas a good fit of a model involving intramolecular CCl bond competition required an unlikely degree of intramolecular heterogeneity. Simulation of H-CSIA required SKIEs in H atoms originally present in the reacting compounds, especially for TCE, together with imprints of strongly depleted δ 2 H during protonation in the products. Scenario modeling illustrates the potential of H-CSIA for source apportionment. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

A scrutiny of heterogeneity at the TCE Source Area BioREmediation (SABRE) test site

NASA Astrophysics Data System (ADS)

Rivett, M.; Wealthall, G. P.; Mcmillan, L. A.; Zeeb, P.

2015-12-01

A scrutiny of heterogeneity at the UK's Source Area BioREmediation (SABRE) test site is presented to better understand how spatial heterogeneity in subsurface properties and process occurrence may constrain performance of enhanced in-situ bioremediation (EISB). The industrial site contained a 25 to 45 year old trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) that was exceptionally well monitored via a network of multilevel samplers and high resolution core sampling. Moreover, monitoring was conducted within a 3-sided sheet-pile cell that allowed a controlled streamtube of flow to be drawn through the source zone by an extraction well. We primarily focus on the longitudinal transect of monitoring along the length of the cell that provides a 200 groundwater point sample slice along the streamtube of flow through the DNAPL source zone. TCE dechlorination is shown to be significant throughout the cell domain, but spatially heterogeneous in occurrence and progress of dechlorination to lesser chlorinated ethenes - it is this heterogeneity in dechlorination that we primarily scrutinise. We illustrate the diagnostic use of the relative occurrence of TCE parent and daughter compounds to confirm: dechlorination in close proximity to DNAPL and enhanced during the bioremediation; persistent layers of DNAPL into which gradients of dechlorination products are evident; fast flowpaths through the source zone where dechlorination is less evident; and, the importance of underpinning flow regime understanding on EISB performance. Still, even with such spatial detail, there remains uncertainty over the dataset interpretation. These includes poor closure of mass balance along the cell length for the multilevel sampler based monitoring and points to needs to still understand lateral flows (even in the constrained cell), even greater spatial resolution of point monitoring and potentially, not easily proven, ethene degradation loss.

Fate of TCE in heated Fort Lewis soil.

PubMed

Costanza, Jed; Fletcher, Kelly E; Löffler, Frank E; Pennell, Kurt D

2009-02-01

This study explores the transformation of trichloroethene (TCE) caused by heating contaminated soil and groundwater samples obtained from the East Gate Disposal Yard (EGDY) located in Fort Lewis, WA. After field samples transferring into glass ampules and introducing 1.5 micromol of TCE, the sealed ampules were incubated at temperatures of 25, 50, and 95 degrees C for periods of up to 95.5 days. Although TCE was completely transformed into cis-1,2-dichloroethene (cis-DCE) after 42 days at 25 degrees C by microbial activity, this transformation was not observed at 50 or 95 degrees C. Chloride levels increased after 42 days at 25 degrees C corresponding to the mass of TCE transformed to cis-DCE, were constant at 50 degrees C, and increased at 95 degrees C yielding a TCE degradation half-life of 1.6-1.9 years. These findings indicate that indigenous microbes contribute to the partial dechlorination of TCE to cis-DCE at temperatures of less than 50 degrees C, whereas interphase mass transfer and physical recovery of TCE will predominate over in situ degradation processes at temperatures of greater than 50 degrees C during thermal treatment at the EGDY site.

Electromagnetic Induction of Zerovalent Iron (ZVI) Powder and Nanoscale Zerovalent Iron (NZVI) Particles Enhances Dechlorination of Trichloroethylene in Contaminated Groundwater and Soil: Proof of Concept.

PubMed

Phenrat, Tanapon; Thongboot, Thippawan; Lowry, Gregory V

2016-01-19

This study evaluates the concept of using zerovalent iron (ZVI) powder or nanoscale zerovalent iron (NZVI) particles in combination with a low frequency (150 kHz) AC electromagnetic field (AC EMF) to effectively remove trichloroethylene (TCE) from groundwater and saturated soils. ZVI and NZVI are ferromagnetic, which can induce heat under applied AC EMF. The heat generated by ZVI and NZVI induction can increase the rate of dechlorination, according to Arrhenius' equation, and increase the rate of TCE desorption from TCE-sorbed soil. Both dechlorination and TCE desorption enhance the overall TCE removal rate. We evaluated this novel concept in laboratory batch reactors. We found that both ZVI and NZVI can induce heat under applied AC EMF up to 120 °C in 20 min. Using ZVI and NZVI with AC EMF enhanced dechlorination of dissolved TCE (no soil) up to 4.96-fold. In addition to increasing the temperature by ZVI and NZVI induction heating, AC EMF increased intrinsic ZVI and NZVI reactivity, ostensibly due to accelerated corrosion, as demonstrated by the increased ORP. In a soil-water-TCE system, NZVI together with AC EMF thermally enhanced desorption of TCE from soil and increased the degradation of TCE up to 5.36-fold compared to the absence of AC EMF. For the first time, this study indicates the potential for ZVI and NZVI coupled with AC EMF as a combined remediation technique for increasing the rate and completeness of in situ cleanup of adsorbed phase contaminants.

Compound-Specific Isotope Analyses to Assess TCE Biodegradation in a Fractured Dolomitic Aquifer.

PubMed

Clark, Justin A; Stotler, Randy L; Frape, Shaun K; Illman, Walter A

2017-01-01

The potential for trichloroethene (TCE) biodegradation in a fractured dolomite aquifer at a former chemical disposal site in Smithville, Ontario, Canada, is assessed using chemical analysis and TCE and cis-DCE compound-specific isotope analysis of carbon and chlorine collected over a 16-month period. Groundwater redox conditions change from suboxic to much more reducing environments within and around the plume, indicating that oxidation of organic contaminants and degradation products is occurring at the study site. TCE and cis-DCE were observed in 13 of 14 wells sampled. VC, ethene, and/or ethane were also observed in ten wells, indicating that partial/full dechlorination has occurred. Chlorine isotopic values (δ 37 Cl) range between 1.39 to 4.69‰ SMOC for TCE, and 3.57 to 13.86‰ SMOC for cis-DCE. Carbon isotopic values range between -28.9 and -20.7‰ VPDB for TCE, and -26.5 and -11.8‰ VPDB for cis-DCE. In most wells, isotopic values remained steady over the 15-month study. Isotopic enrichment from TCE to cis-DCE varied between 0 and 13‰ for carbon and 1 and 4‰ for chlorine. Calculated chlorine-carbon isotopic enrichment ratios (ϵ Cl /ϵ C ) were 0.18 for TCE and 0.69 for cis-DCE. Combined, isotopic and chemical data indicate very little dechlorination is occurring near the source zone, but suggest bacterially mediated degradation is occurring closer to the edges of the plume. © 2016, National Ground Water Association.

Inhibition of iron (III) minerals and acidification on the reductive dechlorination of trichloroethylene.

PubMed

Paul, Laiby; Smolders, Erik

2014-09-01

Reductive dechlorination of chlorinated ethenes is inhibited by acidification and by the presence of Fe (III) as a competitive electron acceptor. Synergism between both factors on dechlorination is predicted as reductive dissolution of Fe (III) minerals is facilitated by acidification. This study was set-up to assess this synergism for two common aquifer Fe (III) minerals, goethite and ferrihydrite. Anaerobic microbial dechlorination of trichloroethylene (TCE) by KB-1 culture and formate as electron donor was investigated in anaerobic batch containers at different solution pH values (6.2-7.2) in sand coated with these Fe minerals and a sand only as control. In the absence of Fe, lowering substrate pH from 7.2 to 6.2 increased the time for 90% TCE degradation from 14±1d to 42±4d. At pH 7.2, goethite did not affect TCE degradation time while ferrihydrite increased the degradation time to 19±1d compared to the no Fe control. At pH 6.2, 90% degradation was at 78±1 (ferrihydrite) or 131±1d (goethite). Ferrous iron production in ferrihydrite treatment increased between pH 7.2 and 6.5 but decreased by further lowering pH to 6.2, likely due to reduced microbial activity. This study confirms that TCE is increasingly inhibited by the combined effect of acidification and bioavailable Fe (III), however no evidence was found for synergistic inhibition since Fe reduction did not increase as pH decreases. To the best of our knowledge, this is the first study where effect of pH and Fe (III) reduction on TCE was simultaneously tested. Acid Fe-rich aquifers need sufficient buffering and alkalinity to ensure swift degradation of chlorinated ethenes. Copyright © 2014. Published by Elsevier Ltd.

Biodegradation of PCE and TCE in landfill leachate predicted from concentrations of molecular hydrogen: a case study.

PubMed

Gonsoulin, Mary E; Wilson, Barbara H; Wilson, John T

2004-12-01

The Refuse Hideaway Landfill (23-acre) received municipal, commercial, and industrial waste between 1974 and 1988. It was designed as a "natural attenuation" landfill and no provision was made to collect and treat contaminated water. Natural biological degradation through sequential reductive dechlorination had been an important mechanism for natural attenuation at the site. We used the concentration of hydrogen to forecast whether reductive dechlorination would continue over time at particular locations in the plume. Based on published literature, reductive dechlorination and natural attenuation of PCE, TCE, and cis-DCE can be expected in the aquifer if the concentration of molecular hydrogen in monitoring wells are adequate (> 1 nanomolar). Reductive dechlorination can be expected to continue as the ground water moves down gradient. Natural attenuation through reductive dechlorination is not expected in flow paths that originate at down gradient monitoring wells with low concentrations of molecular hydrogen (< 1 nanomolar). In three monitoring wells at the margin of the landfill and in five monitoring wells down gradient of the landfill, ground water maintained a molecular hydrogen concentration, ranging from 1.30 to 9.17 nanomolar, that is adequate for reductive dechlorination. In three of the monitoring wells far down gradient of the landfill, the concentration of molecular hydrogen (0.33 to 0.83 nanomolar) was not adequate to support reductive dechlorination. In wells with adequate concentrations of hydrogen, the concentrations of chlorinated volatile organic compounds were attenuated over time, or concentrations of chlorinated volatile organics were below the detection limit. In wells with inadequate concentrations of hydrogen, the concentrations of chlorinated organic compounds attenuated at a slower rate over time. In wells with adequate hydrogen the first order rate of attenuation of PCE, TCE, cis-DCE and total chlorinated volatile organic compounds varies

MICROBIAL UTILIZATION OF VADOSE ZONE ORGANIC CARBON FOR REDUCTIVE DECHLORINATION OF TETRACHLOROETHENE

EPA Science Inventory

Aqueous extracts from a calcareous spodosol were used as the primary substrate to study the reductive dechlorination of tetrachloroethene (PCE). A comparison was made between extracts obtained using pure water and water saturated with trichloroethene (TCE). The latter solutions w...

A remediation performance model for enhanced metabolic reductive dechlorination of chloroethenes in fractured clay till

NASA Astrophysics Data System (ADS)

Manoli, Gabriele; Chambon, Julie C.; Bjerg, Poul L.; Scheutz, Charlotte; Binning, Philip J.; Broholm, Mette M.

2012-04-01

A numerical model of metabolic reductive dechlorination is used to describe the performance of enhanced bioremediation in fractured clay till. The model is developed to simulate field observations of a full scale bioremediation scheme in a fractured clay till and thereby to assess remediation efficiency and timeframe. A relatively simple approach is used to link the fermentation of the electron donor soybean oil to the sequential dechlorination of trichloroethene (TCE) while considering redox conditions and the heterogeneous clay till system (clay till matrix, fractures and sand stringers). The model is tested on lab batch experiments and applied to describe sediment core samples from a TCE-contaminated site. Model simulations compare favorably to field observations and demonstrate that dechlorination may be limited to narrow bioactive zones in the clay matrix around fractures and sand stringers. Field scale simulations show that the injected donor is expected to be depleted after 5 years, and that without donor re-injection contaminant rebound will occur in the high permeability zones and the mass removal will stall at 18%. Long remediation timeframes, if dechlorination is limited to narrow bioactive zones, and the need for additional donor injections to maintain dechlorination activity may limit the efficiency of ERD in low-permeability media. Future work should address the dynamics of the bioactive zones, which is essential to understand for predictions of long term mass removal.

Radiation induced dechlorination of some chlorinated hydrocarbons in aqueous suspensions of various solid particles

NASA Astrophysics Data System (ADS)

Múčka, V.; Buňata, M.; Čuba, V.; Silber, R.; Juha, L.

2015-07-01

Radiation induced dechlorination of trichloroethylene (TCE) and tetrachloroethylene (PCE) in aqueous solutions containing the active carbon (AC) or cupric oxide (CuO) as the modifiers was studied. The obtained results were compared to the previously studied dechlorination of polychlorinated biphenyls (PCBs). Both modifiers were found to decrease the efficiency of dechlorination. The AC modifier acts mainly via adsorption of the aliphatic (unlike the aromatic) hydrocarbons and the CuO oxide mainly inhibits the mineralization of the perchloroethylene. The results presented in this paper will be also helpful for the studies of the impact of chlorinated hydrocarbons on the membrane permeability of living cells.

Accumulation of dechlorination daughter products: A valid metric of chloroethene biodegradation

USGS Publications Warehouse

Bradley, Paul M.; Chapelle, Frank H.

2007-01-01

In situ reductive dechlorination of perchloroethene (PCE) and trichloroethene (TCE) generates characteristic chlorinated (cis-dichloroethene [cis-DCE] and vinyl chloride [VC]) and nonchlorinated (ethene and ethane) products. The accumulation of these daughter products is commonly used as a metric for ongoing biodegradation at field sites. However, this interpretation assumes that reductive dechlorination is the only chloroethene degradation process of any significance in situ and that the characteristic daughter products of chloroethene reductive dechlorination persist in the environment. Laboratory microcosms, prepared with aquifer and surface-water sediments from hydrologically diverse sites throughout the United States and amended with [1,2-14C] TCE, [1,2-14C] DCE, [1,2-14C] DCA, or [1,2-14C] VC, demonstrated widely variable patterns of intermediate and final product accumulation. In predominantly methanogenic sediment treatments, accumulation of 14C-DCE, 14C-VC, 14C-ethene, and 14C-ethane predominated. Treatments characterized by significant Fe(III) and/or Mn(IV) reduction, on the other hand, demonstrated substantial, and in some cases exclusive, accumulation of 14CO2and 14CH4. These results suggest that relying on the accumulation of cis-DCE, VC, ethene, and ethane may substantially underestimate overall chloroethene biodegradation at many sites.

Potential of isotope analysis (C, Cl) to identify dechlorination mechanisms

NASA Astrophysics Data System (ADS)

Cretnik, Stefan; Thoreson, Kristen; Bernstein, Anat; Ebert, Karin; Buchner, Daniel; Laskov, Christine; Haderlein, Stefan; Shouakar-Stash, Orfan; Kliegman, Sarah; McNeill, Kristopher; Elsner, Martin

2013-04-01

Chloroethenes are commonly used in industrial applications, and detected as carcinogenic contaminants in the environment. Their dehalogenation is of environmental importance in remediation processes. However, a detailed understanding frequently accounted problem is the accumulation of toxic degradation products such as cis-dichloroethylene (cis-DCE) at contaminated sites. Several studies have addressed the reductive dehalogenation reactions using biotic and abiotic model systems, but a crucial question in this context has remained open: Do environmental transformations occur by the same mechanism as in their corresponding in vitro model systems? The presented study shows the potential to close this research gap using the latest developments in compound specific chlorine isotope analysis, which make it possible to routinely measure chlorine isotope fractionation of chloroethenes in environmental samples and complex reaction mixtures.1,2 In particular, such chlorine isotope analysis enables the measurement of isotope fractionation for two elements (i.e., C and Cl) in chloroethenes. When isotope values of both elements are plotted against each other, different slopes reflect different underlying mechanisms and are remarkably insensitive towards masking. Our results suggest that different microbial strains (G. lovleyi strain SZ, D. hafniense Y51) and the isolated cofactor cobalamin employ similar mechanisms of reductive dechlorination of TCE. In contrast, evidence for a different mechanism was obtained with cobaloxime cautioning its use as a model for biodegradation. The study shows the potential of the dual isotope approach as a tool to directly compare transformation mechanisms of environmental scenarios, biotic transformations, and their putative chemical lab scale systems. Furthermore, it serves as an essential reference when using the dual isotope approach to assess the fate of chlorinated compounds in the environment.

Chloroethene dechlorination in acidic groundwater: Implications for combining fenton's treatment with natural attenuation

USGS Publications Warehouse

Bradley, Paul M.; Singletary , Michael A.; Chapelle, Francis H.

2007-01-01

A sulfuric acid leak in 1988 at a chloroethene-contaminated groundwater site at the Naval Air Station Pensacola has resulted in a long-term record of the behavior of chloroethene contaminants at low pH and a unique opportunity to assess the potential impact of source area treatment technologies, which involve acidification of the groundwater environment (e.g., Fenton's-based in situ chemical oxidation), on downgradient natural attenuation processes. The greater than 75 percent decrease in trichloroethene (TCE) concentrations and the shift in contaminant composition toward predominantly reduced daughter products (dichloroethene [DCE] and vinyl chloride [VC]) that were observed along a 30-m groundwater flow path characterized by highly acidic conditions (pH = 3.5 ± 0.4) demonstrated that chloroethene reductive dechlorination can continue to be efficient under persistent acidic conditions. The detection of Dehalococcoides-type bacteria within the sulfuric acid/chloroethene co-contaminant plume was consistent with biotic chloroethene reductive dechlorination. Microcosm studies conducted with 14C-TCE and 14C-VC confirmed biotic reductive dechlorination in sediment collected from within the sulfuric acid/chloroethene co-contaminant plume. Microcosms prepared with sediment from two other locations within the acid plume, however, demonstrated only a limited mineralization to 14CO2 and 14CO, which was attributed to abiotic degradation because no significant differences were observed between experimental and autoclaved control treatments. These results indicated that biotic and abiotic mechanisms contributed to chloroethene attenuation in the acid plume at NAS Pensacola and that remediation techniques involving acidification of the groundwater environment (e.g., Fenton's-based source area treatment) do not necessarily preclude efficient chloroethene degradation.

Abiotic dechlorination of chlorinated ethenes in natural clayey soils: Impacts of mineralogy and temperature

NASA Astrophysics Data System (ADS)

Schaefer, Charles E.; Ho, Paul; Gurr, Christopher; Berns, Erin; Werth, Charles

2017-11-01

Laboratory batch experiments were performed to assess the impacts of temperature and mineralogy on the abiotic dechlorination of tetrachloroethene (PCE) or trichloroethene (TCE) due to the presence of ferrous minerals in natural aquifer clayey soils under anaerobic conditions. A combination of x-ray diffraction (XRD), magnetic susceptibility, and ferrous mineral content were used to characterize each of the 3 natural soils tested in this study, and dechlorination at temperatures ranging from 20 to 55 °C were examined. Results showed that abiotic dechlorination occurred in all 3 soils examined, yielding reduced gas abiotic dechlorination products acetylene, butane, ethene, and/or propane. Bulk first-order dechlorination rate constants (kbulk), scaled to the soil:water ratio expected for in situ conditions, ranged from 2.0 × 10- 5 day- 1 at 20 °C, to 32 × 10- 5 day- 1 at 55 °C in the soil with the greatest ferrous mineral content. For the generation of acetylene and ethene from PCE, the reaction was well described by Arrhenius kinetics, with an activation energy of 91 kJ/mol. For the generation of coupling products butane and propane, the Arrhenius equation did not provide a satisfactory description of the data, likely owing to the complex reaction mechanisms associated with these products and/or diffusional mass transfer processes associated with the ferrous minerals likely responsible for these coupling reactions. Although the data set was too limited to determine a definitive correlation, the two soils with elevated ferrous mineral contents had elevated abiotic dechlorination rate constants, while the one soil with a low ferrous mineral content had a relatively low abiotic dechlorination rate constant. Overall, results suggest intrinsic abiotic dechlorination rates may be an important long-term natural attenuation component in site conceptual models for clays that have the appropriate iron mineralogy.

Further biogeochemical characterization of a trichloroethene-contaminated fractured dolomite aquifer: Electron source and microbial communities involved in reductive dechlorination

USGS Publications Warehouse

Hohnstock-Ashe, A. M.; Plummer, S.M.; Yager, R.M.; Baveye, P.; Madsen, E.L.

2001-01-01

A recent article presented geochemical and microbial evidence establishing metabolic adaptation to and in-situ reductive dechlorination of trichloroethene (TCE) in a fractured dolomite aquifer. This study was designed to further explore site conditions and microbial populations and to explain previously reported enhancement of reductive dechlorination by the addition of pulverized dolomite to laboratory microcosms. A survey of groundwater geochemical parameters (chlorinated ethenes, ethene, H2, CH4, DIC, DOC, and ??13C values for CH4, DIC, and DOC) indicated that in situ reductive dechlorination was ongoing and that an unidentified pool of organic carbon was contributing, likely via microbial respiration, to the large and relatively light onsite DIC pool. Petroleum hydrocarbons associated with the dolomite rock were analyzed by GC/MS and featured a characteristically low ??13C value. Straight chain hydrocarbons were extracted from the dolomite previously found to stimulate reductive dechlorination; these were particularly depleted in hexadecane (HD). Thus, we hypothesized that HD and related hydrocarbons might be anaerobically respired and serve both as the source of onsite DIC and support reductive dechlorination of TCE. Microcosms amended with pulverized dolomite demonstrated reductive dechlorination, whereas a combusted dolomite amendment did not. HD-amended microcosms were also inactive. Therefore, the stimulatory factor in the pulverized dolomite was heat labile, but that component was not HD. Amplified Ribosomal DNA Restriction Analysis (ARDRA) of the microbial populations in well waters indicated that a relatively low diversity, sulfur-transforming community outside the plume was shifted toward a high diversity community including Dehalococcoides ethenogenes-type microorganisms inside the zone of contamination. These observations illustrate biogeochemical intricacies of in situ reductive dechlorination reactions.

Chlorine isotope effects from isotope ratio mass spectrometry suggest intramolecular C-Cl bond competition in trichloroethene (TCE) reductive dehalogenation.

PubMed

Cretnik, Stefan; Bernstein, Anat; Shouakar-Stash, Orfan; Löffler, Frank; Elsner, Martin

2014-05-20

Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (bio)chemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE) dehalogenation was investigated. Selective biotransformation reactions (i) of tetrachloroethene (PCE) to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii) of TCE to cis-1,2-dichloroethene (cis-DCE) in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were -19.0‰ ± 0.9‰ (PCE) and -12.2‰ ± 1.0‰ (TCE) (95% confidence intervals). Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (-5.0‰ ± 0.1‰) and TCE (-3.6‰ ± 0.2‰). In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by -16.3‰ ± 1.4‰ (standard error)) than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of -2.4‰ ± 0.3‰ and the product chloride an isotope effect of -6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals). A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect). These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition). This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I) or single electron transfer as reductive dehalogenation mechanisms.

[Preparation of Coated CMC-Fe0 Using Rheological Phase Reaction Method and Research on Degradation of TCE in Water].

PubMed

Fan, Wen-jing; Cheng, Yue; Yu, Shu-zhen; Fan, Xiao-feng

2015-06-01

The coated nanoscale zero-valent iron (coated CMC-Fe0) was synthesized with cheap and environment friendly CMC as the coating agent using rheological phase reaction. The sample was characterized by means of XRD, SEM, TEM and N2 adsorption-stripping and used to study reductive dechlorination of TCE. The experimental results indicated that the removal rate of TCE was about 100% when the CMC-Fe0 dosage was 6 g x L(-1), the initial TCE concentration was 5 mg x L(-1) and the reaction time was 40 h. The TCE degradation reaction of coated CMC-Fe0 followed a pseudo-first-order kinetic model. Finally, the product could be simply recovered.

Treatment of co-mingled benzene, toluene and TCE in groundwater.

PubMed

Chen, Liang; Liu, Yulong; Liu, Fei; Jin, Song

2014-06-30

This work addressed a hypothetical but practical scenario that includes biological oxidation and reductive dechlorination in treating groundwater containing co-mingled plume of trichloroethene (TCE), benzene and toluene. Groundwater immediately downgradient from the commonly used zero-valent iron (ZVI) has shown alkaline pH (up to 10.7). The elevated pH may influence BTEX compounds (i.e., benzene, toluene, ethyl benzene, and xylenes) biodegradation, which could also be inhibited by elevated concentrations of TCE. Data from this work suggests that the inhibition coefficients (IC) value for 100 μg/L and 500 μg/L of TCE on benzene and toluene degradation are 2.1-2.8 at pH 7.9, and 3.5-6.1 at pH 10.5. For a co-mingled plume, it appears to be more effective to reduce TCE by ZVI before addressing benzene and toluene biodegradation. The ample buffering capacity of most groundwater and the adaptation of benzene and toluene-degrading microbes are likely able to eliminate the adverse influence of pH shifts downgradient from a ZVI-PRB. Copyright © 2014 Elsevier B.V. All rights reserved.

Ground water chlorinated ethenes in tree trunks: Case studies, influence of recharge, and potential degradation mechanism

USGS Publications Warehouse

Vroblesky, D.A.; Clinton, B.D.; Vose, J.M.; Casey, C.C.; Harvey, G.J.; Bradley, P.M.

2004-01-01

Trichloroethene (TCE) was detected in cores of trees growing above TCE-contaminated ground at three sites: the Carswell Golf Course in Texas, Air Force Plant PJKS in Colorado, and Naval Weapons Station Charleston in South Carolina. This was true even when the depth to water was 7.9 m or when the contaminated aquifer was confined beneath ???3 m of clay. Additional ground water contaminants detected in the tree cores were cis-1,2-dichloroethene at two sites and tetrachloroethene at one site. Thus, tree coring can be a rapid and effective means of locating shallow subsurface chlorinated ethenes and possibly identifying zones of active TCE dechlorination. Tree cores collected over time were useful in identifying the onset of ground water contamination. Several factors affecting chlorinated ethene concentrations in tree cores were identified in this investigation. The factors include ground water chlorinated ethene concentrations and depth to ground water contamination. In addition, differing TCE concentrations around the trunk of some trees appear to be related to the roots deriving water from differing areas. Opportunistic uptake of infiltrating rainfall can dilute prerain TCE concentrations in the trunk. TCE concentrations in core headspace may differ among some tree species. In some trees, infestation of bacteria in decaying heartwood may provide a TCE dechlorination mechanism within the trunk.

Parameter Sensitivity and Laboratory Benchmarking of a Biogeochemical Process Model for Enhanced Anaerobic Dechlorination

NASA Astrophysics Data System (ADS)

Kouznetsova, I.; Gerhard, J. I.; Mao, X.; Barry, D. A.; Robinson, C.; Brovelli, A.; Harkness, M.; Fisher, A.; Mack, E. E.; Payne, J. A.; Dworatzek, S.; Roberts, J.

2008-12-01

A detailed model to simulate trichloroethene (TCE) dechlorination in anaerobic groundwater systems has been developed and implemented through PHAST, a robust and flexible geochemical modeling platform. The approach is comprehensive but retains flexibility such that models of varying complexity can be used to simulate TCE biodegradation in the vicinity of nonaqueous phase liquid (NAPL) source zones. The complete model considers a full suite of biological (e.g., dechlorination, fermentation, sulfate and iron reduction, electron donor competition, toxic inhibition, pH inhibition), physical (e.g., flow and mass transfer) and geochemical processes (e.g., pH modulation, gas formation, mineral interactions). Example simulations with the model demonstrated that the feedback between biological, physical, and geochemical processes is critical. Successful simulation of a thirty-two-month column experiment with site soil, complex groundwater chemistry, and exhibiting both anaerobic dechlorination and endogenous respiration, provided confidence in the modeling approach. A comprehensive suite of batch simulations was then conducted to estimate the sensitivity of predicted TCE degradation to the 36 model input parameters. A local sensitivity analysis was first employed to rank the importance of parameters, revealing that 5 parameters consistently dominated model predictions across a range of performance metrics. A global sensitivity analysis was then performed to evaluate the influence of a variety of full parameter data sets available in the literature. The modeling study was performed as part of the SABRE (Source Area BioREmediation) project, a public/private consortium whose charter is to determine if enhanced anaerobic bioremediation can result in effective and quantifiable treatment of chlorinated solvent DNAPL source areas. The modelling conducted has provided valuable insight into the complex interactions between processes in the evolving biogeochemical systems

Stable carbon isotope fractionation of chlorinated ethenes by a microbial consortium containing multiple dechlorinating genes.

PubMed

Liu, Na; Ding, Longzhen; Li, Haijun; Zhang, Pengpeng; Zheng, Jixing; Weng, Chih-Huang

2018-08-01

The study aimed to determine the possible contribution of specific growth conditions and community structures to variable carbon enrichment factors (Ɛ- carbon ) values for the degradation of chlorinated ethenes (CEs) by a bacterial consortium with multiple dechlorinating genes. Ɛ- carbon values for trichloroethylene, cis-1,2-dichloroethylene, and vinyl chloride were -7.24% ± 0.59%, -14.6% ± 1.71%, and -21.1% ± 1.14%, respectively, during their degradation by a microbial consortium containing multiple dechlorinating genes including tceA and vcrA. The Ɛ- carbon values of all CEs were not greatly affected by changes in growth conditions and community structures, which directly or indirectly affected reductive dechlorination of CEs by this consortium. Stability analysis provided evidence that the presence of multiple dechlorinating genes within a microbial consortium had little effect on carbon isotope fractionation, as long as the genes have definite, non-overlapping functions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Phreatophyte influence on reductive dechlorination in a shallow aquifer contaminated with trichloroethene (TCE)

USGS Publications Warehouse

Lee, R.W.; Jones, S.A.; Kuniansky, E.L.; Harvey, G.; Lollar, B.S.; Slater, G.F.

2000-01-01

Phytoremediation uses the natural ability of plants to degrade contaminants in groundwater. A field demonstration designed to remediate aerobic shallow groundwater contaminated with trichloroethene began in April 1996 with the planting of cottonwood trees, a short-rotation woody crop, over an approximately 0.2-ha area at the Naval Air Station, Fort Worth, Texas. The project was developed to demonstrate capture of contaminated groundwater and degradation of contaminants by phreatophytes. Analyses from samples of groundwater collected from July 1997 to June 1998 indicate that tree roots have the potential to create anaerobic conditions in the groundwater that will facilitate degradation of trichloroethene by microbially mediated reductive dechlorination. Organic matter from root exudates and decay of tree roots probably stimulate microbial activity, consuming dissolved oxygen. Dissolved oxygen concentrations, which varied across the site, were smallest near a mature cottonwood tree (about 20 years of age and 60 meters southwest of the cottonwood plantings) where degradation products of trichloroethene were measured. Oxidation of organic matter is the primary microbially mediated reaction occurring in the groundwater beneath the planted trees whereas near the mature cottonwood tree, data indicate that methanogenesis is the most probable reaction occurring. Reductive dechlorination in groundwater either is not occurring or is not a primary process away from the mature tree. Carbon-13 isotope values for trichloroethene are nearly identical at locations away from the mature tree, further confirming that dechlorination is not occurring at the site.

In situ redox manipulation of subsurface sediments from Fort Lewis, Washington: Iron reduction and TCE dechlorination mechanisms

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

JE Szecsody; JS Fruchter; DS Sklarew

2000-03-21

Pacific Northwest National Laboratory (PNNL) conducted a bench-scale study to determine how effective chemically treated Ft. Lewis sediments can degrade trichloroethylene (TCE). The objectives of this experimental study were to quantify: (1) sediment reduction and oxidation reactions, (2) TCE degradation reactions, and (3) other significant geochemical changes that occurred. Sediment reduction and oxidation were investigated to determine the mass of reducible iron in the Ft. Lewis sediments and the rate of this reduction and subsequent oxidation at different temperatures. The temperature dependence was needed to be able to predict field-scale reduction in the relatively cold ({approximately}11 C) Ft. Lewis aquifer.more » Results of these experiments were used in conjunction with other geochemical and hydraulic characterization to design the field-scale injection experiment and predict barrier longevity. For example, the sediment reduction rate controls the amount of time required for the dithionite solution to fully react with sediments. Sediment oxidation experiments were additionally conducted to determine the oxidation rate and provide a separate measure of the mass of reduced iron. Laboratory experiments that were used to meet these objectives included: (1) sediment reduction in batch (static) systems, (2) sediment reduction in 1-D columns, and (3) sediment oxidation in 1-D columns. Multiple reaction modeling was conducted to quantify the reactant masses and reaction rates.« less

A CuNi bimetallic cathode with nanostructured copper array for enhanced hydrodechlorination of trichloroethylene (TCE).

PubMed

Liu, Bo; Zhang, Hao; Lu, Qi; Li, Guanghe; Zhang, Fang

2018-09-01

To address the challenges of low hydrodechlorination efficiency by non-noble metals, a CuNi bimetallic cathode with nanostructured copper array film was fabricated for effective electrochemical dechlorination of trichloroethylene (TCE) in aqueous solution. The CuNi bimetallic cathodes were prepared by a simple one-step electrodeposition of copper onto the Ni foam substrate, with various electrodeposition time of 5/10/15/20 min. The optimum electrodeposition time was 10 min when copper was coated as a uniform nanosheet array on the nickel foam substrate surface. This cathode exhibited the highest TCE removal, which was twice higher compared to that of the nickel foam cathode. At the same passed charge of 1080C, TCE removal increased from 33.9 ± 3.3% to 99.7 ± 0.1% with the increasing operation current from 5 to 20 mA cm -2 , while the normalized energy consumption decreased from 15.1 ± 1.0 to 2.6 ± 0.01 kWh log -1  m -3 . The decreased normalized energy consumption at a higher current density was due to the much higher removal efficiency at a higher current. These results suggest that CuNi cathodes prepared by simple electrodeposition method represent a promising and cost-effective approach for enhanced electrochemical dechlorination. Copyright © 2018 Elsevier B.V. All rights reserved.

Kinetic Mechanism of the Dechlorinating Flavin-dependent Monooxygenase HadA*

PubMed Central

Pimviriyakul, Panu; Thotsaporn, Kittisak; Sucharitakul, Jeerus; Chaiyen, Pimchai

2017-01-01

The accumulation of chlorophenols (CPs) in the environment, due to their wide use as agrochemicals, has become a serious environmental problem. These organic halides can be degraded by aerobic microorganisms, where the initial steps of various biodegradation pathways include an oxidative dechlorinating process in which chloride is replaced by a hydroxyl substituent. Harnessing these dechlorinating processes could provide an opportunity for environmental remediation, but detailed catalytic mechanisms for these enzymes are not yet known. To close this gap, we now report transient kinetics and product analysis of the dechlorinating flavin-dependent monooxygenase, HadA, from the aerobic organism Ralstonia pickettii DTP0602, identifying several mechanistic properties that differ from other enzymes in the same class. We first overexpressed and purified HadA to homogeneity. Analyses of the products from single and multiple turnover reactions demonstrated that HadA prefers 4-CP and 2-CP over CPs with multiple substituents. Stopped-flow and rapid-quench flow experiments of HadA with 4-CP show the involvement of specific intermediates (C4a-hydroperoxy-FAD and C4a-hydroxy-FAD) in the reaction, define rate constants and the order of substrate binding, and demonstrate that the hydroxylation step occurs prior to chloride elimination. The data also identify the non-productive and productive paths of the HadA reactions and demonstrate that product formation is the rate-limiting step. This is the first elucidation of the kinetic mechanism of a two-component flavin-dependent monooxygenase that can catalyze oxidative dechlorination of various CPs, and as such it will serve as the basis for future investigation of enzyme variants that will be useful for applications in detoxifying chemicals hazardous to human health. PMID:28159841

Comparison of dechlorination rates for field DNAPL vs synthetic samples: effect of sample matrix

NASA Astrophysics Data System (ADS)

O'Carroll, D. M.; Sakulchaicharoen, N.; Herrera, J. E.

2015-12-01

Nanometals have received significant attention in recent years due to their ability to rapidly destroy numerous priority source zone contaminants in controlled laboratory studies. This has led to great optimism surrounding nanometal particle injection for insitu remediation. Reported dechlorination rates vary widely among different investigators. These differences have been ascribed to differences in the iron types (granular, micro, or nano-sized iron), matrix solution chemistry and the morphology of the nZVI surface. Among these, the effects of solution chemistry on rates of reductive dechlorination of various chlorinated compounds have been investigated in several short-term laboratory studies. Variables investigated include the effect of anions or groundwater solutes such as SO4-2, Cl-, NO3-, pH, natural organic matters (NOM), surfactant, and humic acid on dechlorination reaction of various chlorinated compounds such as TCE, carbon tetrachloride (CT), and chloroform (CF). These studies have normally centered on the assessment of nZVI reactivity toward dechlorination of an isolated individual contaminant spiked into a ground water sample under ideal conditions, with limited work conducted using real field samples. In this work, the DNAPL used for the dechlorination study was obtained from a contaminatied site. This approach was selected to adequately simulate a condition where the nZVI suspension was in direct contact with DNAPL and to isolate the dechlorination activity shown by the nZVI from the groundwater matrix effects. An ideal system "synthetic DNAPL" composed of a mixture of chlorinated compounds mimicking the composition of the actual DNAPL was also dechlorinated to evaluate the DNAPL "matrix effect" on NZVI dechlorination activity. This approach allowed us to evaluate the effect of the presence of different types of organic compounds (volatile fatty acids and humic acids) found in the actual DNAPL on nZVI dechlorination activity. This presentation will

Adsorbed poly(aspartate) coating limits the adverse effects of dissolved groundwater solutes on Fe0 nanoparticle reactivity with trichloroethylene.

PubMed

Phenrat, Tanapon; Schoenfelder, Daniel; Kirschling, Teresa L; Tilton, Robert D; Lowry, Gregory V

2018-03-01

For in situ groundwater remediation, polyelectrolyte-modified nanoscale zerovalent iron particles (NZVIs) have to be delivered into the subsurface, where they degrade pollutants such as trichloroethylene (TCE). The effect of groundwater organic and ionic solutes on TCE dechlorination using polyelectrolyte-modified NZVIs is unexplored, but is required for an effective remediation design. This study evaluates the TCE dechlorination rate and reaction by-products using poly(aspartate) (PAP)-modified and bare NZVIs in groundwater samples from actual TCE-contaminated sites in Florida, South Carolina, and Michigan. The effects of groundwater solutes on short- and intermediate-term dechlorination rates were evaluated. An adsorbed PAP layer on the NZVIs appeared to limit the adverse effect of groundwater solutes on the TCE dechlorination rate in the first TCE dechlorination cycle (short-term effect). Presumably, the pre-adsorption of PAP "trains" and the Donnan potential in the adsorbed PAP layer prevented groundwater solutes from further blocking NZVI reactive sites, which appeared to substantially decrease the TCE dechlorination rate of bare NZVIs. In the second and third TCE dechlorination cycles (intermediate-term effect), TCE dechlorination rates using PAP-modified NZVIs increased substantially (~100 and 200%, respectively, from the rate of the first spike). The desorption of PAP from the surface of NZVIs over time due to salt-induced desorption is hypothesized to restore NZVI reactivity with TCE. This study suggests that NZVI surface modification with small, charged macromolecules, such as PAP, helps to restore NZVI reactivity due to gradual PAP desorption in groundwater.

Promising Emerging Mechanisms

EPA Science Inventory

Most applications of enhanced in situ bioremediation are based on biological reductive dechlorination. Anaerobic metabolism can also produce reactive minerals that allow for in situ biogeochemical transformation of chlorinated organic contaminants such as PCE, TCE, and cis-DCE. ...

Green remediation: enhanced reductive dechlorination using recycled rinse water as bioremediation substrate

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

Dawson, Gaynor; McKeon, Tom

Enhanced reductive dechlorination (ERD) has rapidly become a remedy of choice for use on chlorinated solvent contamination when site conditions allow. With this approach, solutions of an organic substrate are injected into the affected aquifer to stimulate biological growth and the resultant production of reducing conditions in the target zone. Under the reducing conditions, hydrogen is produced and ultimately replaces chlorine atoms on the contaminant molecule causing sequential dechlorination. Under suitable conditions the process continues until the parent hydrocarbon precursor is produced, such as the complete dechlorination of trichloroethylene (TCE) to ethene. The process is optimized by use of amore » substrate that maximizes hydrogen production per unit cost. When natural biota are not present to promote the desired degradation, inoculates can be added with the substrate. The in-situ method both reduces cost and accelerates cleanup. Successful applications have been extended from the most common chlorinated compounds perchloroethylene (PCE) and TCE and related products of degradation, to perchlorate, and even explosives such as RDX and trinitrotoluene on which nitrates are attacked in lieu of chloride. In recent work, the process has been further improved through use of beverage industry wastewaters that are available at little or no cost. With material cost removed from the equation, applications can maximize the substrate loading without significantly increasing total cost. The extra substrate loading both accelerates reaction rates and extends the period of time over which reducing conditions are maintained. In some cases, the presence of other organic matter in addition to simple sugars provides for longer performance times of individual injections, thereby working in a fashion similar to emulsified vegetable oil. The paper discusses results of applications at three different sites contaminated with chlorinated ethylenes. The applications have

Monitoring TCE Degradation by In-situ Bioremediation in TCE-Contaminated site

NASA Astrophysics Data System (ADS)

Han, K.; Hong, U.; Ahn, G.; Jiang, H.; Yoo, H.; Park, S.; Kim, N.; Ahn, H.; Kwon, S.; Kim, Y.

2012-12-01

Trichloroethylene (TCE) is a long-term common groundwater pollutant because the compound with high density is slowly released into groundwater. Physical and chemical remediation processes have been used to clean-up the contaminant, but novel remediation technology is required to overcome a low efficiency of the traditional treatment process. Many researchers focused on biological process using an anaerobic TCE degrading culture, but it still needs to evaluate whether the process can be applied into field scale under aerobic condition. Therefore, in this work we investigated two different tests (i.e., biostimulation and bioaugmentation) of biological remediation through the Well-to-Well test (injection well to extraction well) in TCE-contaminated site. Also solutions (Electron donor & acceptor, tracer) were injected into the aquifer using a liquid coupled with nitrogen gas sparging. In biostimulation, we use 3 phases to monitoring biological remediation. Phase 1: we inject formate solution to get electron donor hydrogen (hydrogen can be generated from fermentation of formate). We also inject bromide as tracer. Phase 2: we made injection solution by formate, bromide and sulfate. The reason why we inject sulfate is that as a kind of electron accepter, sulfate reduction process is helpful to create anaerobic condition. Phase 3: we inject mixed solution made by formate, sulfate, fumarate, and bromide. The degradation of fumarate has the same mechanism and condition with TCE degradation, so we added fumarate to make sure that if the anaerobic TCE degradation by indigenous microorganisms started up (Because low TCE concentration by gas sparging). In the bioaugmentation test, we inject the Evanite culture (containing dehalococcoides spp) and TCE degradation to c-DCE, VC, ETH was monitored. We are evaluating the transport of the Evanite culture in the field by measuring TCE and VC reductases.

Reactive Minerals and Dechlorinating Communities: Mechanisms Governing the Degradation of Chlorinated Ethenes during Back Diffusion from Low Permeability Zones in Aerobic and Anaerobic Environments

NASA Astrophysics Data System (ADS)

Berns, E. C.; Zeng, R.; Singh, H.; Valocchi, A. J.; Sanford, R. A.; Strathmann, T. J.; Schaefer, C. E.; Werth, C. J.

2017-12-01

Low permeability zones (LPZs) comprised of silts and clays, and contaminated with chlorinated ethenes, can act as a long term source of contaminated groundwater by diffusion into adjacent high permeability zones (HPZs). Following initial remediation efforts, chlorinated ethenes that have diffused into LPZs will back diffuse and recontaminate HPZs. Because chlorinated ethenes are known to cause cancer and damage the liver, kidneys, and central nervous system, it is important to understand how they degrade in natural systems and how to model their fate and transport. Previous work has shown that anaerobic hydrogenolysis reactions are facilitated by both dechlorinating microorganisms and reactive minerals. Abiotic dichloro-elimination reactions with reactive minerals can also degrade chlorinated ethenes to acetylene, albeit at slower rates than biotic processes. More recently, studies have explored aerobic abiotic degradation of chlorinated ethenes to formate, glycolate, and carbon dioxide. This study focuses on these biotic and abiotic reactions and their contributions to chlorinated ethene degradation under aerobic and anaerobic conditions at the LPZ/HPZ interface. A two-dimensional flow cell was constructed to model this interface using clay and sand from Pease Air Force Base. The clay was inoculated with a dechlorinating enrichment culture. Tenax adsorbent beads equilibrated with trichloroethylene (TCE) were used as a chlorinated ethene source zone at the base of the clay. TCE and its degradation products diffused from the clay into the sand, where they were removed from the flow cell by groundwater at a rate of 50 mL/day. Volatile compounds were trapped in a sample loop and removed every 48 hours for analysis by GC-FID. Organic and inorganic ions in the effluent were analyzed on the HPLC and IC. The experiment was terminated by freezing the flow cell, and chemical profiles through the flow cell material were created to show the spatial distribution of degradation

Stable Carbon Isotope Evidence and Quantification of Reductive Dechlorination of Chlorinated Ethenes at Kelly AFB, TX

NASA Astrophysics Data System (ADS)

Morrill, P.; Lacrampe-Couloume, G.; Slater, G.; Sleep, B.; Edwards, E.; McMaster, M.; Major, D.; Sherwood Lollar, B.

2002-12-01

Cis-1, 2-dichloroethene (cDCE) was the primary volatile organic compound (VOC) after biostimulation of a perchloroethene (PCE) plume in a pilot test at Kelly Air Force Base (AFB) in San Antonio Texas. A stable natural microbial consortium, KB-1, shown in laboratory experiments to reduce chlorinated ethenes to non-toxic ethene was added in a pilot test area (PTA). After the addition of KB-1 stable carbon isotope values were measured for each chlorinated ethene to verify the occurrence of reductive dechlorination and quantify the extent of cDCE degradation. After bioaugmentation with KB-1, PCE, TCE and cDCE concentrations declined, while VC concentrations increased and subsequently decreased, as ethene became the dominant transformation product measured. Shifts in carbon isotopic values up to 2.7 permil, 6.4 permil, 10.9 permil and 10.6 permil were observed for PCE, TCE, cDCE and VC respectively. These isotopic shifts are consistent with the effects of biodegradation observed during laboratory and field studies. Most notably, isotopic enrichment trends characteristic of reductive dechlorination were detectable in the parent compounds before measurable concentrations of daughter products VC and ethene were produced. These results illustrate the advantage of using the more sensitive compound specific isotope analysis to confirm degradation in addition to the traditional method of monitoring the appearance of degradation products. Fractionation factors obtained from laboratory studies were used in conjunction with isotope data measured in the field to estimate the extent of cDCE degraded. It is estimated that within a 44 day period, 37 to 48 percent of the cDCE was reductively dechlorinated. Independent biodegradation estimates using data from a bromide tracer test, a groundwater flow model, and concentration analyses were all in good agreement with the isotope degradation estimate.

DFN-M field characterization of sandstone for a process-based site conceptual model and numerical simulations of TCE transport with degradation

NASA Astrophysics Data System (ADS)

Pierce, Amanda A.; Chapman, Steven W.; Zimmerman, Laura K.; Hurley, Jennifer C.; Aravena, Ramon; Cherry, John A.; Parker, Beth L.

2018-05-01

Plumes of trichloroethene (TCE) with degradation products occur at a large industrial site in California where TCE as a dense non-aqueous phase liquid (DNAPL) entered the fractured sandstone bedrock at many locations beginning in the late 1940s. Groundwater flows rapidly in closely spaced fractures but plume fronts are strongly retarded relative to groundwater flow velocities owing largely to matrix diffusion in early decades and degradation processes in later decades and going forward. Multiple data types show field evidence for both biotic and abiotic dechlorination of TCE and its degradation products, resulting in non-chlorinated compounds. Analyses were conducted on groundwater samples from hundreds of monitoring wells and on thousands of rock samples from continuous core over depths ranging from 6 to 426 metres below ground surface. Nearly all of the present-day mass of TCE and degradation products resides in the water-saturated, low-permeability rock matrix blocks. Although groundwater and DNAPL flow primarily occur in the fractures, DNAPL dissolution followed by diffusion and sorption readily transfers contaminant mass into the rock matrix. The presence of non-chlorinated degradation products (ethene, ethane, acetylene) and compound specific isotope analysis (CSIA) of TCE and cis-1,2-dichloroethene (cDCE) indicate at least some complete dechlorination by both biotic and abiotic pathways, consistent with the observed mineralogy and hydrogeochemistry and with published results from crushed rock microcosms. The rock matrix contains abundant iron-bearing minerals and solid-phase organic carbon with large surface areas and long contact times, suggesting degradation processes are occurring in the rock matrix. Multiple, high-resolution datasets provide strong evidence for spatially heterogeneous distributions of TCE and degradation products with varying degrees of degradation observed only when using new methods that achieve better detection of dissolved gases (i

DFN-M field characterization of sandstone for a process-based site conceptual model and numerical simulations of TCE transport with degradation.

PubMed

Pierce, Amanda A; Chapman, Steven W; Zimmerman, Laura K; Hurley, Jennifer C; Aravena, Ramon; Cherry, John A; Parker, Beth L

2018-05-01

Plumes of trichloroethene (TCE) with degradation products occur at a large industrial site in California where TCE as a dense non-aqueous phase liquid (DNAPL) entered the fractured sandstone bedrock at many locations beginning in the late 1940s. Groundwater flows rapidly in closely spaced fractures but plume fronts are strongly retarded relative to groundwater flow velocities owing largely to matrix diffusion in early decades and degradation processes in later decades and going forward. Multiple data types show field evidence for both biotic and abiotic dechlorination of TCE and its degradation products, resulting in non-chlorinated compounds. Analyses were conducted on groundwater samples from hundreds of monitoring wells and on thousands of rock samples from continuous core over depths ranging from 6 to 426 metres below ground surface. Nearly all of the present-day mass of TCE and degradation products resides in the water-saturated, low-permeability rock matrix blocks. Although groundwater and DNAPL flow primarily occur in the fractures, DNAPL dissolution followed by diffusion and sorption readily transfers contaminant mass into the rock matrix. The presence of non-chlorinated degradation products (ethene, ethane, acetylene) and compound specific isotope analysis (CSIA) of TCE and cis-1,2-dichloroethene (cDCE) indicate at least some complete dechlorination by both biotic and abiotic pathways, consistent with the observed mineralogy and hydrogeochemistry and with published results from crushed rock microcosms. The rock matrix contains abundant iron-bearing minerals and solid-phase organic carbon with large surface areas and long contact times, suggesting degradation processes are occurring in the rock matrix. Multiple, high-resolution datasets provide strong evidence for spatially heterogeneous distributions of TCE and degradation products with varying degrees of degradation observed only when using new methods that achieve better detection of dissolved gases (i

Determination of rate constants and branching ratios for TCE degradation by zero-valent iron using a chain decay multispecies model.

PubMed

Hwang, Hyoun-Tae; Jeen, Sung-Wook; Sudicky, Edward A; Illman, Walter A

2015-01-01

The applicability of a newly-developed chain-decay multispecies model (CMM) was validated by obtaining kinetic rate constants and branching ratios along the reaction pathways of trichloroethene (TCE) reduction by zero-valent iron (ZVI) from column experiments. Changes in rate constants and branching ratios for individual reactions for degradation products over time for two columns under different geochemical conditions were examined to provide ranges of those parameters expected over the long-term. As compared to the column receiving deionized water, the column receiving dissolved CaCO3 showed higher mean degradation rates for TCE and all of its degradation products. However, the column experienced faster reactivity loss toward TCE degradation due to precipitation of secondary carbonate minerals, as indicated by a higher value for the ratio of maximum to minimum TCE degradation rate observed over time. From the calculated branching ratios, it was found that TCE and cis-dichloroethene (cis-DCE) were dominantly dechlorinated to chloroacetylene and acetylene, respectively, through reductive elimination for both columns. The CMM model, validated by the column test data in this study, provides a convenient tool to determine simultaneously the critical design parameters for permeable reactive barriers and natural attenuation such as rate constants and branching ratios. Copyright © 2015 Elsevier B.V. All rights reserved.

Characterization of a microbial consortium capable of rapid and simultaneous dechlorination of 1,1,2,2-tetrachloroethane and chlorinated ethane and ethene intermediates

USGS Publications Warehouse

Jones, E.J.P.; Voytek, M.A.; Lorah, M.M.; Kirshtein, J.D.

2006-01-01

A study was carried out to develop a culture of microorganisms for bioaugmentation treatment of chlorinated-ethane contaminated groundwater at sites where dechlorination is incomplete or rates are too slow for effective remedation. Mixed cultures capable of dechlorinating chlorinated ethanes and ethenes were enriched from contaminated wetland sediment at Aberdeen Proving Ground (APG) Maryland. The West Branch Consortium (WBC-2) was capable of degrading 1,1,2,2-tetrachloroethane (TeCA), trichloroethylene (TCE), cis and trans 1,2-dichloroethylene (DCE), 1,1,2-trichloroethane (TCA), 1,2-dichloroethane, and vinyl chloride to nonchlorinated end products ethylene and ethane. WBC-2 dechlorinated TeCA, TCA, and cisDCE rapidly and simultaneously. Methanogens in the consortium were members of the class Methanomicrobia, which includes acetoclastic methanogens. The WBC-2 consortium provides opportunities for the in situ bioremediation of sites contaminated with mixtures of chlorinated ethylenes and ethanes.

Molecular Characterization of a Dechlorinating Community Resulting from In Situ Biostimulation in a Trichloroethene-Contaminated Deep, Fractured Basalt Aquifer and Comparison to a Derivative Laboratory Culture

PubMed Central

Macbeth, Tamzen W.; Cummings, David E.; Spring, Stefan; Petzke, Lynn M.; Sorenson, Kent S.

2004-01-01

Sodium lactate additions to a trichloroethene (TCE) residual source area in deep, fractured basalt at a U.S. Department of Energy site have resulted in the enrichment of the indigenous microbial community, the complete dechlorination of nearly all aqueous-phase TCE to ethene, and the continued depletion of the residual source since 1999. The bacterial and archaeal consortia in groundwater obtained from the residual source were assessed by using PCR-amplified 16S rRNA genes. A clone library of bacterial amplicons was predominated by those from members of the class Clostridia (57 of 93 clones), of which a phylotype most similar to that of the homoacetogen Acetobacterium sp. strain HAAP-1 was most abundant (32 of 93 clones). The remaining Bacteria consisted of phylotypes affiliated with Sphingobacteria, Bacteroides, Spirochaetes, Mollicutes, and Proteobacteria and candidate divisions OP11 and OP3. The two proteobacterial phylotypes were most similar to those of the known dechlorinators Trichlorobacter thiogenes and Sulfurospirillum multivorans. Although not represented by the bacterial clones generated with broad-specificity bacterial primers, a Dehalococcoides-like phylotype was identified with genus-specific primers. Only four distinct phylotypes were detected in the groundwater archaeal library, including predominantly a clone affiliated with the strictly acetoclastic methanogen Methanosaeta concilii (24 of 43 clones). A mixed culture that completely dechlorinates TCE to ethene was enriched from this groundwater, and both communities were characterized by terminal restriction fragment length polymorphism (T-RFLP). According to T-RFLP, the laboratory enrichment community was less diverse overall than the groundwater community, with 22 unique phylotypes as opposed to 43 and a higher percentage of Clostridia, including the Acetobacterium population. Bioreactor archaeal structure was very similar to that of the groundwater community, suggesting that methane is

Characterization of a microbial consortium capable of rapid and simultaneous dechlorination of 1,1,2,2-tetrachloroethane and chlorinated ethane and ethene intermediates:

USGS Publications Warehouse

Jones, Elizabeth J.P.; Voytek, Mary A.; Lorah, Michelle M.; Kirshtein, Julie D.

2006-01-01

Mixed cultures capable of dechlorinating chlorinated ethanes and ethenes were enriched from contaminated wetland sediment at Aberdeen Proving Ground (APG) Maryland. The “West Branch Consortium” (WBC-2) was capable of degrading 1,1,2,2-tetrachloroethane (TeCA), trichloroethene (TCE), cis and trans 1,2-dichloroethene (DCE), 1,1,2-trichloroethane (TCA), 1,2-dichloroethane, and vinyl chloride to nonchlorinated end products ethene and ethane. WBC-2 dechlorinated TeCA, TCA, and cisDCE rapidly and simultaneously. A Clostridium sp. phylogenetically closely related to an uncultured member of a TCE-degrading consortium was numerically dominant in the WBC-2 clone library after 11 months of enrichment in culture. Clostridiales, including Acetobacteria, comprised 65% of the bacterial clones in WBC-2, with Bacteroides (14%), and epsilon Proteobacteria (14%) also numerically important. Methanogens identified in the consortium were members of the class Methanomicrobia, which includes acetoclastic methanogens. Dehalococcoidesdid not become dominant in the culture, although it was present at about 1% in the microbial population. The WBC-2 consortium provides opportunities for the in situbioremediation of sites contaminated with mixtures of chlorinated ethenes and ethanes.

Assessment of In-Situ Reductive Dechlorination Using Compound-Specific Stable Isotopes, Functional-Gene Pcr, and Geochemical Data

PubMed Central

Carreón-Diazconti, Concepción; Santamaría, Johanna; Berkompas, Justin; Field, James A.; Brusseau, Mark L.

2010-01-01

Isotopic analysis and molecular-based bioassay methods were used in conjunction with geochemical data to assess intrinsic reductive dechlorination processes for a chlorinated-solvent contaminated site in Tucson, Arizona. Groundwater samples were obtained from monitoring wells within a contaminant plume comprising tetrachloroethene and its metabolites trichloroethene, cis-1,2-dichloroethene, vinyl chloride, and ethene, as well as compounds associated with free-phase diesel present at the site. Compound specific isotope (CSI) analysis was performed to characterize biotransformation processes influencing the transport and fate of the chlorinated contaminants. PCR analysis was used to assess the presence of indigenous reductive dechlorinators. The target regions employed were the 16s rRNA gene sequences of Dehalococcoides sp. and Desulfuromonas sp., and DNA sequences of genes pceA, tceA, bvcA, and vcrA, which encode reductive dehalogenases. The results of the analyses indicate that relevant microbial populations are present and that reductive dechlorination is presently occurring at the site. The results further show that potential degrader populations as well as biotransformation activity is non-uniformly distributed within the site. The results of laboratory microcosm studies conducted using groundwater collected from the field site confirmed the reductive dechlorination of tetrachloroethene to dichloroethene. This study illustrates the use of an integrated, multiple-method approach for assessing natural attenuation at a complex chlorinated-solvent contaminated site. PMID:19603638

Fingerprinting TCE in a bedrock aquifer using compound-specific isotope analysis.

PubMed

Lojkasek-Lima, Paulo; Aravena, Ramon; Parker, Beth L; Cherry, John A

2012-01-01

A dual isotope approach based on compound-specific isotope analysis (CSIA) of carbon (C) and chlorine (Cl) was used to identify sources of persistent trichloroethylene (TCE) that caused the shut-down in 1994 of a municipal well in an extensive fractured dolostone aquifer beneath Guelph, Ontario. Several nearby industrial properties have known subsurface TCE contamination; however, only one has created a comprehensive monitoring network in the bedrock. The impacted municipal well and many monitoring wells were sampled for volatile organic compounds (VOCs), inorganic parameters, and CSIA. A wide range in isotope values was observed at the study site. The TCE varies between -35.6‰ and -21.8‰ and from 1.6‰ to 3.2‰ for δ(13) C and δ(37) Cl, respectively. In case of cis-1,2-dichloroethene, the isotope values range between -36.3‰ and -18.9‰ and from 2.4‰ to 4.7‰ for δ(13) C and δ(37) Cl, respectively. The dual isotope approach represented by a plot of δ(13) C vs. δ(37) Cl shows the municipal well samples grouped in a domain clearly separate from all other samples from the property with the comprehensive well network. The CSIA results collected under non-pumping and short-term pumping conditions thus indicate that this particular property, which has been studied intensively for several years, is not a substantial contributor of the TCE presently in the municipal well under non-pumping conditions. This case study demonstrates that CSIA signatures would have been useful much earlier in the quest to examine sources of the TCE in the municipal well if bedrock monitoring wells had been located at several depths beneath each of the potential TCE-contributing properties. Moreover, the CSIA results show that microbial reductive dechlorination of TCE occurs in some parts of the bedrock aquifer. At this site, the use of CSIA for C and Cl in combination with analyses of VOC and redox parameters proved to be important due to the complexity introduced by

Field-scale demonstration of induced biogeochemical reductive dechlorination at Dover Air Force Base, Dover, Delaware

NASA Astrophysics Data System (ADS)

Kennedy, Lonnie G.; Everett, Jess W.; Becvar, Erica; DeFeo, Donald

2006-11-01

Biogeochemical reductive dechlorination (BiRD) is a new remediation approach for chlorinated aliphatic hydrocarbons (CAHs). The approach stimulates common sulfate-reducing soil bacteria, facilitating the geochemical conversion of native iron minerals into iron sulfides. Iron sulfides have the ability to chemically reduce many common CAH compounds including PCE, TCE, DCE, similar to zero valent iron (Fe 0). Results of a field test at Dover Air Force Base, Dover, Delaware, are given in this paper. BiRD was stimulated by direct injection of Epson salt (MgSO 4·7H 2O) and sodium (L) lactate (NaC 3H 5O 3) in five injection wells. Sediment was sampled before and 8 months after injection. Significant iron sulfide minerals developed in the sandy aquifer matrix. From ground water analyses, treatment began a few weeks after injection with up to 95% reduction in PCE, TCE, and cDCE in less than 1 year. More complete CAH treatment is likely at a larger scale than this demonstration.

Successful operation of continuous reactors at short retention times results in high-density, fast-rate Dehalococcoides dechlorinating cultures.

PubMed

Delgado, Anca G; Fajardo-Williams, Devyn; Popat, Sudeep C; Torres, César I; Krajmalnik-Brown, Rosa

2014-03-01

The discovery of Dehalococcoides mccartyi reducing perchloroethene and trichloroethene (TCE) to ethene was a key landmark for bioremediation applications at contaminated sites. D. mccartyi-containing cultures are typically grown in batch-fed reactors. On the other hand, continuous cultivation of these microorganisms has been described only at long hydraulic retention times (HRTs). We report the cultivation of a representative D. mccartyi-containing culture in continuous stirred-tank reactors (CSTRs) at a short, 3-d HRT, using TCE as the electron acceptor. We successfully operated 3-d HRT CSTRs for up to 120 days and observed sustained dechlorination of TCE at influent concentrations of 1 and 2 mM TCE to ≥ 97 % ethene, coupled to the production of 10(12) D. mccartyi cells Lculture (-1). These outcomes were possible in part by using a medium with low bicarbonate concentrations (5 mM) to minimize the excessive proliferation of microorganisms that use bicarbonate as an electron acceptor and compete with D. mccartyi for H2. The maximum conversion rates for the CSTR-produced culture were 0.13 ± 0.016, 0.06 ± 0.018, and 0.02 ± 0.007 mmol Cl(-) Lculture (-1) h(-1), respectively, for TCE, cis-dichloroethene, and vinyl chloride. The CSTR operation described here provides the fastest laboratory cultivation rate of high-cell density Dehalococcoides cultures reported in the literature to date. This cultivation method provides a fundamental scientific platform for potential future operations of such a system at larger scales.

Consideration of Treatment Performance Assessment Metrics for a TCE Source Area Bioremediation (SABRe project)

NASA Astrophysics Data System (ADS)

Cai, Z.; Wilson, R. D.

2009-05-01

Techniques for optimizing the removal of NAPL mass in source zones have advanced at a more rapid rate than strategies to assess treatment performance. Informed selection of remediation approaches would be easier if measurements of performance were more directly transferable. We developed a number of methods based on data generated from multilevel sampler (MLS) transects to assess the effectiveness of a bioaugmentation/biostimulation trial in a TCE source residing in a terrace gravel aquifer in the East Midlands, UK. In this spatially complex aquifer, treatment inferred from long screen monitoring well data was not as reliable as that from consideration of mass flux changes across transects installed in and downgradient of the source. Falling head tests were conducted in the MLS ports to generate the necessary hydraulic conductivity (K) data. Combining K with concentration provides a mass flux map that allows calculation of mass turnover and an assessment of where in the complex geology the greatest turnover occurred. Five snapshots over a 600-day period indicate a marked reduction in TCE flux, suggesting a significant reduction in DNAPL mass over that expected due to natural processes. However, persistence of daughter products suggested that complete dechlorination did not occur. The MLS fence data also revealed that delivery of both carbon source and pH buffer were not uniform across the test zone. This may have lead to the generation of niches of iron(III) and sulphate reduction as well as methanogenesis, which impacted on dechlorination processes. In the absence of this spatial data, it is difficult to reconcile apparent treatment as indicated in monitoring well data to on-going processes.

Mechanism insights into enhanced trichloroethylene removal using xanthan gum-modified microscale zero-valent iron particles.

PubMed

Xin, Jia; Han, Jun; Zheng, Xilai; Shao, Haibing; Kolditz, Olaf

2015-03-01

This report focuses on the enhancement in trichloroethylene (TCE) removal from contaminated groundwater using xanthan gum (XG)-modified, microscale, zero-valent iron (mZVI). Compared with bare mZVI, XG-coated mZVI increased the TCE removal efficiency by 30.37% over a 480-h experimental period. Because the TCE removal is attributed to both sorption and reduction processes, the contributions from sorption and reduction were separately investigated to determine the mechanism of XG on TCE removal using mZVI. The results showed that the TCE sorption capacity of mZVI was lower in the presence of XG, whereas the TCE reduction capacity was significantly increased. The FTIR spectra confirmed that XG, which is rich in hydrophilic functional groups, was adsorbed onto the iron surface through intermolecular hydrogen bonds, which competitively repelled the sorption and mass transfer of TCE toward reactive sites. The variations in the pH, Eh, and Fe(2+) concentration as functions of the reaction time were recorded and indicated that XG buffered the solution pH, inhibited surface passivation, and promoted TCE reduction by mZVI. Overall, the XG-modified mZVI was considered to be potentially effective for the in-situ remediation of TCE contaminated groundwater due to its high stability and dechlorination reactivity. Copyright © 2014 Elsevier Ltd. All rights reserved.

Anaerobic bacteria that dechlorinate perchloroethene.

PubMed Central

Fathepure, B Z; Nengu, J P; Boyd, S A

1987-01-01

In this study, we identified specific cultures of anaerobic bacteria that dechlorinate perchlorethene (PCE). The bacteria that significantly dechlorinated PCE were strain DCB-1, an obligate anaerobe previously shown to dechlorinate chlorobenzoate, and two strains of Methanosarcina. The rate of PCE dechlorination by DCB-1 compared favorably with reported rates of trichloroethene bio-oxidation by methanotrophs. Even higher PCE dechlorination rates were achieved when DCB-1 was grown in a methanogenic consortium. PMID:3426224

Potential of the TCE-degrading endophyte Pseudomonas putida W619-TCE to improve plant growth and reduce TCE phytotoxicity and evapotranspiration in poplar cuttings.

PubMed

Weyens, Nele; Truyens, Sascha; Dupae, Joke; Newman, Lee; Taghavi, Safiyh; van der Lelie, Daniel; Carleer, Robert; Vangronsveld, Jaco

2010-09-01

The TCE-degrading poplar endophyte Pseudomonas putida W619-TCE was inoculated in poplar cuttings, exposed to 0, 200 and 400 mg l(-1) TCE, that were grown in two different experimental setups. During a short-term experiment, plants were grown hydroponically in half strength Hoagland nutrient solution and exposed to TCE for 3 days. Inoculation with P. putida W619-TCE promoted plant growth, reduced TCE phytotoxicity and reduced the amount of TCE present in the leaves. During a mid-term experiment, plants were grown in potting soil and exposed to TCE for 3 weeks. Here, inoculation with P. putida W619-TCE had a less pronounced positive effect on plant growth and TCE phytotoxicity, but resulted in strongly reduced amounts of TCE in leaves and roots of plants exposed to 400 mg l(-1) TCE, accompanied by a lowered evapotranspiration of TCE. Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), which are known intermediates of TCE degradation, were not detected. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Electron transfer from a solid-state electrode assisted by methyl viologen sustains efficient microbial reductive dechlorination of TCE.

PubMed

Aulenta, Federico; Catervi, Alessandro; Majone, Mauro; Panero, Stefania; Reale, Priscilla; Rossetti, Simona

2007-04-01

The ability to transfer electrons, via an extracellular path, to solid surfaces is typically exploited by microorganisms which use insoluble electron acceptors, such as iron-or manganese-oxides or inert electrodes in microbial fuel cells. The reverse process, i.e., the use of solid surfaces or electrodes as electron donors in microbial respirations, although largely unexplored, could potentially have important environmental applications, particularly for the removal of oxidized pollutants from contaminated groundwater or waste streams. Here we show, for the first time, that an electrochemical cell with a solid-state electrode polarized at -500 mV (vs standard hydrogen electrode), in combination with a low-potential redox mediator (methyl viologen), can efficiently transfer electrochemical reducing equivalents to microorganisms which respire using chlorinated solvents. By this approach, the reductive transformation of trichloroethene, a toxic yet common groundwater contaminant, to harmless end-products such as ethene and ethane could be performed. Furthermore, using a methyl-viologen-modified electrode we could even demonstrate that dechlorinating bacteria were able to accept reducing equivalents directly from the modified electrode surface. The innovative concept, based on the stimulation of dechlorination reactions through the use of solid-state electrodes (we propose for this process the acronym BEARD: Bio-Electrochemically Assisted Reductive Dechlorination), holds promise for in situ bioremediation of chlorinated-solvent-contaminated groundwater, and has several potential advantages over traditional approaches based on the subsurface injection of organic compounds. The results of this study raise the possibility that immobilization of selected redox mediators may be a general strategy for stimulating and controlling a range of microbial reactions using insoluble electrodes as electron donors.

Protistan Predation Affects Trichloroethene Biodegradation in a Bedrock Aquifer▿

PubMed Central

Cunningham, Joseph J.; Kinner, Nancy E.; Lewis, Maureen

2009-01-01

Despite extensive research on the bottom-up force of resource availability (e.g., electron donors and acceptors), slow biodegradation rates and stalling at cis-dichloroethene (cDCE) and vinyl chloride continue to be observed in aquifers contaminated with trichloroethene (TCE). The objective of this research was to gauge the impact of the top-down force of protistan predation on TCE biodegradation in laboratory microcosms. When indigenous bacteria from an electron donor-limited TCE-contaminated bedrock aquifer were present, the indigenous protists inhibited reductive dechlorination altogether. The presence of protists during organic carbon-amended conditions caused the bacteria to elongate (length:width, ≥10:1), but reductive dechlorination was still inhibited. When a commercially available dechlorinating bacterial culture and an organic carbon amendment were added in he presence of protists, the elongated bacteria predominated and reductive dechlorination stalled at cDCE. When protists were removed under organic carbon-amended conditions, reductive dechlorination stalled at cDCE, whereas in the presence organic carbon and bacterial amendments, the total chlorinated ethene concentration decreased, indicating TCE was converted to ethene and/or CO2. The data suggested that indigenous protists grazed dechlorinators to extremely low levels, inhibiting dechlorination altogether. Hence, in situ bioremediation/bioaugmentation may not be successful in mineralizing TCE unless the top-down force of protistan predation is inhibited. PMID:19820148

Wheat straw biochar-supported nanoscale zerovalent iron for removal of trichloroethylene from groundwater.

PubMed

Li, Hui; Chen, Ya Qin; Chen, Shuai; Wang, Xiao Li; Guo, Shu; Qiu, Yue Feng; Liu, Yong Di; Duan, Xiao Li; Yu, Yun Jiang

2017-01-01

This study synthesized the wheat straw biochar-supported nanoscale zerovalent iron (BC-nZVI) via in-situ reduction with NaBH4 and biochar pyrolyzed at 600°C. Wheat straw biochar, as a carrier, significantly enhanced the removal of trichloroethylene (TCE) by nZVI. The pseudo-first-order rate constant of TCE removal by BC-nZVI (1.079 h-1) within 260 min was 1.4 times higher and 539.5 times higher than that of biochar and nZVI, respectively. TCE was 79% dechlorinated by BC-nZVI within 15 h, but only 11% dechlorinated by unsupported nZVI, and no TCE dechlorination occurred with unmodified biochar. Weakly acidic solution (pH 5.7-6.8) significantly enhanced the dechlorination of TCE. Chloride enhanced the removal of TCE, while SO42-, HCO3- and NO3- all inhibited it. Humic acid (HA) inhibited BC-nZVI reactivity, but the inhibition decreased slightly as the concentration of HA increased from 40 mg∙L-1 to 80 mg∙L-1, which was due to the electron shutting by HA aggregates. Results suggest that BC-nZVI was promising for remediation of TCE contaminated groundwater.

Metabolic adaptation and in situ attenuation of chlorinated ethenes by naturally occurring microorganisms in a fractured dolomite aquifer near Niagara Falls, New York

USGS Publications Warehouse

Yager, R.M.; Bilotta, S.E.; Mann, C.L.; Madsen, E.L.

1997-01-01

A combination of hydrogeological, geochemical, and microbiological methods was used to document the biotransformation of trichloroethene (TCE) to ethene, a completely dechlorinated and environmentally benign compound, by naturally occurring microorganisms within a fractured dolomite aquifer. Analyses of groundwater samples showed that three microbially produced TCE breakdown products (cis-1,2-dichloroethene, vinyl chloride, and ethene) were present in the contaminant plume. Hydrogen (H2) concentrations in groundwater indicated that iron reduction was the predominant terminal electron-accepting process in the most contaminated geologic zone of the site. Laboratory microcosms prepared with groundwater demonstrated complete sequential dechlorination of TCE to ethene. Microcosm assays also revealed that reductive dechlorination activity was present in waters from the center but not from the periphery of the contaminant plume. This dechlorination activity indicated that naturally occurring microorganisms have adapted to utilize chlorinated ethenes and suggested that dehalorespiring rather than cometabolic, microbial processes were the cause of the dechlorination. The addition of pulverized dolomite to microcosms enhanced the rate of reductive dechlorination, suggesting that hydrocarbons in the dolomite aquifer may serve as electron donors to drive microbially mediated reductive dechlorination reactions. Biodegradation of the chlorinated ethenes appears to contribute significantly to decontamination of the site.A combination of hydrogeological, geochemical, and microbiological methods was used to document the biotransformation of trichloroethene (TCE) to ethene, a completely dechlorinated and environmentally benign compound, by naturally occurring microorganisms within a fractured dolomite aquifer. Analyses of groundwater samples showed that three microbially produced TCE breakdown products (cis-1,2-dichloroethene, vinyl chloride, and ethene) were present in the

Enhanced reductive de-chlorination of a solvent contaminated aquifer through addition and apparent fermentation of cyclodextrin

NASA Astrophysics Data System (ADS)

Blanford, William James; Pecoraro, Michael Philip; Heinrichs, Rebecca; Boving, Thomas Bernhard

2018-01-01

In a field study, aqueous cyclodextrin (CD) was investigated for its ability to extract chlorinated volatile organic compounds (cVOC), such as trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), and dichloroethene (DCE) through in-situ flushing of a sandy aquifer. After cessation of aquifer flushing, a plume of CD was left. Changes in CD, cVOC, and inorganic terminal electron acceptors (TEAs) (DO, nitrate, sulfate, iron) were monitored in four rounds of wellwater sampling (20, 210, 342, and 425 days after cessation of active pumping). Post-CD flushing VOC levels rebounded (850% for TCE, 190% for TCA, and 53% for DCE) between the first two sampling rounds, apparently due to rate-limited desorption from aquifer media and dissolution from remaining NAPL. However, substantial reduction in the mass of TCE (6.3 to 0.11 mol: 98%) and TCA (2.8 to 0.73 mol: 74%) in groundwater was observed between 210 and 425 days. DCE should primarily be produced from the degradation of TCE and is expected to subsequently degrade to chloroethene. Since DCE levels decreased only slightly (0.23 to 0.17 mol: 26%), its degradation rate should be similar to that produced from the decaying TCE. Cyclodextrin was monitored starting from day 210. The mass of residual CD (as measured by Total Organic Carbon) decreased from 150 mol (day 210) to 66 (day 425) (56% decrease). The naturally anaerobic zone within the aquifer where residual CD mass decreased coincided with a loss of other major potential TEAs: nitrate (97% loss), sulfate (31%) and iron (31%). In other studies, TCE and 1,1,1-TCA have been found to be more energetically favorable TEAs than sulfate and iron and their degradation via reductive dechlorination has been found to be enhanced by the fermentation of carbohydrates. Such processes can explain these observations, but more investigation is needed to evaluate whether residual levels of CD can facilitate the anaerobic degradation of chlorinated VOCs.

Biodegradation analyses of trichloroethylene (TCE) by bacteria and its use for biosensing of TCE.

PubMed

Chee, Gab-Joo

2011-09-30

Trichloroethylene (TCE) is a toxic, recalcitrant groundwater pollutant. TCE-degrading microorganisms were isolated from various environments. The aerobic bacteria isolated from toluene- and tryptophan-containing media were Pseudomonas sp. strain ASA86 and Burkholderia sp. strain TAM17, respectively; these are necessary for inducing TCE biodegradation in a selective medium. The half-degradation time of TCE to a concentration of 1mg/L was 18 h for strain ASA86 and 7 days for strain TAM17. While identifying toluene/TCE degradation genes, we found that in strain ASA86, the gene was the same as the todC1 gene product encoding toluene dioxygenase identified in Pseudomonas putida F1, and that in strain TAM17, the gene was similar to the tecA1 gene product encoding chlorobenzene dioxygenase identified in Burkholderia sp. PS12. A novel TCE biosensor was developed using strain ASA86 as the inducer of toluene under aerobic conditions. The TCE biosensor exhibited a linear relationship below 3 ppm TCE. Detection limit of the biosensor was 0.05 ppm TCE. The response time of the biosensor was less than 10 min. The biosensor response displayed a constant level during a 2 day period. The TCE biosensor displayed sufficient sensitivity for monitoring TCE in environmental systems. Copyright © 2011 Elsevier B.V. All rights reserved.

Methanogenic community development in anaerobic granular bioreactors treating trichloroethylene (TCE)-contaminated wastewater at 37 °C and 15 °C.

PubMed

Siggins, Alma; Enright, Anne-Marie; O'Flaherty, Vincent

2011-04-01

Four expanded granular sludge bed (EGSB) bioreactors were seeded with a mesophilically-grown granular sludge and operated in duplicate for mesophilic (37 °C; R1 & R2) and low- (15°; R3 & R4) temperature treatment of a synthetic volatile fatty acid (VFA) based wastewater (3 kg COD m(-3) d(-1)) with one of each pair (R1 & R3) supplemented with increasing concentrations of trichloroethylene (TCE; 10, 20, 40, 60 mg l(-1)) and one acting as a control. Bioreactor performance was evaluated by % COD removal efficiency and % biogas methane (CH(4)) content. Quantitative Polymerase Chain Reaction (qPCR) was used to investigate the methanogenic community composition and dynamics in the bioreactors during the trial, while specific methanogenic activity (SMA) and toxicity assays were utilized to investigate the activity and TCE/dichloroethylene (DCE) toxicity thresholds of key trophic groups, respectively. At both 37 °C and 15 °C, TCE levels of 60 mg l(-1) resulted in the decline of % COD removal efficiencies to 29% (Day 235) and 37% (Day 238), respectively, and in % biogas CH(4) to 54% (Day 235) and 5% (Day 238), respectively. Despite the inhibitory effect of TCE on the anaerobic digestion process, the main drivers influencing methanogenic community development, as determined by qPCR and Non-metric multidimensional scaling analysis, were (i) wastewater composition and (ii) operating temperature. At the apical TCE concentration both SMA and qPCR of methanogenic archaea suggested that acetoclastic methanogens were somewhat inhibited by the presence of TCE and/or its degradation derivatives, while competition by dechlorinating organisms may have limited the availability of H(2) for hydrogenotrophic methanogenesis. In addition, there appeared to be an inverse correlation between SMA levels and TCE tolerance, a finding that was supported by the analysis of the inhibitory effect of TCE on two additional biomass sources. The results indicate that low-temperature anaerobic

Wheat straw biochar-supported nanoscale zerovalent iron for removal of trichloroethylene from groundwater

PubMed Central

Li, Hui; Chen, Ya Qin; Chen, Shuai; Wang, Xiao Li; Guo, Shu; Qiu, Yue Feng; Liu, Yong Di; Duan, Xiao Li; Yu, Yun Jiang

2017-01-01

This study synthesized the wheat straw biochar-supported nanoscale zerovalent iron (BC-nZVI) via in-situ reduction with NaBH4 and biochar pyrolyzed at 600°C. Wheat straw biochar, as a carrier, significantly enhanced the removal of trichloroethylene (TCE) by nZVI. The pseudo-first-order rate constant of TCE removal by BC-nZVI (1.079 h−1) within 260 min was 1.4 times higher and 539.5 times higher than that of biochar and nZVI, respectively. TCE was 79% dechlorinated by BC-nZVI within 15 h, but only 11% dechlorinated by unsupported nZVI, and no TCE dechlorination occurred with unmodified biochar. Weakly acidic solution (pH 5.7–6.8) significantly enhanced the dechlorination of TCE. Chloride enhanced the removal of TCE, while SO42−, HCO3− and NO3− all inhibited it. Humic acid (HA) inhibited BC-nZVI reactivity, but the inhibition decreased slightly as the concentration of HA increased from 40 mg∙L-1 to 80 mg∙L-1, which was due to the electron shutting by HA aggregates. Results suggest that BC-nZVI was promising for remediation of TCE contaminated groundwater. PMID:28264061

Understanding pH Effects on Trichloroethylene and Perchloroethylene Adsorption to Iron in Permeable Reactive Barriers for Groundwater Remediation.

PubMed

Luo, Jing; Farrell, James

2013-01-01

Metallic iron filings are becoming increasing used in permeable reactive barriers for remediating groundwater contaminated by chlorinated solvents. Understanding solution pH effects on rates of reductive dechlorination in permeable reactive barriers is essential for designing remediation systems that can meet treatment objectives under conditions of varying groundwater properties. The objective of this research was to investigate how the solution pH value affects adsorption of trichloroethylene (TCE) and perchloroethylene (PCE) on metallic iron surfaces. Because adsorption is first required before reductive dechlorination can occur, pH effects on halocarbon adsorption energies may explain pH effects on dechlorination rates. Adsorption energies for TCE and PCE were calculated via molecular mechanics simulations using the Universal force field and a self-consistent reaction field charge equilibration scheme. A range in solution pH values was simulated by varying the amount of atomic hydrogen adsorbed on the iron. The potential energies associated TCE and PCE complexes were dominated by electrostatic interactions, and complex formation with the surface was found to result in significant electron transfer from the iron to the adsorbed halocarbons. Adsorbed atomic hydrogen was found to lower the energies of TCE complexes more than those for PCE. Attractions between atomic hydrogen and iron atoms were more favorable when TCE versus PCE was adsorbed to the iron surface. These two findings are consistent with the experimental observation that changes in solution pH affect TCE reaction rates more than those for PCE.

Monitoring Anaerobic TCE Degradation by Evanite Cultre in Column Packed with TCE-Contaminated Soil

NASA Astrophysics Data System (ADS)

Ko, J.; Han, K.; Ahn, G.; Park, S.; Kim, N.; Ahn, H.; Kim, Y.

2011-12-01

Trichloroethylene (TCE) is a long-term common groundwater pollutant because the compound with high density is slowly released into groundwater. Physical and chemical remediation processes have been used to clean-up the contaminant, but novel remediation technology is required to overcome a low efficiency of the traditional treatment process. Many researchers focused on biological process using an anaerobic TCE degrading culture, dehalococcoides spp., but it still needs to evaluate whether the process can be applied into field scale under aerobic condition. Therefore, in this work we examined two different types (i.e., Natural attenuation and bioaugmentation) of biological remediation process in anaerobic column packed with TCE-contaminated soil. A TCE degradation by indigenous microorganisms was confirmed by monitoring TCE and the metabolites (c-DCE, VC, ETH). However, TCE was transformed and stoichiometry amount of c-DCE was produced, and VC and ETH was not detected. To test bioaugmentation of Evanite culture containing dehalococcoides spp., Evanite culture was injected into the column and TCE degradation to c-DCE, VC, ETH was monitored. We are evaluating the transport of the Evanite culture in the column by measuring TCE and VC reductases. In the result, the TCE was completely degraded to ETH using hydrogen as electron donor generate by hydrogen-production fermentation from formate.

Reductive Dechlorination of Carbon Tetrachloride by Tetrachloroethene and Trichloroethene Respiring Anaerobic Mixed Cultures

NASA Astrophysics Data System (ADS)

Vickstrom, K. E.; Azizian, M.; Semprini, L.

2015-12-01

Carbon tetrachloride (CT) is a toxic and recalcitrant groundwater contaminant with the potential to form a broad range of transformation products. Of the possible biochemical pathways through which CT can be degraded, reductive dehalogenation to less chlorinated compounds and mineralization to carbon dioxide (CO2) appear to be the most frequently utilized pathways by anaerobic organisms. Results will be presented from batch experiments of CT degradation by the Evanite (EV), Victoria Strain (VS) and Point Mugu (PM) anaerobic dechlorinating cultures. The cultures are grown in chemostats and are capable of transforming tetrachloroethene (PCE) or trichloroethene (TCE) to ethene by halorespiration via reductive dehalogenase enzymes. For the batch CT transformation tests, the cells along with supernatant were harvested from chemostats fed PCE or TCE, but never CT. The batch reactors were initially fed 0.0085 mM CT and an excess of formate (EV and VS) or lactate (PM) as electron donor. Transformation of CT was 100% with about 20% converted to chloroform (CF) and undetected products. Multiple additions of CT showed a slowing of pseudo first-order CT transformation rates across all cultures. Batch reactors were then established and fed 0.085 mM CT with an excess of electron donor in order to better quantify the reductive pathway. CT was transformed to CF and dichloromethane (DCM), with trace amounts of chloromethane (CM) detected. Between 60-90% of the mass added to the system was accounted for, showing that the majority of the carbon tetrachloride present is being reductively dehalogenated. Results from batch reactors that were poisoned using sodium azide, and from reactors not provided electron donor will be presented to distinguish between biotic and abiotic reactions. Furthermore, results from reactors prepared with acetylene (a potent, reversible inhibitor of reductive dehalogenases (1)) will be presented as a means of identifying the enzymes involved in the

Anaerobic Transformation of Chlorinated Aliphatic Hydrocarbons in a Sand Aquifer Based on Spatial Chemical Distributions

NASA Astrophysics Data System (ADS)

Semprini, Lewis; Kitanidis, Peter K.; Kampbell, Don H.; Wilson, John T.

1995-04-01

We estimated the distribution of chlorinated aliphatic hydrocarbons (CAHs) from groundwater samples collected along three transects in a sand aquifer. Trichloroethylene (TCE) leaked and contaminated the aquifer probably more than a decade before we collected the measurements. The data show significant concentrations of TCE, cis-l,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethene. We attributed DCE, VC, and ethene to the reductive dehalogenation of TCE. The CAH concentrations varied significantly with depth and correlate with sulfate and methane concentrations. Anoxic aquifer conditions exist with methane present at relatively high concentrations at depth. High concentrations of TCE correspond with the absence of methane or low methane concentrations, whereas products of TCE dehalogenation are associated with higher methane concentrations and low sulfate concentrations. Indications are that the dechlorination of TCE and DCE to VC and ethene is associated with sulfate reduction and active methanogenesis. TCE dechlorination to DCE is likely occurring under the less reducing conditions of sulfate reduction, with further reductions to VC and ethene occurring under methanogenic conditions. We estimated that about 20% of TCE has dechlorinated to ethene. The analysis of the data enhanced our knowledge of natural in situ transformation and transport processes of CAHs.

Performance and Mechanism of Piezo-Catalytic Degradation of 4-Chlorophenol: Finding of Effective Piezo-Dechlorination.

PubMed

Lan, Shenyu; Feng, Jinxi; Xiong, Ya; Tian, Shuanghong; Liu, Shengwei; Kong, Lingjun

2017-06-06

Piezo-catalysis was first used to degrade a nondye pollutant, 4-chlorophenol (4-CP). In this process, hydrothermally synthesized tetragonal BaTiO 3 nano/micrometer-sized particles were used as the piezo-catalyst, and the ultrasonic irradiation with low frequency was selected as the vibration energy to cause the deformation of tetragonal BaTiO 3 . It was found that the piezoelectric potential from the deformation could not only successfully degrade 4-chlorophenol but also effectively dechlorinate it at the same time, and five kinds of dechlorinated intermediates, hydroquinone, benzoquinone, phenol, cyclohexanone, and cyclohexanol, were determined. This is the first sample of piezo-dechlorination. Although various active species, including h + , e - , •H, •OH, •O 2 - , 1 O 2 , and H 2 O 2 , were generated in the piezoelectric process, it was confirmed by ESR, scavenger studies, and LC-MS that the degradation and dechlorination were mainly attributed to •OH radicals. These •OH radicals were chiefly derived from the electron reduction of O 2 , partly from the hole oxidation of H 2 O. These results indicated that the piezo-catalysis was an emerging and effective advanced oxidation technology for degradation and dechlorination of organic pollutants.

Assessment of potential positive effects of nZVI surface modification and concentration levels on TCE dechlorination in the presence of competing strong oxidants, using an experimental design.

PubMed

Kaifas, Delphine; Malleret, Laure; Kumar, Naresh; Fétimi, Wafa; Claeys-Bruno, Magalie; Sergent, Michelle; Doumenq, Pierre

2014-05-15

Nanoscale zero-valent iron (nZVI) particles are efficient for the remediation of aquifers polluted by trichloroethylene (TCE). But for on-site applications, their reactivity can be affected by the presence of common inorganic co-pollutants, which are equally reduced by nZVI particles. The aim of this study was to assess the potential positive effects of nZVI surface modification and concentration level on TCE removal in the concomitant presence of two strong oxidants, i.e., Cr(VI) and NO3(-). A design of experiments, testing four factors (i.e. nZVI concentration, nZVI surface modification, Cr(VI) concentration and NO3(-) concentration), was used to select the best trials for the identification of the main effects of the factors and of the factors interactions. The effects of these factors were studied by measuring the following responses: TCE removal rates at different times, degradation kinetic rates, and the transformation products formed. As expected, TCE degradation was delayed or inhibited in most of the experiments, due to the presence of inorganics. The negative effects of co-pollutants can be palliated by combining surface modification with a slight increase in nZVI concentration. Encouragingly, complete TCE removal was achieved for some given experimental conditions. Noteworthily, nZVI surface modification was found to promote the efficient degradation of TCE. When degradation occurred, TCE was mainly transformed into innocuous non-chlorinated transformation products, while hazardous chlorinated transformation products accounted for a small percentage of the mass-balance. Copyright © 2014 Elsevier B.V. All rights reserved.

TCE treatment pasta-bilities.

PubMed Central

Holton, W C

1999-01-01

Monsanto's "Lasagna" process uses layers of treatment zones spaced between buried electrodes to remove trichloroethylene (TCE) from contaminated soil and groundwater. TCE is used primarily as a metal degreaser as well as in products such as dyes, printing ink, and paint. TCE can eventually make its way into the environment and is prevalent in the water and soil of industrialized nations. Although TCE breaks down in a few days when released into the atmosphere, it degrades much more slowly in soil, taking months or years. Moreover, it is often broken down by microbes into toxic substances such as vinylidene chloride (a suspected human carcinogen) and vinyl chloride (a known human carcinogen). The Lasagna process is based on the principle of electro-osmosis, in which an electric current draws water from low--permeability soils such as clays, silts, and fine sands. To remove TCE from contaminated soils, Monsanto scientists added layers of filtering media, which attack the contaminant as it is pulled from electrode to electrode. The technology has been tested at the Paducah Gaseous Diffusion Plant in western Kentucky, where it removed over 98% of TCE from contaminated soil. PMID:10464086

a Novel Catalyst for Reductive Dechlorination of Chlorobenzene in Subcritical Water:. Bifunctional Fe/ZrO2

NASA Astrophysics Data System (ADS)

Wei, Guang-Tao; Wei, Chao-Hai; He, Feng-Mei; Wu, Chao-Fei

Bifunctional Fe/ZrO2 was prepared by mechanical mixing method, and its bifunctional effect on reductive dechlorination of chlorobenzene in subcritical water was studied. Dechlorination efficiency increased with increasing iron content in catalyst and catalyst amount. Dechlorination efficiency slowed when the iron content in catalyst reached 30%; bifunctional catalyst of Fe/ZrO2 was more efficient in dechlorination of chlorobenzene than Fe alone. Catalyst of Fe (30%)/ZrO2 was characterized by means of X-ray diffraction (XRD), H2 temperature programmed desorption (H2-TPD), and N2 adsorption. The possible mechanism of dechlorination in subcritical water by this bifunctional catalyst was proposed. H+ produced in the water dissociation formed the highly reactive spillover hydrogen on the surface of catalyst, and then reacted with chlorobenzene adsorbed on the catalyst surface by ZrO2 to form benzene and chloride ions.

Dechlorination Mechanism of CuCl Residue from Zinc Hydrometallurgy by Microwave Roasting

NASA Astrophysics Data System (ADS)

Lu, Shuaidan; Ju, Shaohua; Peng, Jinhui; Zhu, Xiaoping; Srinivasakannan, C.; Zhang, Libo; Tu, Ganfeng

2015-04-01

Removal of chlorine (Cl) from the CuCl residue in the process of zinc hydrometallurgy is of great importance to improve the process economics. The current processing methods result in generation of large quantities of polluted discharge necessitating waste treatment systems. The present work attempts to de-chlorinate the CuCl residue through thermal treatment with application of microwave, towards which the effect of the major experimental factors such as roasting temperature, heating duration and particle size of samples on the process has been investigated. And the changes of Gibbs free energy (ΔG) of the dechlorination reactions are calculated which show that: 1) CuCl can react with H2O and air to produce CuO and HCl(g); 2) CuCl can be oxidized by air into CuO and Cl2 would be released. The tail gas chromatography, XRD and SEM-EDS analysis results of samples before and after microwave roasting verified the thermodynamics study results. Thus, the process of dechlorination by microwave roasting technology is feasible, and the tail gas can be mainly HCl(g) and air which can be absorbed with water and produce hydrochloride easily.

Chloroethene Biodegradation Potential, ADOT/PF Peger Road Maintenance Facility, Fairbanks, Alaska

USGS Publications Warehouse

Bradley, Paul M.; Chapelle, Frances H.

2004-01-01

A series of 14C-radiotracer-based microcosm experiments were conducted to assess: 1) the extent, rate and products of microbial dechlorination of trichloroethene (TCE), cis-dichloroethene (cis-DCE) and vinyl chloride (VC) in sediments at the Peger Road site; 2) the effect of three electron donor amendments (molasses, shrimp and crab chitin, and 'Hydrogen Release Compound' (HRC)) on microbial degradation of TCE in three Peger Road sediments; and 3) the potential significance at the site of chloroethene biodegradation processes other than reductive dechlorination. In these experiments, TCE biodegradation yielded the reduced products, DCE and VC, and the oxidation product CO 2. Biodegradation of DCE and VC involved stoichiometric oxidation to CO 2. Both laboratory microcosm study and field redox assessment results indicated that the predominant terminal electron accepting process in Peger Road plume sediments under anoxic conditions was Mn/Fe-reduction. The rates of chloroethene biodegradation observed in Peger Road sediment microcosms under low temperature conditions (4?C) were within the range of those observed in sediments from temperate (20?C) aquifer systems. This result confirmed that biodegradation can be a significant mechanism for in situ contaminant remediation even in cold temperature aquifers. The fact that CO2 was the sole product of cis-DCE and VC biodegradation detected in Peger Road sediments indicated that a natural attenuation assessment based on reduced daughter product accumulation may significantly underestimate the potential for DCE and VC biodegradation at the Peger Road. Neither HRC nor molasses addition stimulated TCE reductive dechlorination. The fact that molasses and HRC amendment did stimulate Mn/Fe-reduction suggests that addition of these electron donors favored microbial Mn/Fe-reduction to the detriment of microbial TCE dechlorinating activity. In contrast, amendment of sediment microcosms with shrimp and crab chitin resulted in the

The Potential of the Ni-Resistant TCE-Degrading Pseudomonas putida W619-TCE to Reduce Phytotoxicity and Improve Phytoremediation Efficiency of Poplar Cuttings on A Ni-TCE Co-Contamination.

PubMed

Weyens, Nele; Beckers, Bram; Schellingen, Kerim; Ceulemans, Reinhart; van der Lelie, Daniel; Newman, Lee; Taghavi, Safiyh; Carleer, Robert; Vangronsveld, Jaco

2015-01-01

To examine the potential of Pseudomonas putida W619-TCE to improve phytoremediation of Ni-TCE co-contamination, the effects of inoculation of a Ni-resistant, TCE-degrading root endophyte on Ni-TCE phytotoxicity, Ni uptake and trichloroethylene (TCE) degradation of Ni-TCE-exposed poplar cuttings are evaluated. After inoculation with P. putida W619-TCE, root weight of non-exposed poplar cuttings significantly increased. Further, inoculation induced a mitigation of the Ni-TCE phytotoxicity, which was illustrated by a diminished exposure-induced increase in activity of antioxidative enzymes. Considering phytoremediation efficiency, inoculation with P. putida W619-TCE resulted in a 45% increased Ni uptake in roots as well as a slightly significant reduction in TCE concentration in leaves and TCE evapotranspiration to the atmosphere. These results indicate that endophytes equipped with the appropriate characteristics can assist their host plant to deal with co-contamination of toxic metals and organic contaminants during phytoremediation. Furthermore, as poplar is an excellent plant for biomass production as well as for phytoremediation, the obtained results can be exploited to produce biomass for energy and industrial feedstock applications in a highly productive manner on contaminated land that is not suited for normal agriculture. Exploiting this land for biomass production could contribute to diminish the conflict between food and bioenergy production.

SET mediates TCE-induced liver cell apoptosis through dephosphorylation and upregulation of nucleolin

PubMed Central

Ren, Xiaohu; Huang, Xinfeng; Yang, Xifei; Liu, Yungang; Liu, Wei; Huang, Haiyan; Wu, Desheng; Zou, Fei; Liu, Jianjun

2017-01-01

Trichloroethylene (TCE) is an occupational and environmental chemical that can cause severe hepatotoxicity. While our previous studies showed that the phosphatase inhibitor SET is a key mediator of TCE-induced liver cell apoptosis, the molecular mechanisms remain elusive. Using quantitative phosphoproteomic analysis, we report here that nucleolin is a SET-regulated phosphoprotein in human liver HL-7702 cells. Functional analysis suggested that SET promoted dephosphorylation of nucleolin, decreased its binding to its transcriptional activator, c-myc, and upregulated nucleolin expression in TCE-treated cells. Importantly, TCE-induced hepatocyte apoptosis was significantly attenuated when nucleolin was downregulated with specific siRNAs. These findings indicate that TCE may induce hepatocyte apoptosis via SET-mediated dephosphorylation and overexpression of nucleolin. PMID:28402964

SET mediates TCE-induced liver cell apoptosis through dephosphorylation and upregulation of nucleolin.

PubMed

Ren, Xiaohu; Huang, Xinfeng; Yang, Xifei; Liu, Yungang; Liu, Wei; Huang, Haiyan; Wu, Desheng; Zou, Fei; Liu, Jianjun

2017-06-20

Trichloroethylene (TCE) is an occupational and environmental chemical that can cause severe hepatotoxicity. While our previous studies showed that the phosphatase inhibitor SET is a key mediator of TCE-induced liver cell apoptosis, the molecular mechanisms remain elusive. Using quantitative phosphoproteomic analysis, we report here that nucleolin is a SET-regulated phosphoprotein in human liver HL-7702 cells. Functional analysis suggested that SET promoted dephosphorylation of nucleolin, decreased its binding to its transcriptional activator, c-myc, and upregulated nucleolin expression in TCE-treated cells. Importantly, TCE-induced hepatocyte apoptosis was significantly attenuated when nucleolin was downregulated with specific siRNAs. These findings indicate that TCE may induce hepatocyte apoptosis via SET-mediated dephosphorylation and overexpression of nucleolin.

Metagenomic and Metatranscriptomic Analyses Reveal the Structure and Dynamics of a Dechlorinating Community Containing Dehalococcoides mccartyi and Corrinoid-Providing Microorganisms under Cobalamin-Limited Conditions

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

Men, Yujie; Yu, Ke; Bælum, Jacob

ABSTRACT The aim of this study is to obtain a systems-level understanding of the interactions betweenDehalococcoidesand corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities, and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven putative draft genomes were binned from the metagenomes. At an early stage (2 days), more transcripts of genes in theVeillonellaceaebin-genome were detected in the metatranscriptome of the enrichment without exogenous cobalamin than in the one with the addition of cobalamin. Among these genes, sporulation-related genes exhibited the highest differential expression when cobalamin wasmore » not added, suggesting a possible release route of corrinoids from corrinoid producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoidde novobiosynthesis pathway was also assigned to theVeillonellaceaebin-genome. Targeted quantitative PCR (qPCR) analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin than in the enrichment with cobalamin. Furthermore, the corrinoid salvaging and modification pathway ofDehalococcoideswas upregulated in response to the cobalamin stress. This study provides important insights into the microbial interactions and roles played by members of dechlorinating communities under cobalamin-limited conditions. IMPORTANCEThe key chloroethene-dechlorinating bacteriumDehalococcoides mccartyiis a cobalamin auxotroph, thus acquiring corrinoids from other community members. Therefore, it is important to investigate the microbe-microbe interactions betweenDehalococcoidesand the corrinoid-providing microorganisms in a community. This study provides systems

Test of aerobic TCE degradation by willows (Salix viminalis) and willows inoculated with TCE-cometabolizing strains of Burkholderia cepacia.

PubMed

Clausen, Lauge Peter Westergaard; Broholm, Mette Martina; Gosewinkel, Ulrich; Trapp, Stefan

2017-08-01

Trichloroethylene (TCE) is a widespread soil and groundwater pollutant and clean-up is often problematic and expensive. Phytoremediation may be a cost-effective solution at some sites. This study investigates TCE degradation by willows (S. viminalis) and willows inoculated with three strains of B. cepacia (301C, PR1-31 and VM1330-pTOM), using chloride formation as an indicator of dehalogenation. Willows were grown in non-sterile, hydroponic conditions for 3 weeks in chloride-free nutrient solution spiked with TCE. TCE was added weekly due to rapid loss by volatilization. Chloride and TCE in solution were measured every 2-3 days and chloride and metabolite concentrations in plants were measured at test termination. Based on transpiration, no tree toxicity of TCE exposure was observed. However, trees grown in chloride-free solution showed severely inhibited transpiration. No or very little chloride was formed during the test, and levels of chloride in TCE-exposed trees were not elevated. Chloride concentrations in chloride containing TCE-free nutrient solution doubled within 23 days, indicating active exclusion of chloride by root cell membranes. Only traces of TCE-metabolites were detected in plant tissue. We conclude that TCE is not, or to a limited extent (less than 3%), aerobically degraded by the willow trees. The three strains of B. cepacia did not enhance TCE mineralization. Future successful application of rhizo- and phytodegradation of TCE requires measures to be taken to improve the degradation rates.

Chloroethene degradation and expression of Dehalococcoides dehalogenase genes in cultures originating from Yangtze sediments.

PubMed

Kranzioch, Irene; Ganz, Selina; Tiehm, Andreas

2015-02-01

The anaerobic Dehalococcoides spp. is the only microorganism known to completely dechlorinate the hazardous compounds tetrachloroethene (PCE) or trichloroethene (TCE) via dichloroethene (DCE) and vinyl chloride (VC) to the terminal product, ethene. In this study, growth of Dehalococcoides spp. (DHC) and the expression of DHC dehalogenase genes were demonstrated for Yangtze enrichment cultures. Reductive dechlorination of chloroethenes occurred in Yangtze sediment without the addition of any external auxiliary substrates. All Yangtze enrichment cultures completely dechlorinated PCE and cis-DCE to ethene. To investigate expression of the dehalogenase genes pceA, tceA, vcrA, and bvcA, a protocol for messenger RNA (mRNA) extraction followed by reverse transcription and quantitative PCR analysis was established. During dechlorination, an increase in gene copy numbers of pceA, tceA, and vcrA was observed. However, temporary formation of mRNA was only measured in the case of the dehalogenase genes tceA and vcrA. Comparison of DHC dehalogenase patterns indicated that the Yangtze DHC community does not match any of the previously published enrichment cultures that were obtained from contaminated areas in the USA or Europe.

Metagenomic and Metatranscriptomic Analyses Reveal the Structure and Dynamics of a Dechlorinating Community Containing Dehalococcoides mccartyi and Corrinoid-Providing Microorganisms under Cobalamin-Limited Conditions

DOE PAGES

Men, Yujie; Yu, Ke; Bælum, Jacob; ...

2017-02-10

The aim of this paper is to obtain a systems-level understanding of the interactions between Dehalococcoides and corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities, and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven putative draft genomes were binned from the metagenomes. At an early stage (2 days), more transcripts of genes in the Veillonellaceae bin-genome were detected in the metatranscriptome of the enrichment without exogenous cobalamin than in the one with the addition of cobalamin. Among these genes, sporulation-related genes exhibited the highest differential expressionmore » when cobalamin was not added, suggesting a possible release route of corrinoids from corrinoid producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoid de novo biosynthesis pathway was also assigned to the Veillonellaceae bin-genome. Targeted quantitative PCR (qPCR) analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin than in the enrichment with cobalamin. Furthermore, the corrinoid salvaging and modification pathway of Dehalococcoides was upregulated in response to the cobalamin stress. Finally, this study provides important insights into the microbial interactions and roles played by members of dechlorinating communities under cobalamin-limited conditions.« less

Metagenomic and Metatranscriptomic Analyses Reveal the Structure and Dynamics of a Dechlorinating Community Containing Dehalococcoides mccartyi and Corrinoid-Providing Microorganisms under Cobalamin-Limited Conditions

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

Men, Yujie; Yu, Ke; Bælum, Jacob

The aim of this paper is to obtain a systems-level understanding of the interactions between Dehalococcoides and corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities, and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven putative draft genomes were binned from the metagenomes. At an early stage (2 days), more transcripts of genes in the Veillonellaceae bin-genome were detected in the metatranscriptome of the enrichment without exogenous cobalamin than in the one with the addition of cobalamin. Among these genes, sporulation-related genes exhibited the highest differential expressionmore » when cobalamin was not added, suggesting a possible release route of corrinoids from corrinoid producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoid de novo biosynthesis pathway was also assigned to the Veillonellaceae bin-genome. Targeted quantitative PCR (qPCR) analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin than in the enrichment with cobalamin. Furthermore, the corrinoid salvaging and modification pathway of Dehalococcoides was upregulated in response to the cobalamin stress. Finally, this study provides important insights into the microbial interactions and roles played by members of dechlorinating communities under cobalamin-limited conditions.« less

Chlorinated Electron Acceptor Abundance Drives Selection of Dehalococcoides mccartyi (D. mccartyi) Strains in Dechlorinating Enrichment Cultures and Groundwater Environments

PubMed Central

Pérez-de-Mora, Alfredo; Lacourt, Anna; McMaster, Michaye L.; Liang, Xiaoming; Dworatzek, Sandra M.; Edwards, Elizabeth A.

2018-01-01

Dehalococcoides mccartyi (D. mccartyi) strains differ primarily from one another by the number and identity of the reductive dehalogenase homologous catalytic subunit A (rdhA) genes within their respective genomes. While multiple rdhA genes have been sequenced, the activity of the corresponding proteins has been identified in only a few cases. Examples include the enzymes whose substrates are groundwater contaminants such as trichloroethene (TCE), cis-dichloroethene (cDCE) and vinyl chloride (VC). The associated rdhA genes, namely tceA, bvcA, and vcrA, along with the D. mccartyi 16S rRNA gene are often used as biomarkers of growth in field samples. In this study, we monitored an additional 12 uncharacterized rdhA sequences identified in the metagenome in the mixed D. mccartyi-containing culture KB-1 to monitor population shifts in more detail. Quantitative PCR (qPCR) assays were developed for 15 D. mccartyi rdhA genes and used to measure population diversity in 11 different sub-cultures of KB-1, each enriched on different chlorinated ethenes and ethanes. The proportion of rdhA gene copies relative to D. mccartyi 16S rRNA gene copies revealed the presence of multiple distinct D. mccartyi strains in each culture, many more than the two strains inferred from 16S rRNA analysis. The specific electron acceptor amended to each culture had a major influence on the distribution of D. mccartyi strains and their associated rdhA genes. We also surveyed the abundance of rdhA genes in samples from two bioaugmented field sites (Canada and United Kingdom). Growth of the dominant D. mccartyi strain in KB-1 was detected at the United Kingdom site. At both field sites, the measurement of relative rdhA abundances revealed D. mccartyi population shifts over time as dechlorination progressed from TCE through cDCE to VC and ethene. These shifts indicate a selective pressure of the most abundant chlorinated electron acceptor, as was also observed in lab cultures. These results also

Editor's Highlight: High-Throughput Functional Genomics Identifies Modulators of TCE Metabolite Genotoxicity and Candidate Susceptibility Genes.

PubMed

De La Rosa, Vanessa Y; Asfaha, Jonathan; Fasullo, Michael; Loguinov, Alex; Li, Peng; Moore, Lee E; Rothman, Nathaniel; Nakamura, Jun; Swenberg, James A; Scelo, Ghislaine; Zhang, Luoping; Smith, Martyn T; Vulpe, Chris D

2017-11-01

Trichloroethylene (TCE), an industrial chemical and environmental contaminant, is a human carcinogen. Reactive metabolites are implicated in renal carcinogenesis associated with TCE exposure, yet the toxicity mechanisms of these metabolites and their contribution to cancer and other adverse effects remain unclear. We employed an integrated functional genomics approach that combined functional profiling studies in yeast and avian DT40 cell models to provide new insights into the specific mechanisms contributing to toxicity associated with TCE metabolites. Genome-wide profiling studies in yeast identified the error-prone translesion synthesis (TLS) pathway as an import mechanism in response to TCE metabolites. The role of TLS DNA repair was further confirmed by functional profiling in DT40 avian cell lines, but also revealed that TLS and homologous recombination DNA repair likely play competing roles in cellular susceptibility to TCE metabolites in higher eukaryotes. These DNA repair pathways are highly conserved between yeast, DT40, and humans. We propose that in humans, mutagenic TLS is favored over homologous recombination repair in response to TCE metabolites. The results of these studies contribute to the body of evidence supporting a mutagenic mode of action for TCE-induced renal carcinogenesis mediated by reactive metabolites in humans. Our approach illustrates the potential for high-throughput in vitro functional profiling in yeast to elucidate toxicity pathways (molecular initiating events, key events) and candidate susceptibility genes for focused study. © The Author 2017. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Bacteria of an anaerobic 1,2-dichloropropane-dechlorinating mixed culture are phylogenetically related to those of other anaerobic dechlorinating consortia.

PubMed

Schlötelburg, C; von Wintzingerode, F; Hauck, R; Hegemann, W; Göbel, U B

2000-07-01

A 16S-rDNA-based molecular study was performed to determine the bacterial diversity of an anaerobic, 1,2-dichloropropane-dechlorinating bioreactor consortium derived from sediment of the River Saale, Germany. Total community DNA was extracted and bacterial 16S rRNA genes were subsequently amplified using conserved primers. A clone library was constructed and analysed by sequencing the 16S rDNA inserts of randomly chosen clones followed by dot blot hybridization with labelled polynucleotide probes. The phylogenetic analysis revealed significant sequence similarities of several as yet uncultured bacterial species in the bioreactor to those found in other reductively dechlorinating freshwater consortia. In contrast, no close relationship was obtained with as yet uncultured bacteria found in reductively dechlorinating consortia derived from marine habitats. One rDNA clone showed >97% sequence similarity to Dehalobacter species, known for reductive dechlorination of tri- and tetrachloroethene. These results suggest that reductive dechlorination in microbial freshwater habitats depends upon a specific bacterial community structure.

Metagenomic and Metatranscriptomic Analyses Reveal the Structure and Dynamics of a Dechlorinating Community Containing Dehalococcoides mccartyi and Corrinoid-Providing Microorganisms under Cobalamin-Limited Conditions

PubMed Central

Yu, Ke; Bælum, Jacob; Gao, Ying; Tremblay, Julien; Prestat, Emmanuel; Stenuit, Ben; Tringe, Susannah G.; Jansson, Janet; Zhang, Tong; Alvarez-Cohen, Lisa

2017-01-01

ABSTRACT The aim of this study is to obtain a systems-level understanding of the interactions between Dehalococcoides and corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities, and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven putative draft genomes were binned from the metagenomes. At an early stage (2 days), more transcripts of genes in the Veillonellaceae bin-genome were detected in the metatranscriptome of the enrichment without exogenous cobalamin than in the one with the addition of cobalamin. Among these genes, sporulation-related genes exhibited the highest differential expression when cobalamin was not added, suggesting a possible release route of corrinoids from corrinoid producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoid de novo biosynthesis pathway was also assigned to the Veillonellaceae bin-genome. Targeted quantitative PCR (qPCR) analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin than in the enrichment with cobalamin. Furthermore, the corrinoid salvaging and modification pathway of Dehalococcoides was upregulated in response to the cobalamin stress. This study provides important insights into the microbial interactions and roles played by members of dechlorinating communities under cobalamin-limited conditions. IMPORTANCE The key chloroethene-dechlorinating bacterium Dehalococcoides mccartyi is a cobalamin auxotroph, thus acquiring corrinoids from other community members. Therefore, it is important to investigate the microbe-microbe interactions between Dehalococcoides and the corrinoid-providing microorganisms in a community. This study provides

Biodegradation of trichloroethylene (TCE) by methanotrophic community.

PubMed

Shukla, Awadhesh K; Vishwakarma, Pranjali; Upadhyay, S N; Tripathi, Anil K; Prasana, H C; Dubey, Suresh K

2009-05-01

Laboratory incubation experiments were carried out to assess the potential of methanotrophic culture for degrading TCE. Measurements of the growth rate and TCE degradation showed that the methanotrophs not only grew in presence of TCE but also degraded TCE. The rate of TCE degradation was found to be 0.19 ppm h(-1). The reverse transcriptase-PCR test was conducted to quantify expression of pmoA and mmoX genes. RT-PCR revealed expression of pmoA gene only. This observation provides evidence that the pmoA gene was functionally active for pMMO enzyme during the study. The diversity of the methanotrophs involved in TCE degradation was assessed by PCR amplification, cloning, restriction fragment length polymorphism and phylogenetic analysis of pmoA genes. Results suggested the occurrence of nine different phylotypes belonging to Type II methanotrophs in the enriched cultures. Out of the nine, five clustered with, genera Methylocystis and rest got clustered in to a separate group.

[Steam and air co-injection in removing TCE in 2D-sand box].

PubMed

Wang, Ning; Peng, Sheng; Chen, Jia-Jun

2014-07-01

Steam and air co-injection is a newly developed and promising soil remediation technique for non-aqueous phase liquids (NAPLs) in vadose zone. In this study, in order to investigate the mechanism of the remediation process, trichloroethylene (TCE) removal using steam and air co-injection was carried out in a 2-dimensional sandbox with different layered sand structures. The results showed that co-injection perfectly improved the "tailing" effect compared to soil vapor extraction (SVE), and the remediation process of steam and air co-injection could be divided into SVE stage, steam strengthening stage and heat penetration stage. Removal ratio of the experiment with scattered contaminant area was higher and removal speed was faster. The removal ratios from the two experiments were 93.5% and 88.2%, and the removal periods were 83.9 min and 90.6 min, respectively. Steam strengthened the heat penetration stage. The temperature transition region was wider in the scattered NAPLs distribution experiment, which reduced the accumulation of TCE. Slight downward movement of TCE was observed in the experiment with TCE initially distributed in a fine sand zone. And such downward movement of TCE reduced the TCE removal ratio.

Bacteria associated with oak and ash on a TCE-contaminated site: characterization of isolates with potential to avoid evapotranspiration of TCE.

PubMed

Weyens, Nele; Taghavi, Safiyh; Barac, Tanja; van der Lelie, Daniel; Boulet, Jana; Artois, Tom; Carleer, Robert; Vangronsveld, Jaco

2009-11-01

Along transects under a mixed woodland of English Oak (Quercus robur) and Common Ash (Fraxinus excelsior) growing on a trichloroethylene (TCE)-contaminated groundwater plume, sharp decreases in TCE concentrations were observed, while transects outside the planted area did not show this remarkable decrease. This suggested a possibly active role of the trees and their associated bacteria in the remediation process. Therefore, the cultivable bacterial communities associated with both tree species growing on this TCE-contaminated groundwater plume were investigated in order to assess the possibilities and practical aspects of using these common native tree species and their associated bacteria for phytoremediation. In this study, only the cultivable bacteria were characterized because the final aim was to isolate TCE-degrading, heavy metal resistant bacteria that might be used as traceable inocula to enhance bioremediation. Cultivable bacteria isolated from bulk soil, rhizosphere, root, stem, and leaf were genotypically characterized by amplified rDNA restriction analysis (ARDRA) of their 16S rRNA gene and identified by 16S rRNA gene sequencing. Bacteria that displayed distinct ARDRA patterns were screened for heavy metal resistance, as well as TCE tolerance and degradation, as preparation for possible future in situ inoculation experiments. Furthermore, in situ evapotranspiration measurements were performed to investigate if the degradation capacity of the associated bacteria is enough to prevent TCE evapotranspiration to the air. Between both tree species, the associated populations of cultivable bacteria clearly differed in composition. In English Oak, more species-specific, most likely obligate endophytes were found. The majority of the isolated bacteria showed increased tolerance to TCE, and TCE degradation capacity was observed in some of the strains. However, in situ evapotranspiration measurements revealed that a significant amount of TCE and its metabolites

Bacteria associated with oak and ash on a TCE-contaminated site: Characterization of isolates with potential to avoid evapotranspiration of TCE

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

Weyens, N.; van der Lelie, D.; Taghavi, S.

2009-11-01

Along transects under a mixed woodland of English Oak (Quercus robur) and Common Ash (Fraxinus excelsior) growing on a trichloroethylene (TCE)-contaminated groundwater plume, sharp decreases in TCE concentrations were observed, while transects outside the planted area did not show this remarkable decrease. This suggested a possibly active role of the trees and their associated bacteria in the remediation process. Therefore, the cultivable bacterial communities associated with both tree species growing on this TCE-contaminated groundwater plume were investigated in order to assess the possibilities and practical aspects of using these common native tree species and their associated bacteria for phytoremediation. Inmore » this study, only the cultivable bacteria were characterized because the final aim was to isolate TCE-degrading, heavy metal resistant bacteria that might be used as traceable inocula to enhance bioremediation. Cultivable bacteria isolated from bulk soil, rhizosphere, root, stem, and leaf were genotypically characterized by amplified rDNA restriction analysis (ARDRA) of their 16S rRNA gene and identified by 16S rRNA gene sequencing. Bacteria that displayed distinct ARDRA patterns were screened for heavy metal resistance, as well as TCE tolerance and degradation, as preparation for possible future in situ inoculation experiments. Furthermore, in situ evapotranspiration measurements were performed to investigate if the degradation capacity of the associated bacteria is enough to prevent TCE evapotranspiration to the air. Between both tree species, the associated populations of cultivable bacteria clearly differed in composition. In English Oak, more species-specific, most likely obligate endophytes were found. The majority of the isolated bacteria showed increased tolerance to TCE, and TCE degradation capacity was observed in some of the strains. However, in situ evapotranspiration measurements revealed that a significant amount of TCE and its

Effects of Potassium Permanganate Oxidation on Subsurface Microbial Activity

NASA Technical Reports Server (NTRS)

Rowland, Martin A.; Brubaker, Gaylen R.; Westray, Mark; Morris, Damon; Kohler, Keisha; McCool, Alex (Technical Monitor)

2001-01-01

In situ chemical oxidation has the potential for degrading large quantities of organic contaminants and can be more effective and timely than traditional ex situ treatment methods. However, there is a need to better characterize the potential effects of this treatment on natural processes. This study focuses on potential inhibition to anaerobic dechlorination of trichloroethene (TCE) in soils from a large manufacturing facility as a result of in situ oxidation using potassium permanganate (KMn04)Previous microcosm studies established that natural attenuation occurs on-site and that it is enhanced by the addition of ethanol to the system. A potential remediation scheme for the site involves the use of potassium permanganate to reduce levels of TCE in heavily contaminated areas, then to inject ethanol into the system to "neutralize" excess oxidant and enhance microbial degradation. However, it is currently unknown whether the exposure of indigenous microbial populations to potassium permanganate may adversely affect biological reductive dechlorination by these microorganisms. Consequently, additional microcosm studies were conducted to evaluate this remediation scheme and assess the effect of potassium permanganate addition on biological reductive dechlorination of TCE. Samples of subsurface soil and groundwater were collected from a TCE-impacted area of the site. A portion of the soil was pretreated with nutrients and ethanol to stimulate microbial activity, while the remainder of the soil was left unamended. Soil/groundwater microcosms were prepared in sealed vials using the nutrient-amended and unamended soils, and the effects of potassium permanganate addition were evaluated using two permanganate concentrations (0.8 and 2.4 percent) and two contact times (1 and 3 weeks). TCE was then re-added to each microcosm and TCE and dichloroethene (DCE) concentrations were monitored to determine the degree to which microbial dechlorination occurred following chemical

Model Parameter Variability for Enhanced Anaerobic Bioremediation of DNAPL Source Zones

NASA Astrophysics Data System (ADS)

Mao, X.; Gerhard, J. I.; Barry, D. A.

2005-12-01

The objective of the Source Area Bioremediation (SABRE) project, an international collaboration of twelve companies, two government agencies and three research institutions, is to evaluate the performance of enhanced anaerobic bioremediation for the treatment of chlorinated ethene source areas containing dense, non-aqueous phase liquids (DNAPL). This 4-year, 5.7 million dollars research effort focuses on a pilot-scale demonstration of enhanced bioremediation at a trichloroethene (TCE) DNAPL field site in the United Kingdom, and includes a significant program of laboratory and modelling studies. Prior to field implementation, a large-scale, multi-laboratory microcosm study was performed to determine the optimal system properties to support dehalogenation of TCE in site soil and groundwater. This statistically-based suite of experiments measured the influence of key variables (electron donor, nutrient addition, bioaugmentation, TCE concentration and sulphate concentration) in promoting the reductive dechlorination of TCE to ethene. As well, a comprehensive biogeochemical numerical model was developed for simulating the anaerobic dehalogenation of chlorinated ethenes. An appropriate (reduced) version of this model was combined with a parameter estimation method based on fitting of the experimental results. Each of over 150 individual microcosm calibrations involved matching predicted and observed time-varying concentrations of all chlorinated compounds. This study focuses on an analysis of this suite of fitted model parameter values. This includes determining the statistical correlation between parameters typically employed in standard Michaelis-Menten type rate descriptions (e.g., maximum dechlorination rates, half-saturation constants) and the key experimental variables. The analysis provides insight into the degree to which aqueous phase TCE and cis-DCE inhibit dechlorination of less-chlorinated compounds. Overall, this work provides a database of the numerical

ELECTROCHEMICAL DECHLORINATION OF 2-CHLOROBIPHENYL IN AQUEOUS SOLUTION

EPA Science Inventory

This paper presents electrochemical dechlorination of 2-chlorobiphenyl (2-Cl BP) in aqueous environment using palladium modified granular graphite electrodes. 2-Cl BP, the PCB congener that requires the highest reduction potential, was effectively dechlorinated in electrochemical...

Dechlorination and Decolorization of Organics in Bleach Plant E-1 Effluent by Photochemical Processes

NASA Astrophysics Data System (ADS)

Xie, Tianyan

1994-01-01

Photochemical study of the dechlorination of four model compounds, 4,5-dichloroguaiacol, 2,4,6-trichlorophenol, 2,3,4,5-tetrachlorophenol, and tetrachloroguaiacol in aqueous solutions under UV radiation was conducted using ArF (193 nm) and KrF (248 nm) excimer laser to explore the response of chlorinated phenolics present in the E_1 effluent from conventional chlorine bleaching of softwood kraft pulp towards photo-oxidation processes. Kinetic study show that the overall dechlorination reaction follow the first order rate law. The factors affecting the dechlorination were investigated. The quantum yield of chloride ion formation was found to be dependent on pH of the reaction mixture, and orignal chlorine content of the compounds. The effect of the substituents on the aromatic ring on the reactivity of the compounds was studied. The mechanism for the dechlorination was proposed involving homolytic photo-dissociation, heterolytic cleavage of carbon-chlorine bonds and substitution reactions of hydroxyl radicals. It was found that the dechlorination under formation to chloride is influenced by the amount of organically bound chlorine in the starting material. Dechlorination reaction favors high pH. Guaiacols more easily undergo dechlorination than phenols. Four fractions of high relative molecular-mass chloro-organics or polychlorinated oxylignin (PCOL) were isolated from an E_1 effluent by combination of ultrafiltration, and purified by repeated precipitation. The fractions were analysed by classical functional group analysis and spectrophotometric methods. The analytical data indicated that the major structural differences between PCOL fractions and kraft lignin preparations are with regard to the content of founctional groups such as carboxyl content, methoxyl and hydroxyl contents. In addition, IR, ^1H and ^{13 }C NMR spectral analyses revealed an almost complete absence of absorption attributable to aromatic structures in PCOLs. These results and others led to the

Characteristics of permanganate oxidation of TCE at low reagent concentrations.

PubMed

Woo, N C; Hyun, S G; Park, W W; Lee, E S; Schwartz, F W

2009-12-01

A controlled-release technique using potassium permanganate (KMnO4) has been recently developed as a long-term and semi-passive remediation scheme for dilute groundwater plumes of chlorinated solvents such as trichloroethylene (TCE) and perchloroethylene. Batch experiments were performed to evaluate TCE removal efficiencies of a low concentration of permanganate (MnO4-) solution and to estimate the optimum dose of permanganate required to remove low levels of TCE from groundwater plumes without leaving intermediate organic forms. Experimental results indicated that when the molar ratio of [MnO4-]0/[TCE]0 was about 10, 95% of the TCE in the plume was removed within less than 90 min, and about 90% of the chloride in the organic forms was converted into inorganic ions, while the TCE removal rates and the chloride conversion rates were considerably lower when the [TCE]0/ [MnO4-]0 values were lower. These data suggested that the [MnO4-]0 and the [MnO4-]0/[TCE]0 values would have strong effects on the efficiency and completeness of TCE oxidation. Further detailed investigations of the effect of [MnO4-]0 and [MnO4-]0/[TCE]0 values on the removal efficiencies and completeness of the TCE oxidation are warranted for successful application of the controlled-release KMnO4 technique in practice.

REMEDIATION OF SITES CONTAMINATED WITH TCE

EPA Science Inventory

Widespread use of trichloroethylene (TCE) in the U.S. has resulted in its frequent detection in soil and groundwater. TCE can become a health hazard after being processed in the human liver; or reductive dehalogenation in the environment may result in production of vinyl chloride...

Reductive dechlorination of chlorobenzenes in surfactant-amended sediment slurries

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

Van Hoof, P.L.; Jafvert, C.T.

1996-11-01

Microbial anaerobic dechlorination of hexachlorobenzene (HCB) was examined in sediment slurries amended with two classes of nonionic surfactant, polyoxyethylene (POE) sorbitan fatty acid esters (Tweens) and POE alcohols (Brijs). The rationale for surfactant addition was to increase the bioavailability of highly sorbed organic pollutants to degrading microorganisms by enhancing their solubility. The solubility of HCB was initially enhanced via micellar partitioning; however, primary degradation of most surfactants occurred within 10 d. Dechlorination activity was significantly reduced at POE alcohol concentrations above the critical micelle concentration (cmc), with or without the occurrence of surfactant degradation. Tween 80 decreased HCB dechlorination atmore » concentrations significantly above the cmc. At concentrations closer to the cmc, Tween 80 increased dechlorination rate constants four- to fivefold in acclimated slurries. Additions of Tween 80 at or below the cmc stimulated dechlorination activity in unacclimated slurries that exhibited very little activity in unamended controls. An average of 89% of HCB was dechlorinated after 90 d, compared to 20% in unamended sediments. No effect was observed for POE alcohols at these sub-cmc levels. The lack of a stimulated response for the POE alcohols suggests that Tween 80 may not be acting simply as a source of carbon or energy.« less

Biosupported Bimetallic Pd Au Nanocatalysts for Dechlorination of Environmental Contaminants

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

De Corte, S.; Fitts, J.; Hennebel, T.

2011-08-30

Biologically produced monometallic palladium nanoparticles (bio-Pd) have been shown to catalyze the dehalogenation of environmental contaminants, but fail to efficiently catalyze the degradation of other important recalcitrant halogenated compounds. This study represents the first report of biologically produced bimetallic Pd/Au nanoparticle catalysts. The obtained catalysts were tested for the dechlorination of diclofenac and trichloroethylene. When aqueous bivalent Pd(II) and trivalent Au(III) ions were both added to concentrations of 50 mg L{sup -1} and reduced simultaneously by Shewanella oneidensis in the presence of H{sub 2}, the resulting cell-associated bimetallic nanoparticles (bio-Pd/Au) were able to dehalogenate 78% of the initially added diclofenacmore » after 24 h; in comparison, no dehalogenation was observed using monometallic bio-Pd or bio-Au. Other catalyst-synthesis strategies did not show improved dehalogenation of TCE and diclofenac compared with bio-Pd. Synchrotron-based X-ray diffraction, (scanning) transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the simultaneous reduction of Pd and Au supported on cells of S. oneidensis resulted in the formation of a unique bimetallic crystalline structure. This study demonstrates that the catalytic activity and functionality of possibly environmentally more benign biosupported Pd-catalysts can be improved by coprecipitation with Au.« less

Biological removal of the xenobiotic trichloroethylene (TCE) through cometabolism in nitrifying systems.

PubMed

Kocamemi, B Alpaslan; Ceçen, F

2010-01-01

In the present study, cometabolic TCE degradation was evaluated using NH(4)-N as the growth-substrate. At initial TCE concentrations up to 845 microg/L, TCE degradation followed first-order kinetics. The increase in ammonium utilization rate favored the degradation of TCE. This ensured that biological transformation of TCE in nitrifying systems is accomplished through a cometabolic pathway by the catalysis of non-specific ammonia oxygenase enzyme of nitrifiers. The transformation yield (T(y)) of TCE, the amount of TCE degraded per unit mass of NH(4)-N, strongly depended on the initial NH(4)-N and TCE concentrations. In order to allow a rough estimation of TCE removal and nitrification at different influent TCE and NH(4)-N concentrations, a linear relationship was developed between 1/T(y) and the initial NH(4)-N/TCE ratio. The estimated T(y) values lead to the conclusion that nitrifying systems are promising candidates for biological removal of TCE through cometabolism.

Transpiration and metabolisation of TCE by willow plants - a pot experiment.

PubMed

Schöftner, Philipp; Watzinger, Andrea; Holzknecht, Philipp; Wimmer, Bernhard; Reichenauer, Thomas G

2016-01-01

Willows were grown in glass cylinders filled with compost above water-saturated quartz sand, to trace the fate of TCE in water and plant biomass. The experiment was repeated once with the same plants in two consecutive years. TCE was added in nominal concentrations of 0, 144, 288, and 721 mg l(-1). Unplanted cylinders were set-up and spiked with nominal concentrations of 721 mg l(-1) TCE in the second year. Additionally, (13)C-enriched TCE solution (δ(13)C = 110.3 ‰) was used. Periodically, TCE content and metabolites were analyzed in water and plant biomass. The presence of TCE-degrading microorganisms was monitored via the measurement of the isotopic ratio of carbon ((13)C/(12)C) in TCE, and the abundance of (13)C-labeled microbial PLFAs (phospholipid fatty acids). More than 98% of TCE was lost via evapotranspiration from the planted pots within one month after adding TCE. Transpiration accounted to 94 to 78% of the total evapotranspiration loss. Almost 1% of TCE was metabolized in the shoots, whereby trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) were dominant metabolites; less trichloroethanol (TCOH) and TCE accumulated in plant tissues. Microbial degradation was ruled out by δ(13)C measurements of water and PLFAs. TCE had no detected influence on plant stress status as determined by chlorophyll-fluorescence and gas exchange.

Complete dechlorination of DDE/DDD using magnesium/palladium system.

PubMed

Gautam, Sumit Kumar; Suresh, Sumathi

2007-04-01

Kinetic studies on the dechlorination of 1,1-dichloro-2,2 bis (4,-chlorophenyl) ethane (DDD) and 1,1,dichloro-2,2 bis (4,-chlorophenyl) ethylene (DDE) in 0.05% biosurfactant revealed that the reaction follows second-order kinetics. The rate of reaction was dependent on the presence of acid, initial concentrations of the target compound, and zerovalent magnesium/tetravalent palladium. Gas chromatography-mass spectrometry analyses of DDE dechlorination revealed the formation of a completely dechlorinated hydrocarbon skeleton, with diphenylethane as the end product, thereby implying the removal of all four chlorine atoms of DDE. In the case of DDD, we identified two partially dechlorinated intermediates [namely, 1,1-dichloro-2, 2 bis (phenyl) ethane and 1, chloro-2, 2 bis (phenyl) ethane] and diphenylethane as the end product. On the basis of products formed from DDD dehalogenation, we propose the removal of aryl chlorine atoms as a first step. Our investigation reveals that biosurfactant may be an attractive solubilizing agent for DDT and its residues. The magnesium/palladium system is a promising option because of its high reactivity and ability to achieve complete dechlorination of DDE and DDD.

Microbial degradation of chloroethenes in groundwater systems

USGS Publications Warehouse

Bradley, Paul M.

2000-01-01

 The chloroethenes, tetrachloroethene (PCE) and trichloroethene (TCE) are among the most common contaminants detected in groundwater systems. As recently as 1980, the consensus was that chloroethene compounds were not significantly biodegradable in groundwater. Consequently, efforts to remediate chloroethene-contaminated groundwater were limited to largely unsuccessful pump-and-treat attempts. Subsequent investigation revealed that under reducing conditions, aquifer microorganisms can reductively dechlorinate PCE and TCE to the less chlorinated daughter products dichloroethene (DCE) and vinyl chloride (VC). Although recent laboratory studies conducted with halorespiring microorganisms suggest that complete reduction to ethene is possible, in the majority of groundwater systems reductive dechlorination apparently stops at DCE or VC. However, recent investigations conducted with aquifer and stream-bed sediments have demonstrated that microbial oxidation of these reduced daughter products can be significant under anaerobic redox conditions. The combination of reductive dechlorination of PCE and TCE under anaerobic conditions followed by anaerobic microbial oxidation of DCE and VC provides a possible microbial pathway for complete degradation of chloroethene contaminants in groundwater systems.

Microbial degradation of chloroethenes in groundwater systems

USGS Publications Warehouse

Bradley, P.M.

2000-01-01

The chloroethenes, tetrachloroethene (PCE) and trichloroethene (TCE) are among the most common contaminants detected in groundwater systems. As recently as 1980, the consensus was that chloroethene compounds were not significantly biodegradable in groundwater. Consequently, efforts to remediate chloroethene-contaminated groundwater were limited to largely unsuccessful pump-and-treat attempts. Subsequent investigation revealed that under reducing conditions, aquifer microorganisms can reductively dechlorinate PCE and TCE to the less chlorinated daughter products dichloroethene (DCE) and vinyl chloride (VC). Although recent laboratory studies conducted with halorespiring microorganisms suggest that complete reduction to ethene is possible, in the majority of groundwater systems reductive dechlorination apparently stops at DCE or VC. However, recent investigations conducted with aquifer and stream-bed sediments have demonstrated that microbial oxidation of these reduced daughter products can be significant under anaerobic redox conditions. The combination of reductive dechlorination of PCE and TCE under anaerobic conditions followed by anaerobic microbial oxidation of DCE and VC provides a possible microbial pathway for complete degradation of chloroethene contaminants in groundwater systems.

Nitrate reductase gene involvement in hexachlorobiphenyl dechlorination by Phanerochaete chrysosporium.

PubMed

De, Supriyo; Perkins, Michael; Dutta, Sisir K

2006-07-31

Polychlorobiphenyl (PCB) degradation usually occurs through reductive dechlorination under anaerobic conditions and phenolic ring cleavage under aerobic conditions. In this paper, we provide evidence of nitrate reductase (NaR) mediated dechlorination of hexachlorobiphenyl (PCB-153) in Phanerochaete chrysosporium under non-ligninolytic condition and the gene involved. The NaR enzyme and its cofactor, molybdenum (Mo), were found to mediate reductive dechlorination of PCBs even in aerobic condition. Tungsten (W), a competitive inhibitor of this enzyme, was found to suppress this dechlorination. Chlorine release assay provided further evidence of this nitrate reductase mediated dechlorination. Commercially available pure NaR enzyme from Aspergillus was used to confirm these results. Through homology search using TBLASTN program, NaR gene was identified, primers were designed and the RT-PCR product was sequenced. The NaR gene was then annotated in the P. chrysosporium genome (GenBank accession no. AY700576). This is the first report regarding the presence of nitrate reductase gene in this fungus with the explanation why this fungus can dechlorinate PCBs even in aerobic condition. These fungal inoculums are used commercially as pellets in sawdust for enhanced bioremediation of PCBs at the risk of depleting soil nitrates. Hence, the addition of nitrates to the pellets will reduce this risk as well as enhance its activity.

Cometabolic degradation kinetics of TCE and phenol by Pseudomonas putida.

PubMed

Chen, Yan-Min; Lin, Tsair-Fuh; Huang, Chih; Lin, Jui-Che

2008-08-01

Modeling of cometabolic kinetics is important for better understanding of degradation reaction and in situ application of bio-remediation. In this study, a model incorporated cell growth and decay, loss of transformation activity, competitive inhibition between growth substrate and non-growth substrate and self-inhibition of non-growth substrate was proposed to simulate the degradation kinetics of phenol and trichloroethylene (TCE) by Pseudomonas putida. All the intrinsic parameters employed in this study were measured independently, and were then used for predicting the batch experimental data. The model predictions conformed well to the observed data at different phenol and TCE concentrations. At low TCE concentrations (<2 mg l(-1)), the models with or without self-inhibition of non-growth substrate both simulated the experimental data well. However, at higher TCE concentrations (>6 mg l(-1)), only the model considering self-inhibition can describe the experimental data, suggesting that a self-inhibition of TCE was present in the system. The proposed model was also employed in predicting the experimental data conducted in a repeated batch reactor, and good agreements were observed between model predictions and experimental data. The results also indicated that the biomass loss in the degradation of TCE below 2 mg l(-1) can be totally recovered in the absence of TCE for the next cycle, and it could be used for the next batch experiment for the degradation of phenol and TCE. However, for higher concentration of TCE (>6 mg l(-1)), the recovery of biomass may not be as good as that at lower TCE concentrations.

Fate and Transport of TCE Solvents Through Saturated Karst Aquifer

NASA Astrophysics Data System (ADS)

Padilla, I. Y.; Carmona, M.; Anaya, A. A.

2014-12-01

Dense Nonaqueous-Phase Liquids (DNAPLs) are a group of organic compounds that have been a serious problem for groundwater pollution in karst. The industrial production and utilization of these chemicals spread since 1940, and are present at tens of thousands of contaminated sites worldwide. The physic-chemical properties of DNAPLs in conjunction with the hydraulic properties of the karst systems create the perfect condition for DNAPLs to penetrate the epikarst, reach the groundwater, and more within the karst system to zones of potential exposure, such as wells, streams and wetlands. Trichloroethylene (TCE) is the most common DNPAL found in the subsurface environment. This research studies the fate and transport of TCE DNAPL in a karstified limestone physical model (KLPM). Experiments are carried out in KLPM. The KLPM is an enclosed stainless steel tank packed with a rectangular limestone block (15cm x 15cm x 76cm) that simulates a saturated confine karst aquifer. DNAPL experiment involve the injection of 40 ml of pure TCE into steady groundwater flow at the upstream boundary of the KLPM model, while sampling spatially and temporally along the block. Samples are analyzed for TCE on the pure and dissolved phase. Pure TCE is analyzed volumetrically and dissolved phase concentrations are analyze using a High Performance Liquid Chromatography (HPLC). TCE data is used to construct temporal distributions curves (TDCs) at different spatial locations. Results show that pure TCE volumes are collected at the beginnings of the experiment in sampling ports located near the injection port and along preferential flow paths. TCE concentration TDCs show spatial variations related to the limestone block heterogeneously. Rapid response to TCE concentrations is associated with preferential flow paths. Slow response and long tailing of TCE of TCE concentration are associated with diffusive transport in rock matrix and mass transport rates limitations. Bimodal distributions are

Enhanced biotransformation of TCE using plant terpenoids in contaminated groundwater.

PubMed

Brown, J R-M; Thompson, I P; Paton, G I; Singer, A C

2009-12-01

To examine plant terpenoids as inducers of TCE (trichloroethylene) biotransformation by an indigenous microbial community originating from a plume of TCE-contaminated groundwater. One-litre microcosms of groundwater were spiked with 100 micromol 1(-1) of TCE and amended weekly for 16 weeks with 20 microl 1(-1) of the following plant monoterpenes: linalool, pulegone, R-(+) carvone, S-(-) carvone, farnesol, cumene. Yeast extract-amended and unamended control treatments were also prepared. The addition of R-carvone and S-carvone, linalool and cumene resulted in the biotransformation of upwards of 88% of the TCE, significantly more than the unamendment control (61%). The aforementioned group of terpenes also significantly (P < 0.05) allowed more TCE to be degraded than the remaining two terpenes (farnesol and pulegone), and the yeast extract treatment which biotransformed 74-75% of the TCE. The microbial community profile was monitored by denaturing gradient gel electrophoresis and demonstrated much greater similarities between the microbial communities in terpene-amended treatments than in the yeast extract or unamended controls. TCE biotransformation can be significantly enhanced through the addition of selected plant terpenoids. Plant terpenoid and nutrient supplementation to groundwater might provide an environmentally benign means of enhancing the rate of in situ TCE bioremediation.

Complete Reductive Dechlorination of 1,2-Dichloropropane by Anaerobic Bacteria

PubMed Central

Loffler, F. E.; Champine, J. E.; Ritalahti, K. M.; Sprague, S. J.; Tiedje, J. M.

1997-01-01

The transformation of 1,2-dichloropropane (1,2-D) was observed in anaerobic microcosms and enrichment cultures derived from Red Cedar Creek sediment. 1-Chloropropane (1-CP) and 2-CP were detected after an incubation period of 4 weeks. After 4 months the initial amount of 1,2-D was stoichiometrically converted to propene, which was not further transformed. Dechlorination of 1,2-D was not inhibited by 2-bromoethanesulfonate. Sequential 5% (vol/vol) transfers from active microcosms yielded a sediment-free, nonmethanogenic culture, which completely dechlorinated 1,2-D to propene at a rate of 5 nmol min(sup-1) mg of protein(sup-1). No intermediate formation of 1-CP or 2-CP was detected in the sediment-free enrichment culture. A variety of electron donors, including hydrogen, supported reductive dechlorination of 1,2-D. The highest dechlorination rates were observed between 20(deg) and 25(deg)C. In the presence of 1,2-D, the hydrogen threshold concentration was below 1 ppm by volume (ppmv). In addition to 1,2-D, the enrichment culture transformed 1,1-D, 2-bromo-1-CP, tetrachloroethene, 1,1,2,2-tetrachloroethane, and 1,2-dichloroethane to less halogenated compounds. These findings extend our knowledge of the reductive dechlorination process and show that halogenated propanes can be completely dechlorinated by anaerobic bacteria. PMID:16535654

Microbial polychlorinated biphenyl dechlorination in sediments by electrical stimulation: The effect of adding acetate and nonionic surfactant.

PubMed

Yu, Hui; Wan, Hui; Feng, Chunhua; Yi, Xiaoyun; Liu, Xiaoping; Ren, Yuan; Wei, Chaohai

2017-02-15

The necessity for developing an efficient and cost-effective in situ bioremediation technology for sediments contaminated with polychlorinated biphenyls (PCBs) has prompted the application of low-voltage electrical fields to anaerobic digestion systems. Here we show that the use of a sediment-based bio-electrochemical reactor (BER) poised at a potential of -0.50V (vs. a standard calomel electrode, SCE) substantially enhanced the reduction of 2,3,4,5-tetrachlorobiphenyl (PCB 61) when acetate was added as a carbon source. The addition of surfactant Tween 80 to the BER further accelerated the PCB 61 transformation. The comparative study of closed- and open-circuit reactors demonstrated the enrichment conditions affecting the bacterial community structure, the dominant dechlorination metabolisms, and thus the extent, the rate and the products of the reduction of PCBs. The dominant bacterial dechlorinators detected in the BERs in the presence of acetate and Tween 80 are Dehalogenimonas, Dehalobacter, Sulfuricurvum, Dechloromonas and Geobacter, which should be responsible for PCB dechlorination. This study improves understanding of the key factors influencing dechlorination activity in sediment-based BERs polarized at a low potential, as well as the metabolic mechanisms dominating in the PCB dechlorination process. Copyright © 2016 Elsevier B.V. All rights reserved.

Dechlorination of short chain chlorinated paraffins by nanoscale zero-valent iron.

PubMed

Zhang, Zhi-Yong; Lu, Mang; Zhang, Zhong-Zhi; Xiao, Meng; Zhang, Min

2012-12-01

In this study, nanoscale zero-valent iron (NZVI) particles were synthesized and used for the reductive dehalogenation of short chain chlorinated paraffins (SCCPs) in the laboratory. The results show that the dechlorination rate of chlorinated n-decane (CP(10)) by NZVI increased with decreased solution pH. Increasing the loading of NZVI enhanced the dechlorination rate of CP(10). With an increase in temperature, the degradation rate increased. The reduction of CP(10) by NZVI was accelerated with increasing the concentration of humic acid up to 15 mg/L but then was inhibited. The dechlorination of CP(10) within the initial 18 h followed pseudo-first order rate model. The formation of intermediate products indicates a stepwise dechlorination pathway of SCCPs by NZVI. The carbon chain length and chlorination degree of SCCPs have a polynominal impact on dechlorination reactions. Copyright © 2012 Elsevier B.V. All rights reserved.

SOURCES, EMISSION AND EXPOSURE TO TRICHLOROETHYLENE (TCE) AND RELATED CHEMICALS

EPA Science Inventory

This report documents the sources, emission, environmental fate and exposures for TCE, some of its metabolites, and some other chemicals known to produce identical metabolites. The major findings for TCE are:

1. The primary sources releasing TCE to the environment ...

2. The Physiological Opportunism of Desulfitobacterium hafniense Strain TCE1 towards Organohalide Respiration with Tetrachloroethene

   PubMed Central

   Duret, Aurélie; Holliger, Christof

   2012-01-01

   Desulfitobacterium hafniense strain TCE1 is capable of metabolically reducing tetra- and trichloroethenes by organohalide respiration. A previous study revealed that the pce gene cluster responsible for this process is located on an active composite transposon, Tn-Dha1. In the present work, we investigated the effects on the stability of the transposon during successive subcultivations of strain TCE1 in a medium depleted of tetrachloroethene. At the physiological level, an increased fitness of the population was observed after 9 successive transfers and was correlated with a decrease in the level of production of the PceA enzyme. The latter observation was a result of the gradual loss of the pce genes in the population of strain TCE1 and not of a regulation mechanism, as was postulated previously for a similar phenomenon described for Sulfurospirillum multivorans. A detailed molecular analysis of genetic rearrangements occurring around Tn-Dha1 showed two independent but concomitant events, namely, the transposition of the first insertion sequence, ISDha1-a, and homologous recombination across identical copies of ISDha1 flanking the transposon. A new model is proposed for the genetic heterogeneity around Tn-Dha1 in D. hafniense strain TCE1, along with some considerations for the cleavage mechanism mediated by the transposase TnpA1 encoded by ISDha1. PMID:22729540

3. DECHLORINATION ACTIVITY (CROSS-ACCLIMATION) OF FRESHWATER SEDIMENTS ADAPTED TO MONO- AND DI-CHLOROPHENOLS

   EPA Science Inventory

   The reductive dechlorination of chlorophenols (CPs) in sediment slurries (10% solids) adapted to dechlorinate mono- and di-CPs (DCP) was investigated to define the regiospecificity of the dechlorination reaction. nadapted sediment slurries amended with various ortho-substituted C...

4. Endophytic bacteria improve phytoremediation of Ni and TCE co-contamination.

   PubMed

   Weyens, Nele; Croes, Sarah; Dupae, Joke; Newman, Lee; van der Lelie, Daniel; Carleer, Robert; Vangronsveld, Jaco

   2010-07-01

   The aim of this work was to investigate if engineered endophytes can improve phytoremediation of co-contaminations by organic pollutants and toxic metals. As a model system, yellow lupine was inoculated with the endophyte Burkholderia cepacia VM1468 possessing (a) the pTOM-Bu61 plasmid, coding for constitutive trichloroethylene (TCE) degradation, and (b) the ncc-nre Ni resistance/sequestration system. Plants were exposed to Ni and TCE and (a) Ni and TCE phytotoxicity, (b) TCE degradation and evapotranspiration, and (c) Ni concentrations in the roots and shoots were determined. Inoculation with B. cepacia VM1468 resulted in decreased Ni and TCE phytotoxicity, as measured by 30% increased root biomass and up to 50% decreased activities of enzymes involved in anti-oxidative defence in the roots. In addition, TCE evapotranspiration showed a decreasing trend and a 5 times higher Ni uptake was observed after inoculation. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

5. Coexistence of two distinct Sulfurospirillum populations respiring tetrachloroethene-genomic and kinetic considerations.

   PubMed

   Buttet, Géraldine Florence; Murray, Alexandra Marie; Goris, Tobias; Burion, Mélissa; Jin, Biao; Rolle, Massimo; Holliger, Christof; Maillard, Julien

   2018-05-01

   Two anaerobic bacterial consortia, each harboring a distinct Sulfurospirillum population, were derived from a 10 year old consortium, SL2, previously characterized for the stepwise dechlorination of tetrachloroethene (PCE) to cis-dichloroethene (cis-DCE) via accumulation of trichloroethene (TCE). Population SL2-1 dechlorinated PCE to TCE exclusively, while SL2-2 produced cis-DCE from PCE without substantial TCE accumulation. The reasons explaining the long-term coexistence of the populations were investigated. Genome sequencing revealed a novel Sulfurospirillum species, designated 'Candidatus Sulfurospirillum diekertiae', whose genome differed significantly from other Sulfurospirillum spp. (78%-83% ANI). Genome-wise, SL2-1 and SL2-2 populations are almost identical, but differences in their tetrachloroethene reductive dehalogenase sequences explain the distinct dechlorination patterns. An extended series of batch cultures were performed at PCE concentrations of 2-200 μM. A model was developed to determine their dechlorination kinetic parameters. The affinity constant and maximal growth rate differ between the populations: the affinity is 6- to 8-fold higher and the growth rate 5-fold lower for SL2-1 than SL2-2. Mixed cultivation of the enriched populations at 6 and 30 μM PCE showed that a low PCE concentration could be the driving force for both functional diversity of reductive dehalogenases and niche specialization of organohalide-respiring bacteria with overlapping substrate ranges.

6. Reductive dechlorination of hexachlorobenzene to tri- and dichlorobenzenes in anaerobic sewage sludge.

   PubMed Central

   Fathepure, B Z; Tiedje, J M; Boyd, S A

   1988-01-01

   Hexachlorobenzene was dechlorinated to tri- and dichlorobenzenes in anaerobic sewage sludge. The complete biotransformation of 190 microM hexachlorobenzene (approximately 50 ppm) occurred within 3 weeks. The calculated rate of hexachlorobenzene dechlorination was 13.6 mumol liter-1 day-1. Hexachlorobenzene was dechlorinated via two routes, both involving the sequential removal of chlorine from the aromatic ring. The major route was hexachlorobenzene----pentachlorobenzene----1,2,3,5-tetrachlorobenzene--- -1,3,5- trichlorobenzene. Greater than 90% of the added hexachlorobenzene was recovered as 1,3,5-trichlorobenzene, and there was no evidence for further dechlorination of 1,3,5-trichlorobenzene. The minor route was hexachlorobenzene----pentachlorobenzene----1,2,4,5-tetrachlorobenzene--- -1,2,4- trichlorobenzene----dichlorobenzenes. These results extend reductive dechlorination to poorly water soluble aromatic hydrocarbons which could potentially include other important environmental pollutants like polychlorinated biphenyls. PMID:3355129

7. Effects of biochar on dechlorination of hexachlorobenzene and the bacterial community in paddy soil.

   PubMed

   Song, Yang; Bian, Yongrong; Wang, Fang; Herzberger, Anna; Yang, Xinglun; Gu, Chenggang; Jiang, Xin

   2017-11-01

   Anaerobic reductive dechlorination is an important degradation pathway for chlorinated organic contaminants in paddy soil. This study investigated the effects of amending paddy soil with wheat straw biochar on both the dechlorination of hexachlorobenzene (HCB), a typical highly chlorinated contaminant, and on the structure of soil bacteria communities. Soil amendment of 0.1% biochar did not significantly affect the dechlorination of HCB in the soil. However, biochar amendment at higher application levels (5%) stimulated the dechlorination of HCB in the first month of anaerobic incubation and inhibited the dechlorination of HCB after that period. The stimulation effect may be ascribed to the graphite carbon and carbon-centered persistent radicals, which are redox active, in biochar. The inhibiting effect could be partly ascribed to the reduced bioavailability of HCB in biochar-amended soils. High-throughput sequencing revealed that the amendment of biochar changed the soil bacterial community structure but not the bacterial abundances and diversities. The relative abundance of Dehalococcoidaceae in the tested soils showed a significant relationship with the dechlorination percentages of HCB, indicating that Dehalococcoidaceae may be the main HCB-dechlorinating bacteria in the studied paddy soil. The results indicated that low application levels of biochar did not affect the dechlorination of HCB in the paddy soil, while high application levels of biochar mainly inhibited the dechlorination of HCB due to the reduced bioavailability of HCB and the reduced abundances of certain dechlorinating bacteria in the biochar-amended paddy soil. Copyright © 2017 Elsevier Ltd. All rights reserved.

8. Contrasting dual (C, Cl) isotope fractionation offers potential to distinguish reductive chloroethene transformation from breakdown by permanganate.

   PubMed

   Doğan-Subaşı, Eylem; Elsner, Martin; Qiu, Shiran; Cretnik, Stefan; Atashgahi, Siavash; Shouakar-Stash, Orfan; Boon, Nico; Dejonghe, Winnie; Bastiaens, Leen

   2017-10-15

   cis-1,2-Dichloroethene (cis-DCE) and trichloroethene (TCE) are persistent, toxic and mobile pollutants in groundwater systems. They are both conducive to reductive dehalogenation and to oxidation by permanganate. In this study, the potential of dual element (C, Cl) compound specific isotope analyses (CSIA) for distinguishing between chemical oxidation and anaerobic reductive dechlorination of cis-DCE and TCE was investigated. Well-controlled cis-DCE degradation batch tests gave similar carbon isotope enrichment factors ε C (‰), but starkly contrasting dual element isotope slopes Δδ 13 C/Δδ 37 Cl for permanganate oxidation (ε C =-26‰±6‰, Δδ 13 C/Δδ 37 Cl≈-125±47) compared to reductive dechlorination (ε C =-18‰±4‰, Δδ 13 C/Δδ 37 Cl≈4.5±3.4). The difference can be tracked down to distinctly different chlorine isotope fractionation: an inverse isotope effect during chemical oxidation (ε Cl =+0.2‰±0.1‰) compared to a large normal isotope effect in reductive dechlorination (ε Cl =-3.3‰±0.9‰) (p≪0.05). A similar trend was observed for TCE. The dual isotope approach was evaluated in the field before and up to 443days after a pilot scale permanganate injection in the subsurface. Our study indicates, for the first time, the potential of the dual element isotope approach for distinguishing cis-DCE (and TCE) concentration drops caused by dilution, oxidation by permanganate and reductive dechlorination both at laboratory and field scale. Copyright © 2017. Published by Elsevier B.V.

9. Characterization of TCE DNAPL and Dissolved Phase Transport in Karst Media

   NASA Astrophysics Data System (ADS)

   Carmona, M.; Padilla, I. Y.

   2015-12-01

   Trichloroethylene (TCE) contaminated sites are a threat to the environment and human health. Of particular concerns is the contamination of karst groundwater systems (KGWSs). Their heterogeneous character, rapid flow through conduits, high permeability zones, and strong storage capacity in the rock porous-matrix pose a high risk of exposure over large areas and temporal scales. To achieve effective remedial actions for TCE removal, it is important to understand and quantify the fate and transport process of trichloroethylene in these systems. This research studies the fate, transport, and distribution of TCE Non-Aqueous Phase Liquids (NAPLs) and associated dissolved species in KGWSs. Experiments are conducted in a karstified limestone physical model, a limestone rock mimicking a saturated confined karst aquifer. After injecting TCE solvent into a steady groundwater flow field, samples are taken spatially and temporally and analyzed for TCE NAPL and dissolved phases. Data analysis shows the rapid detection of TCE NAPL and high aqueous concentrations along preferential pathway, even at distances far away from the injection point. Temporal distribution curves exhibit spatial variations related to the limestone rock heterogeneity. Rapid response to TCE concentrations is associated with preferential flow paths. Slow response with long tailing indicates rate-limited diffusive transport in the rock matrix. Overall, results indicate that karstified limestone has a high capacity to rapidly transport pure and dissolved TCE along preferential flow paths, and to store and slowly release TCE over long periods of time.

10. Endophytic bacteria improve phytoremediation of Ni and TCE co-contamination

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

    Weyens, N.; van der Lelie, D.; Croes, S.

    The aim of this work was to investigate if engineered endophytes can improve phytoremediation of co-contaminations by organic pollutants and toxic metals. As a model system, yellow lupine was inoculated with the endophyte Burkholderia cepacia VM1468 possessing (a) the pTOM-Bu61 plasmid, coding for constitutive trichloroethylene (TCE) degradation, and (b) the ncc-nre Ni resistance/sequestration system. Plants were exposed to Ni and TCE and (a) Ni and TCE phytotoxicity, (b) TCE degradation and evapotranspiration, and (c) Ni concentrations in the roots and shoots were determined. Inoculation with B. cepacia VM1468 resulted in decreased Ni and TCE phytotoxicity, as measured by 30% increasedmore » root biomass and up to 50% decreased activities of enzymes involved in anti-oxidative defence in the roots. In addition, TCE evapotranspiration showed a decreasing trend and a 5 times higher Ni uptake was observed after inoculation. Engineered endophytes can improve phytoremediation of mixed contaminations via enhanced degradation of organic contaminants and improved metal uptake and translocation.« less

11. Dechlorination of PCBs in the rhizosphere of Switchgrass and Poplar

    PubMed Central

    Meggo, Richard E.; Schnoor, Jerald L.; Hu, Dingfei

    2014-01-01

    Polychlorinated biphenyl (PCB) congeners (PCB 52, 77, and 153) singly and in mixture were spiked and aged in soil microcosms and subsequently planted with switchgrass (Panicum virgatum) or poplar (Populus deltoids x nigra DN34). The planted reactors showed significantly greater reductions in PCB parent compounds when compared to unplanted systems after 32 weeks. There was evidence of reductive dechlorination in both planted and unplanted systems, but the planted microcosms with fully developed roots and rhizospheres showed greater biotransformation than the unplanted reactors. These dechlorination products accounted for approximately all of the molar mass of parent compound lost. Based on the transformation products, reductive dechlorination pathways are proposed for rhizospheric biotransformation of PCB 52, 77, and 153. This is the first report of rhizosphere biotransformation pathways for reductive dechlorination in marginally aerobic, intermittently flooded soil as evidenced by a mass balance on transformation products. PMID:23603468

12. Aerobic TCE degradation by encapsulated toluene-oxidizing bacteria, Pseudomonas putida and Bacillus spp.

    PubMed

    Kim, Seungjin; Bae, Wookeun; Hwang, Jungmin; Park, Jaewoo

    2010-01-01

    The degradation rates of toluene and trichloroethylene (TCE) by Pseudomonas putida and Bacillus spp. that were encapsulated in polyethylene glycol (PEG) polymers were evaluated in comparison with the results of exposure to suspended cultures. PEG monomers were polymerized together with TCE-degrading microorganisms, such that the cells were encapsulated in and protected by the matrices of the PEG polymers. TCE concentrations were varied from 0.1 to 1.5 mg/L. In the suspended cultures of P. putida, the TCE removal rate decreased as the initial TCE concentration increased, revealing TCE toxicity or a limitation of reducing power, or both. When the cells were encapsulated, an initial lag period of about 10-20 h was observed for toluene degradation. Once acclimated, the encapsulated P. putida cultures were more tolerant to TCE at an experimental range of 0.6-1.0 mg/L and gave higher transfer efficiencies (mass TCE transformed/mass toluene utilized). When the TCE concentration was low (e.g., 0.1 mg/L) the removal of TCE per unit mass of cells (specific removal) was significantly lower, probably due to a diffusion limitation into the PEG pellet. Encapsulated Bacillus spp. were able to degrade TCE cometabolically. The encapsulated Bacillus spp. gave significantly higher values than did P. putida in the specific removal and the transfer efficiency, particularly at relatively high TCE concentration of approximately 1.0±0.5 mg/L. The transfer efficiency by encapsulated Bacillus spp. in this study was 0.27 mgTCE/mgToluene, which was one to two orders of magnitude greater than the reported values.

13. Surfactant-enhanced remediation of a trichloroethene-contaminated aquifer. 2. Transport of TCE

    USGS Publications Warehouse

    Sahoo, D.; Smith, J.A.; Imbrigiotta, T.E.; Mclellan, H.M.

    1998-01-01

    Field studies were conducted under an induced gradient in a trichloroethene (TCE)-contaminated aquifer at Picatinny Arsenal, NJ, to study (a) the rate-limited desorption of TCE from aquifer sediments to water and (b) the effect of a surfactant (Triton X-100) on the desorption and transport of TCE. Clean water was injected into the contaminated aquifer for 206 day. Triton X-100 was added for a 36-day period (days 36-71 from the start of clean water injection). The effect of Triton X-100 on the desorption and transport of TCE in the field was examined by observing the concentrations of these two solutes in four monitoring wells 3-9 m from the injection wells. These data show a small but discernible increase in the TCE concentration in two of the wells corresponding approximately to the time when surfactant reaches the wells; in the other two monitoring wells, the increase in TCE concentration is negligible. A solute transport model that assumes local sorption equilibrium and used a laboratory-derived distribution coefficient could not adequately describe TCE desorption and transport observed in the aquifer. Two model formulations that accounted for rate-limited sorption - two-site and multisite models - fit the data well. TCE concentrations after surfactant injection were underpredicted by the models unless mass transfer rate was increased to account for the effect of surfactant on the rate of TCE desorption. The concentration data from the two wells and the model analysis suggest that the rate of TCE desorption is increased (by approximately 30%) as a result of Triton X-100 injection.Field studies were conducted under an induced gradient in a trichloroethene (TCE)-contaminated aquifer at Picatinny Arsenal, NJ, to study (a) the rate-limited desorption of TCE from aquifer sediments to water and (b) the effect of a surfactant (Triton X-100) on the desorption and transport of TCE. Clean water was injected into the contaminated aquifer for 206 day. Triton X-100 was added

14. Degradation of trichloroethene with a noval ball milled Fe-C nanocomposite

    DOE PAGES

    Gao, Jie; Wang, Wei; Rondinone, Adam Justin; ...

    2015-07-18

    Nanoscale zero-valent iron (NZVI) is effective in reductively degrading dense non-aqueous phase liquids (DNAPLs), such as trichloroethene (TCE), in groundwater (i.e., dechlorination) although the NZVI technology itself still suffers from high material costs and inability to target hydrophobic contaminants in source zones. To address these problems, we developed a novel, inexpensive iron-carbon (Fe-C) nanocomposite material by simultaneously milling micron-size iron and activated carbon powder. Microscopic and X-ray diffraction (XRD) characterization of the composite material revealed that nanoparticles of Fe were dispersed in activated carbon and a new iron carbide phase was formed. Bench-scale studies showed that this material instantaneously sorbedmore » >90% of TCE from aqueous solutions and subsequently decomposed TCE into non-chlorinated products. Compared to milled Fe, Fe-C nanocomposite dechlorinated TCE at a slightly slower rate and favored the production of ethene over other TCE degradation products such as C 3-C 6 compounds. When placed in hexane-water mixture, the Fe-C nanocomposite materials are preferentially partitioned into the organic phase, indicating the ability of the composite materials to target DNAPL during remediation.« less

15. The Drosophila Translational Control Element (TCE) Is Required for High-Level Transcription of Many Genes That Are Specifically Expressed in Testes

    PubMed Central

    Anderson, Ashley K.; Ohler, Uwe; Wassarman, David A.

    2012-01-01

    To investigate the importance of core promoter elements for tissue-specific transcription of RNA polymerase II genes, we examined testis-specific transcription in Drosophila melanogaster. Bioinformatic analyses of core promoter sequences from 190 genes that are specifically expressed in testes identified a 10 bp A/T-rich motif that is identical to the translational control element (TCE). The TCE functions in the 5′ untranslated region of Mst(3)CGP mRNAs to repress translation, and it also functions in a heterologous gene to regulate transcription. We found that among genes with focused initiation patterns, the TCE is significantly enriched in core promoters of genes that are specifically expressed in testes but not in core promoters of genes that are specifically expressed in other tissues. The TCE is variably located in core promoters and is conserved in melanogaster subgroup species, but conservation dramatically drops in more distant species. In transgenic flies, short (300–400 bp) genomic regions containing a TCE directed testis-specific transcription of a reporter gene. Mutation of the TCE significantly reduced but did not abolish reporter gene transcription indicating that the TCE is important but not essential for transcription activation. Finally, mutation of testis-specific TFIID (tTFIID) subunits significantly reduced the transcription of a subset of endogenous TCE-containing but not TCE-lacking genes, suggesting that tTFIID activity is limited to TCE-containing genes but that tTFIID is not an obligatory regulator of TCE-containing genes. Thus, the TCE is a core promoter element in a subset of genes that are specifically expressed in testes. Furthermore, the TCE regulates transcription in the context of short genomic regions, from variable locations in the core promoter, and both dependently and independently of tTFIID. These findings set the stage for determining the mechanism by which the TCE regulates testis-specific transcription and understanding

16. The Drosophila Translational Control Element (TCE) is required for high-level transcription of many genes that are specifically expressed in testes.

    PubMed

    Katzenberger, Rebeccah J; Rach, Elizabeth A; Anderson, Ashley K; Ohler, Uwe; Wassarman, David A

    2012-01-01

    To investigate the importance of core promoter elements for tissue-specific transcription of RNA polymerase II genes, we examined testis-specific transcription in Drosophila melanogaster. Bioinformatic analyses of core promoter sequences from 190 genes that are specifically expressed in testes identified a 10 bp A/T-rich motif that is identical to the translational control element (TCE). The TCE functions in the 5' untranslated region of Mst(3)CGP mRNAs to repress translation, and it also functions in a heterologous gene to regulate transcription. We found that among genes with focused initiation patterns, the TCE is significantly enriched in core promoters of genes that are specifically expressed in testes but not in core promoters of genes that are specifically expressed in other tissues. The TCE is variably located in core promoters and is conserved in melanogaster subgroup species, but conservation dramatically drops in more distant species. In transgenic flies, short (300-400 bp) genomic regions containing a TCE directed testis-specific transcription of a reporter gene. Mutation of the TCE significantly reduced but did not abolish reporter gene transcription indicating that the TCE is important but not essential for transcription activation. Finally, mutation of testis-specific TFIID (tTFIID) subunits significantly reduced the transcription of a subset of endogenous TCE-containing but not TCE-lacking genes, suggesting that tTFIID activity is limited to TCE-containing genes but that tTFIID is not an obligatory regulator of TCE-containing genes. Thus, the TCE is a core promoter element in a subset of genes that are specifically expressed in testes. Furthermore, the TCE regulates transcription in the context of short genomic regions, from variable locations in the core promoter, and both dependently and independently of tTFIID. These findings set the stage for determining the mechanism by which the TCE regulates testis-specific transcription and understanding the

17. Regiospecific dechlorination of pentachlorophenol by dichlorophenol-adapted microorganisms in freshwater, anaerobic sediment slurries.

    PubMed Central

    Bryant, F O; Hale, D D; Rogers, J E

    1991-01-01

    The reductive dechlorination of pentachlorophenol (PCP) was investigated in anaerobic sediments that contained nonadapted or 2,4- or 3,4-dichlorophenol (DCP)-adapted microbial communities. Adaptation of sediment communities increased the rate of conversion of 2,4- or 3,4-DCP to monochlorophenols (CPs) and eliminated the lag phase before dechlorination was observed. Both 2,4- and 3,4-DCP-adapted sediment communities dechlorinated the six DCP isomers to CPs. The specificity of chlorine removal from the DCP isomers indicated a preference for ortho-chlorine removal by 2,4-DCP-adapted sediment communities and for para-chlorine removal by 3,4-DCP-adapted sediment communities. Sediment slurries containing nonadapted microbial communities either did not dechlorinate PCP or did so following a lag phase of at least 40 days. Sediment communities adapted to dechlorinate 2,4- or 3,4-DCP dechlorinated PCP without an initial lag phase. The 2,4-DCP-adapted communities initially removed the ortho-chlorine from PCP, whereas the 3,4-DCP-adapted communities initially removed the para-chlorine from PCP. A 1:1 mixture of the adapted sediment communities also dechlorinated PCP without a lag phase. Dechlorination by the mixture was regiospecific, following a para greater than ortho greater than meta order of chlorine removal. Intermediate products of degradation, 2,3,5,6-tetrachlorophenol, 2,3,5-trichlorophenol, 3,5-DCP, 3-CP, and phenol, were identified by a combination of cochromatography (high-pressure liquid chromatography) with standards and gas chromatography-mass spectrometry. PMID:1768102

18. Electrocatalytic activity of Pd-loaded Ti/TiO2 nanotubes cathode for TCE reduction in groundwater.

    PubMed

    Xie, Wenjing; Yuan, Songhu; Mao, Xuhui; Hu, Wei; Liao, Peng; Tong, Man; Alshawabkeh, Akram N

    2013-07-01

    A novel cathode, Pd loaded Ti/TiO2 nanotubes (Pd-Ti/TiO2NTs), is synthesized for the electrocatalytic reduction of trichloroethylene (TCE) in groundwater. Pd nanoparticles are successfully loaded on TiO2 nanotubes which grow on Ti plate via anodization. Using Pd-Ti/TiO2NTs as the cathode in an undivided electrolytic cell, TCE is efficiently and quantitatively transformed to ethane. Under conditions of 100 mA and pH 7, the removal efficiency of TCE (21 mg/L) is up to 91% within 120 min, following pseudo-first-order kinetics with the rate constant of 0.019 min(-1). Reduction rates increase from 0.007 to 0.019 min(-1) with increasing the current from 20 to 100 mA, slightly decrease in the presence of 10 mM chloride or bicarbonate, and decline with increasing the concentrations of sulfite or sulfide. O2 generated at the anode slightly influences TCE reduction. At low currents, TCE is mainly reduced by direct electron transfer on the Pd-Ti/TiO2NT cathode. However, the contribution of Pd-catalytic hydrodechlorination, an indirect reduction mechanism, becomes significant with increasing the current. Compared with other common cathodes, i.e., Ti-based mixed metal oxides, graphite and Pd/Ti, Pd-Ti/TiO2NTs cathode shows superior performance for TCE reduction. Copyright © 2013 Elsevier Ltd. All rights reserved.

19. Electromagnetic induction of nanoscale zerovalent iron particles accelerates the degradation of chlorinated dense non-aqueous phase liquid: Proof of concept.

    PubMed

    Phenrat, Tanapon; Kumloet, Itsaraphong

    2016-12-15

    In this study, a novel electromagnetically enhanced treatment concept is proposed for in situ remediation of a source zone of chlorinated dense non-aqueous phase liquid (DNAPL) that is slowly dissolved, causing contaminated groundwater for centuries. Here, we used polystyrene sulfonate (PSS)-modified nanoscale zerovalent iron (NZVI) particles (ferromagnetic) in combination with a low frequency (LF) (150 kHz) AC electromagnetic field (EMF) to accelerate the degradation of the DNAPLs via enhanced dissolution and reductive dechlorination. Trichloroethylene (TCE) and tetrachloroethylene (PCE) were used in a bench-scaled evaluation. The PSS-modified NZVI successfully targeted the DNAPL/water interface, as evidenced by the Pickering emulsion formation. Dechlorination of TCE- and PCE-DNAPL was measured by quantifying the by-product formation (acetylene, ethene, and ethane). Without magnetic induction heating (MIH) by LF EMF, PSS-modified NZVI transformed TCE- and PCE-DNAPL to ethene and ethane at the rate constants of 12.19 × 10 -3 and 1.00 × 10 -3  μmol/h/m 2 , respectively, following pseudo zero-order reactions. However, four MIH cycles of PSS-NZVI increased the temperature up to 87 °C and increased the rate constants of TCE-DNAPL and PCE-DNAPL up to 14.58 and 58.01 times, respectively, in comparison to the dechlorination rate without MIH. Theoretical analysis suggested that the MIH of the PSS-modified NZVI enhanced the dechlorination of TCE- and PCE-DNAPL via the combination of the enhanced thermal dissolution of DNAPL, the effect of increasing the temperature on the rate constant (the Arrhenius equation), and the accelerated NZVI corrosion. Nevertheless, the effect of the Arrhenius equation was dominant. For the first time, this proof-of-concept study reveals the potential for using polyelectrolyte-modified NZVI coupled with LF EMF as a combined remediation technique for increasing the rate and completeness of in situ chlorinated DNAPL source remediation

Dechlorination of Aromatic Xenobiotic Compounds by Anaerobic Microorganisms

DTIC Science & Technology

1988-07-01

DCB-l likely can also live as a scavenger because it was isolated on rumen fluid and responded with improved growth when rumen fluid or trypticase... rumen fluid markedly enhanced the dechlorinating activity. The activity was increased from ca 13 IM to 75 pM per day and the lag period was reduced from...4 weeks to 3 days in presence of either 0.1 percent yeast extract or 5 percent rumen fluid. The study also suggested that the dechlorinating activity

Removal of gaseous trichloroethylene (TCE) in a composite membrane biofilm reactor.

PubMed

Kumar, Amit; Vercruyssen, Aline; Dewulf, Jo; Lens, Piet; Van Langenhove, Herman

2012-01-01

A membrane biofilm reactor (MBfR) was investigated for the degradation of trichloroethylene (TCE) vapors inoculated by Burkholderia vietnamiensis G4. Toluene (TOL) was used as the primary substrate. The MBfR was loaded sequentially with TOL, TCE (or both) during 110 days. In this study, a maximum steady-state TCE removal efficiency of 23% and a maximum volumetric elimination capacity (EC) of 2.1 g m(-3) h(-1) was achieved. A surface area based maximum elimination capacity (EC(m)) of 4.2 × 10(-3) g m(-2) h(-1) was observed, which is 2-10 times higher than reported in other gas phase biological treatment studies. However, further research is needed to optimize the TCE feeding cycle and to evaluate the inhibiting effects of TCE and its intermediates on TOL biodegradation.

pH Control for Effective Anaerobic Bioremediation of Chlorinated Solvents

NASA Astrophysics Data System (ADS)

Robinson, C.; Barry, D.; Gerhard, J. I.; Kouznetsova, I.

2007-12-01

SABRE (Source Area BioREmediation) is a 4-year collaborative project that aims to evaluate the performance of enhanced anaerobic bioremediation for the treatment of chlorinated solvent DNAPL source areas. The project focuses on a pilot scale demonstration at a trichloroethene (TCE) DNAPL field site, and includes complementary laboratory and modelling studies. Organic acids and hydrogen ions (HCl) typically build up in the treatment zone during anaerobic bioremediation. In aquifer systems with relatively low buffering capacity the generation of these products can cause significant groundwater acidification thereby inhibiting dehalogenating activity. Where the soil buffering capacity is exceeded, addition of buffer may be needed for the effective continuation of TCE degradation. As an aid to the design of remediation schemes, a geochemical model was designed to predict the amount of buffer required to maintain the source zone pH at a suitable level for dechlorinating bacteria (i.e. > 6.5). The model accounts for the amount of TCE to be degraded, site water chemistry, type of organic amendment and soil mineralogy. It assumes complete dechlorination of TCE, and further considers mineral dissolution and precipitation kinetics. The model is applicable to a wide range of sites. For illustration we present results pertinent to the SABRE field site. Model results indicate that, for the extensive dechlorination expected in proximity to the SABRE DNAPL source zone, significant buffer addition may be necessary. Additional simulations are performed to identify buffer requirements over a wider range of field conditions.

Effects of particle composition and environmental parameters on catalytic hydrodechlorination of trichloroethylene by nanoscale bimetallic Ni-Fe.

PubMed

Wei, Jianjun; Qian, Yajing; Liu, Wenjuan; Wang, Lutao; Ge, Yijie; Zhang, Jianghao; Yu, Jiang; Ma, Xingmao

2014-05-01

Catalytic nickel was successfully incorporated into nanoscale iron to enhance its dechlorination efficiency for trichloroethylene (TCE), one of the most commonly detected chlorinated organic compounds in groundwater. Ethane was the predominant product. The greatest dechlorination efficiency was achieved at 22 molar percent of nickel. This nanoscale Ni-Fe is poorly ordered and inhomogeneous; iron dissolution occurred whereas nickel was relatively stable during the 24-hr reaction. The morphological characterization provided significant new insights on the mechanism of catalytic hydrodechlorination by bimetallic nanoparticles. TCE degradation and ethane production rates were greatly affected by environmental parameters such as solution pH, temperature and common groundwater ions. Both rate constants decreased and then increased over the pH range of 6.5 to 8.0, with the minimum value occurring at pH 7.5. TCE degradation rate constant showed an increasing trend over the temperature range of 10 to 25°C. However, ethane production rate constant increased and then decreased over the range, with the maximum value occurring at 20°C. Most salts in the solution appeared to enhance the reaction in the first half hour but overall they displayed an inhibitory effect. Combined ions showed a similar effect as individual salts. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Electrocatalytic Dechlorination Of A PCB Congener At A Palladized Granular Graphite-Packed Electrode: Reaction Equilibrium And Mechanism

EPA Science Inventory

Our previous study on the electrocatalytic dechlorination of 2-chlorobiphenyl at a Pd-loaded granular graphite-packed electrode demonstrated that the process did not follow the first order kinetics. The rate constant varied with the applied potential at the beginning, but later b...

USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

EPA Science Inventory

Granular graphite is a potential electrode material for the electrochemical remediation of refractory chlorinated organic compounds such as trichloroethylene (TCE). However, the use of granular graphite can complicate the experimental results. On one hand, up to 99% of TCE was re...

77 FR 6863 - Proposed Collection; Comment Request for VITA/TCE Program Forms

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-09

.../TCE Program Forms AGENCY: Internal Revenue Service (IRS), Treasury. ACTION: Notice and request for... VITA/TCE Program Forms 14310, 8653, 8654, and 14024. DATES: Written comments should be received on or... . SUPPLEMENTARY INFORMATION: Title: VITA/TCE Program Forms. OMB Number: 1545-2222. Form Number: Forms 14310, 8653...

TRICHLOROETHYLENE (TCE) ISSUE PAPERS

EPA Science Inventory

These issue papers are a part of EPA's effort to develop a trichloroethylene (TCE) human health risk assessment. These issue papers were developed by EPA to provide scientific and technical information to the National Academy of Sciences (NAS) for use in developing their advice ...

PALLADIUM-FACILITATED ELECTROLYTIC DECHLORINATION OF 2-CHLOROBIPHENYL USING A GRANULAR-GRAPHITE ELECTRODE.

EPA Science Inventory

Palladium-assisted electrocatalytic dechlorination of 2-chlorobiphenyl (2-Cl BP) in aqueous solutions was conducted in a membrane-separated electrochemical reactor with granular-graphite packed electrodes. The dechlorination took place at a granular-graphite cathode while Pd was ...

Biodegradation of Trichloroethylene by an Endophyte of Hybrid Poplar

PubMed Central

Kang, Jun Won; Khan, Zareen

2012-01-01

We isolated and characterized a novel endophyte from hybrid poplar. This unique endophyte, identified as Enterobacter sp. strain PDN3, showed high tolerance to trichloroethylene (TCE). Without the addition of inducers, such as toluene or phenol, PDN3 rapidly reduced TCE levels in medium from 72.4 μM to 30.1 μM in 24 h with a concurrent release of 127 μM chloride ion, and nearly 80% of TCE (55.3 μM) was dechlorinated by PDN3 in 5 days with 166 μM chloride ion production, suggesting TCE degradation. PMID:22367087

Photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin by Pd modified g-C3N4 photocatalysts under UV-vis irradiation: Efficacy, kinetics and mechanism.

PubMed

Ding, Jiafeng; Long, Gaoyuan; Luo, Yang; Sun, Runze; Chen, Mengxia; Li, Yajun; Zhou, Yanfang; Xu, Xinhua; Zhao, Weirong

2018-05-09

Polychlorinated dibenzo-p-dioxins (PCDDs), as a group of notorious anthropogenic environmental toxicants, are arguably ubiquitous in nature. In this study, we investigated the photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin (2-CDD) over Pd/g-C 3 N 4 catalysts under UV-vis irradiation. The g-C 3 N 4 and a series of Pd/g-C 3 N 4 catalysts were prepared by thermal polymerization and mechanical mixing-illumination method and characterized by XRD, TEM, BET, SEM and UV-vis DRS analyses. Among all the samples, the Pd/g-C 3 N 4 (5 wt%) yielded the optimal dechlorination activity with a total 2-CDD conversion of 54% within 4 h, and 76% of those converted 2-CDD were evolved to dibenzo-p-dioxin (DD). The kinetics of dechlorination could be described as pseudo-first-order decay model (R 2  > 0.84). Corresponding rate constants (k) increased from 0.052 to 0.17 h -1 with Pd contents up to 5 wt% and decreased to 0.13 h -1 with a 10 wt% of Pd. The enhanced activities originated from the surface plasmonic resonance (SPR) effect of Pd nanoparticles and the formation of Schottky barrier between Pd and g-C 3 N 4 , which extend the spectrum responsive range and suppress the charge recombination of g-C 3 N 4 . This is the first report on the photocatalytic reductive removal of PCDDs and may provide a new approach for PCDDs pollution control. Copyright © 2018 Elsevier B.V. All rights reserved.

BIODEGRADATION OF PCE AND TCE IN LANDFILL, LEACHATE PREDICTED FROM CONCENTRATIONS OF MOLECULAR HYDROGEN: A CASE STUDY

EPA Science Inventory

The Refuse Hideaway Landfill (23-acre) was designed as a "natural attenuation" landfill and no provision was made to collect and treat contaminated water. Natural biological degradation through sequential reductive dechlorination had been an important mechanism for natural atten...

Microbial based chlorinated ethene destruction

DOEpatents

Bagwell, Christopher E [Aiken, SC; Freedman, David L [Clemson, SC; Brigmon, Robin L [North Augusta, SC; Bratt, William B [Atlanta, GA; Wood, Elizabeth A [Marietta, GA

2009-11-10

A mixed culture of Dehalococcoides species is provided that has an ability to catalyze the complete dechlorination of polychlorinated ethenes such as PCE, TCE, cDCE, 1,1-DCE and vinyl chloride as well as halogenated ethanes such as 1,2-DCA and EDB. The mixed culture demonstrates the ability to achieve dechlorination even in the presence of high source concentrations of chlorinated ethenes.

Dechlorination of polychlorinated biphenyls in industrial transformer oil by radiolytic and photolytic methods.

PubMed

Jones, Cynthia G; Silverman, Joseph; Al-Sheikhly, Mohamad; Neta, Pedatsur; Poster, Dianne L

2003-12-15

Used electrical transformer oils containing low or high concentrations of polychlorinated biphenyls (PCBs) were treated using electron, gamma, and ultraviolet radiation, and the conditions for complete dechlorination were developed. Dechlorination was determined by analysis of the inorganic chloride formed and the concentrations of remaining PCBs. Transformer oil containing approximately 95 microg g(-1) PCB (approximately 3.5 mmol L(-1) Cl) is completely dechlorinated by irradiation with 600 kGy after the addition of 10% triethylamine (TEA). Transformer oil containing >800,000 microg g(-1) PCB (17.7 mol L(-1) Cl) requires an additional solvent to prevent solidification. When this oil is diluted with 2-propanol (2-PrOH) and TEA (v/v/v, 1/79/20), complete dechlorination is achieved with a dose of 2500 kGy. Ultraviolet photolysis of the same oil/2-PrOH/TEA solutions led to 90% dechlorination after exposure for 120 h in our experimental setup. Such yields were obtained by radiolysis with a dose of 2000 kGy (300 h in our Gammacell). Replacing TEA with KOH in 2-PrOH solutions greatly increases the yield of dechlorination in both the radiolytic and the photolytic experiments, demonstrating that a chain reaction plays a role in both of these treatment methods and suggesting that both methods deserve further consideration for large-scale application.

Dechlorination of pentachlorophenol, 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid in anaerobic freshwater sediments

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

Bryant, F.O.; Rogers, J.E.

1990-02-01

Pentachlorophenol, 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid were transformed by microbial reductive dechlorination in freshwater, anaerobic sediments from such diverse locations as Georgia, Florida, New York and the Soviet Union. The reductive dechlorination process involves removal of a chlorine and replacement with a hydrogen. Sediments previously adapted to dechlorinate dichlorophenols were found to mediate dechlorination at much faster rates than unadapted sediments. Pentachlorophenol dechlorination in dichlorophenol-adapted sediments generated tetra-, tri-, di-, and monochlorophenol and phenol. Concentrations of pentachlorophenol, 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid up to 100 ppm were dechlorinated by adapted sediments. Reductive dechlorination of PCP, 2,4-D, and 2,4,5-T was regionmore » specific for chlorine removal as determined by the dichlorophenol isomer used to adapt the sediment. Sediment adapted to 2,4-dichlorophenol preferentially removed chlorines from the ortho position; whereas sediment adapted to 3,4-dichlorophenol preferentially removed chlorines from the para position.« less

Degradation of phenol and TCE using suspended and chitosan-bead immobilized Pseudomonas putida.

PubMed

Chen, Yan-Min; Lin, Tsair-Fuh; Huang, Chih; Lin, Jui-Che; Hsieh, Feng-Ming

2007-09-30

The degradability of phenol and trichloroethene (TCE) by Pseudomonas putida BCRC 14349 in both suspended culture and immobilized culture systems are investigated. Chitosan beads at a size of about 1-2mm were employed to encapsulate the P. putida cells, becoming an immobilized culture system. The phenol concentration was controlled at 100 mg/L, and that of TCE was studied from 0.2 to 20 mg/L. The pH, between 6.7 and 10, did not affect the degradation of either phenol or TCE in the suspended culture system. However, it was found to be an important factor in the immobilized culture system in which the only significant degradation was observed at pH >8. This may be linked to the surface properties of the chitosan beads and its influence on the activity of the bacteria. The transfer yield of TCE on a phenol basis was almost the same for the suspended and immobilized cultures (0.032 mg TCE/mg phenol), except that these yields occurred at different TCE concentrations. The transfer yield at a higher TCE concentration for the immobilized system suggested that the cells immobilized in carriers can be protected from harsh environmental conditions. For kinetic rate interpretation, the Monod equation was employed to describe the degradation rates of phenol, while the Haldane's equation was used for TCE degradation. Based on the kinetic parameters obtained from the two equations, the rate for the immobilized culture systems was only about 1/6 to that of the suspended culture system for phenol degradation, and was about 1/2 for TCE degradation. The slower kinetics observed for the immobilized culture systems was probably due to the slow diffusion of substrate molecules into the beads. However, compared with the suspended cultures, the immobilized cultures may tolerate a higher TCE concentration as much less inhibition was observed and the transfer yield occurred at a higher TCE concentration.

Factors influencing the development of a biostimulant for the in-situ anaerobic dechlorination of polychlorinated biphenyls in Fox River, Wisconsin sediments

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

Hollifield, M.B.; Park, J.K.; Boyle, W.C.

1995-12-31

Polychlorinated biphenyl (PCB) contaminated sediments were collected from the Fox River, Wisconsin, and analyzed for the possible occurrence of reductive dechlorination. Evidence of in-situ dechlorination was observed. However, the extent of this in-situ dechlorination was less than that typically reported in the literature, suggesting that stimulation of further dechlorination was possible. The use of nutrients and surfactants was explored for stimulating additional dechlorination. The nutrient amendment reported here was found to be inhibitory. Surfactants had varying effect, but non significantly improved dechlorination over control treatments. The most significant factors were observed to be the initial extent of dechlorination and PCBmore » concentration. Additional dechlorination was most likely to be observed in sediments with higher PCB concentration and less initial dechlorination. All sediments converged on a common dechlorination level regardless of the initial state of the sediments.« less

Establishment of a Polychlorinated Biphenyl-Dechlorinating Microbial Consortium, Specific for Doubly Flanked Chlorines, in a Defined, Sediment-Free Medium

PubMed Central

Wu, Qingzhong; Sowers, Kevin R.; May, Harold D.

2000-01-01

Estuarine sediment from Charleston Harbor, South Carolina, was used as inoculum for the development of an anaerobic enrichment culture that specifically dechlorinates doubly flanked chlorines (i.e., chlorines bound to carbon that are flanked on both sides by other chlorine-carbon bonds) of polychlorinated biphenyls (PCBs). Dechlorination was restricted to the para chlorine in cultures enriched with 10 mM fumarate, 50 ppm (173 μM) 2,3,4,5-tetrachlorobiphenyl, and no sediment. Initially the rate of dechlorination decreased upon the removal of sediment from the medium. However, the dechlorinating activity was sustainable, and following sequential transfer in a defined, sediment-free estuarine medium, the activity increased to levels near that observed with sediment. The culture was nonmethanogenic, and molybdate, ampicillin, chloramphenicol, neomycin, and streptomycin inhibited dechlorination activity; bromoethanesulfonate and vancomycin did not. Addition of 17 PCB congeners indicated that the culture specifically removes double flanked chlorines, preferably in the para position, and does not attack ortho chlorines. This is the first microbial consortium shown to para or meta dechlorinate a PCB congener in a defined sediment-free medium. It is the second PCB-dechlorinating enrichment culture to be sustained in the absence of sediment, but its dechlorinating capabilities are entirely different from those of the other sediment-free PCB-dechlorinating culture, an ortho-dechlorinating consortium, and do not match any previously published Aroclor-dechlorinating patterns. PMID:10618202

Effects of Reduced Sulfur Compounds on Pd-catalytic Hydrodechlorination of TCE in Groundwater by Cathodic H2 under Electrochemically-induced Oxidizing Conditions

PubMed Central

Yuan, Songhu; Chen, Mingjie; Mao, Xuhui; Alshawabkeh, Akram N.

2014-01-01

Reduced sulfur compounds (RSCs) poison Pd catalysts for catalytic hydrodechlorination of contaminants in anoxic groundwater. This study investigates the effects of RSCs on Pd-catalytic hydrodechlorination of trichloroethylene (TCE) in oxic groundwater. Water electrolysis in an undivided electrolytic cell is used to produce H2 for TCE hydrodechlorination under oxidizing conditions. TCE is efficiently hydrodechlorinated to ethane, with significant accumulation of H2O2 under acidic conditions. Presence of sulfide at concentrations less than 93.8 μM moderately inhibits TCE hydrodechlorination and H2O2 production. Presence of sulfite at low concentrations (≤ 1 mM) significantly enhances TCE decay, while at high concentration (3 mM) inhibits initially and enhances afterwards when sulfite concentration declines to less than 1 mM. Using radical scavenging experiments and electron spin resonance assay, SO3•− which is generated from sulfite under oxidizing conditions is validated as the new reactive species contributing to the enhancement. This study reveals a distinct mechanism of effect of sulfite on TCE hydrodechlorination by Pd and H2 in oxic groundwater and presents an alternative approach to increasing resistance of Pd to RSCs poisoning. PMID:23962132

ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES: IDENTIFICATION AND QUANTIFICATION OF DECHLORINATION PRODUCTS

EPA Science Inventory

Electrochemical degradation (ECD) utilizes high redox potential at the anode and low redox potential at the cathode to oxidize and/or reduce organic and inorganic contaminants. ECD of Trichloroethylene (TCE), although theoretically possible, has not been experimentally proven. Th...

Degradation of TCE using sequential anaerobic biofilm and aerobic immobilized bed reactor

NASA Technical Reports Server (NTRS)

Chapatwala, Kirit D.; Babu, G. R. V.; Baresi, Larry; Trunzo, Richard M.

1995-01-01

Bacteria capable of degrading trichloroethylene (TCE) were isolated from contaminated wastewaters and soil sites. The aerobic cultures were identified as Pseudomonas aeruginosa (four species) and Pseudomonas fluorescens. The optimal conditions for the growth of aerobic cultures were determined. The minimal inhibitory concentration values of TCE for Pseudomonas sps. were also determined. The aerobic cells were immobilized in calcium alginate in the form of beads. Degradation of TCE by the anaerobic and dichloroethylene (DCE) by aerobic cultures was studied using dual reactors - anaerobic biofilm and aerobic immobilized bed reactor. The minimal mineral salt (MMS) medium saturated with TCE was pumped at the rate of 1 ml per hour into the anaerobic reactor. The MMS medium saturated with DCE and supplemented with xylenes and toluene (3 ppm each) was pumped at the rate of 1 ml per hour into the fluidized air-uplift-type reactor containing the immobilized aerobic cells. The concentrations of TCE and DCE and the metabolites formed during their degradation by the anaerobic and aerobic cultures were monitored by GC. The preliminary study suggests that the anaerobic and aerobic cultures of our isolates can degrade TCE and DCE.

Monitoring Natural Biodegradation of TCE in Fractured Sedimentary Rocks Using delta 13C of TCE and its Degradation Products: Estimating Isotopic Fractionation Factor under Field Conditions

NASA Astrophysics Data System (ADS)

Revesz, K.; Shapiro, A. M.; Tiedeman, C.; Goode, D. J.; Lacombe, P. J.; Imbrigiotta, T. E.

2008-12-01

The isotopic ratio of 13C/12C, expressed in delta13CVPDB per mill for trichloroethene (TCE), can differentiate between microbial degradation and other processes (dilution, dispersion, and sorption) that can also affect the concentration of TCE and its degradation products. The delta13C of TCE isotopically fractionates during microbial degradation; however, it remains practically unchanged during other processes. The isotope fractionation factor (alpha) estimated under laboratory conditions, however, may not be representative of microbial degradation in natural ground waters. Estimating alpha under field conditions provides evidence of the presence or absence of in situ microbial degradation and provides valuable information on the in situ processes that affect the fate and transport of chlorinated hydrocarbons. Our modified analytical method of analyzing for the isotopic ratio proved to be comparable to previously published methods. Isotope values were stable within analytical uncertainty in sample sizes ranging from 22 to 2200 nanomoles. Prepared standard mixtures of TCE and DCEs (trans- and cis- dichloroethene) were analyzed after every five field samples, and were stable during the time period that field samples were processed (a year). Water samples were collected from multiple boreholes completed in the fractured mudstone underlying the former Naval Air Warfare Center, West Trenton, NJ, and analyzed for delta13C of the chlorinated hydrocarbons. The results showed an ongoing natural microbial degradation following the typical dehalogenation pathway: TCE to DCE (trans- and cis-dichloroethene) to VC (vinyl chloride). The carbon isotope enrichment due to fractionation was smaller between TCE to DCE degradation than the enrichment between DCE to VC degradation, which is consistent with previous investigations. Results also showed a correlation between delta13C of TCE and the transmissivity of the boreholes where water samples were collected. We assumed that

Development of KMnO(4)-releasing composites for in situ chemical oxidation of TCE-contaminated groundwater.

PubMed

Liang, S H; Chen, K F; Wu, C S; Lin, Y H; Kao, C M

2014-05-01

The objective of this study was to develop a controlled-oxidant-release technology combining in situ chemical oxidation (ISCO) and permeable reactive barrier (PRB) concepts to remediate trichloroethene (TCE)-contaminated groundwater. In this study, a potassium permanganate (KMnO4)-releasing composite (PRC) was designed for KMnO4 release. The components of this PRC included polycaprolactone (PCL), KMnO4, and starch with a weight ratio of 1.14:2:0.96. Approximately 64% (w/w) of the KMnO4 was released from the PRC after 76 days of operation in a batch system. The results indicate that the released KMnO4 could oxidize TCE effectively. The results from a column study show that the KMnO4 released from 200 g of PRC could effectively remediate 101 pore volumes (PV) of TCE-contaminated groundwater (initial TCE concentration = 0.5 mg/L) and achieve up to 95% TCE removal. The effectiveness of the PRC system was verified by the following characteristics of the effluents collected after the PRC columns (barrier): (1) decreased TCE concentrations, (2) increased ORP and pH values, and (3) increased MnO2 and KMnO4 concentrations. The results of environmental scanning electron microscope (ESEM) analysis show that the PCL and starch completely filled up the pore spaces of the PRC, creating a composite with low porosity. Secondary micro-scale capillary permeability causes the KMnO4 release, mainly through a reaction-diffusion mechanism. The PRC developed could be used as an ISCO-based passive barrier system for plume control, and it has the potential to become a cost-effective alternative for the remediation of chlorinated solvent-contaminated groundwater. Copyright © 2014 Elsevier Ltd. All rights reserved.

Novel Firmicutes Group Implicated in the Dechlorination of Two Chlorinated Xanthones, Analogues of Natural Organochlorines

PubMed Central

Krzmarzick, Mark J.; Miller, Hanna R.; Yan, Tao

2014-01-01

Although the abundance and diversity of natural organochlorines are well established, much is still unknown about the degradation of these compounds. Triplicate microcosms were used to determine whether, and which, bacterial communities could dechlorinate two chlorinated xanthones (2,7-dichloroxanthone and 5,7-dichloro-1,3-dihydroxylxanthone), analogues of a diverse class of natural organochlorines. According to quantitative-PCR (qPCR) results, several known dechlorinating genera were either not present or not enriched during dechlorination of the xanthones. Denaturing gradient gel electrophoresis, however, indicated that several Firmicutes were enriched in the dechlorinating cultures compared to triplicate controls amended with nonchlorinated xanthones. One such group, herein referred to as the Gopher group, was further studied with a novel qPCR method that confirmed enrichment of Gopher group 16S rRNA genes in the dechlorinating cultures. The enrichment of the Gopher group was again tested with two new sets of triplicate microcosms. Enrichment was observed during chlorinated xanthone dechlorination in one set of these triplicate microcosms. In the other set, two microcosms showed clear enrichment while a third did not. The Gopher group is a previously unidentified group of Firmicutes, distinct from but related to the Dehalobacter and Desulfitobacterium genera; this group also contains clones from at least four unique cultures capable of dechlorinating anthropogenic organochlorines that have been previously described in the literature. This study suggests that natural chlorinated xanthones may be effective biostimulants to enhance the remediation of pollutants and highlights the idea that novel genera of dechlorinators likely exist and may be active in bioremediation and the natural cycling of chlorine. PMID:24296507

[Effect of composting organic fertilizer supplies on hexachlorobenzene dechlorination in paddy soils].

PubMed

Liu, Cui-Ying; Jiang, Xin

2013-04-01

A rice pot experiment was conducted in two soils, Hydragric Acrisols (Ac) and Gleyi-Stagnic Anthrosols (An). Three treatments including control and additions of 1% or 2% composting organic fertilizer were designed for each soil. The objective of this research was to evaluate the reductive dechlorination of hexachlorobenzene (HCB) as affected by organic fertilizer supplies in planted paddy soils, and to analyze the relationship between methane production and HCB dechlorination. The results showed that the HCB residues were decreased by 28.6%-30.1% of the initial amounts in Ac, and 47.3% -61.0% in An after 18 weeks of experiment. The amount of HCB and its metabolite uptake by rice plants was only a few thousandths of the initial HCB amount in soils. The main product of HCB dechlorination was pentachlorobenzene (PeCB). The rates of HCB dechlorination in An were higher than those in Ac, which was mainly attributed to the higher pH and dissolved organic carbon (DOC) content of An. The applications of both 1% and 2% composting organic fertilizer showed significant inhibition on PeCB production after the 6th and 10th week in Ac and An, respectively. In both tested soils, no significant difference of PeCB production rates was observed between the applications of 1% and 2% composting organic fertilizer. The role of methanogenic bacteria in HCB dechlorination was condition-dependent.

Comparison of Alternative Hydrogen Donors for Anaerobic Reductive Dechlorination of Tetrachloroethene

DTIC Science & Technology

1998-01-01

feature two - stage anaerobic reductive dechlorination of highly chlorinated compounds coupled with aerobic (sometimes co- metabolic) treatment of the...activity at some naturally attenuated sites. Fathepure and Vogel [76] used a two - stage anaerobic-aerobic reactor system to treat hexachlorobenzene, PCE...Complete removal of the chloroethenes by the two - stage system was observed using pyruvate, formate, or lactose as electron donor for the dechlorinating

Degradation of trichloroethylene in aqueous solution by rGO supported nZVI catalyst under several oxic environments.

PubMed

Gu, Mengbin; Farooq, Usman; Lu, Shuguang; Zhang, Xiang; Qiu, Zhaofu; Sui, Qian

2018-05-05

The reduced graphene oxide (rGO) supported nano zero-valent iron (nZVI) (nZVI-rGO) was synthesized successfully and applied in the several oxic environments to remove trichloroethylene (TCE). The nZVI-rGO had a better catalytic performance than bare nZVI for the TCE removal. Both aggregation of nZVI and agglomeration of rGO were in part prevented by loading the nZVI nanoparticles on the rGO sheet. Among all the oxic environments, the better removal of TCE was followed as the order of PMS > SPS > H 2 O 2 . Chemical scavenger tests were carried out to identify the reactive oxygen species (ROSs) generated in the removal of TCE, showing that in PMS and SPS systems, SO 4 - and HO were main radicals responsible for TCE removal, while HO and O 2 - were main radicals in H 2 O 2 system. The possible mechanisms were proposed with nZVI-rGO under several oxic environments. The recyclability of nZVI-rGO, dechlorination and mineralization of TCE were investigated. These fundamental data confirmed the effectiveness of nZVI-rGO to remove TCE and could help selecting the suitable oxidants to use with nZVI-rGO in the actual field groundwater remediation. Copyright © 2018 Elsevier B.V. All rights reserved.

Dechlorination of chlorinated phenols by subnanoscale Pd 0 /Fe 0 intercalated in smectite: pathway, reactivity, and selectivity.

PubMed

Jia, Hanzhong; Wang, Chuanyi

2015-12-30

Smectite clay was employed as templated matrix to prepare subnanoscale Pd(0)/Fe(0) particles, and their components as well as intercalated architectures were well characterized by X-ray energy dispersive spectroscopy (X-EDS) and X-ray diffraction (XRD). Furthermore, as-prepared Pd(0)/Fe(0) subnanoscale nanoparticles were evaluated for their dechlorination effect using chlorinated phenols as model molecules. As a result, pentachlorophenol (PCP) is selectively transformed to phenol in a stepwise dechlorination pathway within 6h, and the dechlorination rate constants show linearly relationship with contents of Pd as its loadings <0.065%. Comparing with PCP, other chlorinated phenols display similar degradation pattern but within much shorter time frame. The dechlorination rate of chlorinated phenols increases with decreasing in number of -Cl attached to aromatic ring, which can be predicted by the total charge of the aromatic ring, exhibiting an inversely linear relationship with the dechlorination rates. While the selectivity of dechlorination depends on the charges associated with the individual aromatic carbon. Chloro-functional groups at the ortho-position are easier to be dechlorinated than that at meta- and para- positions yielding primarily 3,4,5-TCP as intermediate from PCP, further to phenol. The effective dechlorination warrants their potential utilizations in development of in-situ remediation technologies for organic pollutants in contaminated water. Copyright © 2015 Elsevier B.V. All rights reserved.

Assessing TCE source bioremediation by geostatistical analysis of a flux fence.

PubMed

Cai, Zuansi; Wilson, Ryan D; Lerner, David N

2012-01-01

Mass discharge across transect planes is increasingly used as a metric for performance assessment of in situ groundwater remediation systems. Mass discharge estimates using concentrations measured in multilevel transects are often made by assuming a uniform flow field, and uncertainty contributions from spatial concentration and flow field variability are often overlooked. We extend our recently developed geostatistical approach to estimate mass discharge using transect data of concentration and hydraulic conductivity, so accounting for the spatial variability of both datasets. The magnitude and uncertainty of mass discharge were quantified by conditional simulation. An important benefit of the approach is that uncertainty is quantified as an integral part of the mass discharge estimate. We use this approach for performance assessment of a bioremediation experiment of a trichloroethene (TCE) source zone. Analyses of dissolved parent and daughter compounds demonstrated that the engineered bioremediation has elevated the degradation rate of TCE, resulting in a two-thirds reduction in the TCE mass discharge from the source zone. The biologically enhanced dissolution of TCE was not significant (~5%), and was less than expected. However, the discharges of the daughter products cis-1,2, dichloroethene (cDCE) and vinyl chloride (VC) increased, probably because of the rapid transformation of TCE from the source zone to the measurement transect. This suggests that enhancing the biodegradation of cDCE and VC will be crucial to successful engineered bioremediation of TCE source zones. © 2012, The Author(s). Ground Water © 2012, National Ground Water Association.

Developmental neurotoxic effects of a low dose of TCE on a 3-D neurosphere system.

PubMed

Abdraboh, M E; Abdeen, S H; Salama, M; El-Husseiny, M; El-Sherbini, Y M; Eldeen, N M

2018-02-01

Trichloroethylene (TCE) is one of the industrial toxic byproducts that now persist in the air, soil, and water. Several studies have already illustrated the toxic effect of high doses of TCE on the biological functions of several organs. This study aims to highlight the toxic impact of a low dose of TCE (1 μmol/L) on the development of rat neural stem cells (NSCs). The subventricular zones (SVZ) of rat pup's brains were collected and minced, and the harvested cells were cultured in the presence of neural growth factors B27/N2 to develop neurospheres. The cells were then exposed to a dose of 1 μmol/L TCE for 1 or 2 weeks. The outcomes indicated a remarkable inhibitory effect of TCE on the differentiation capacity of NSCs, which was confirmed by down-regulation of the astrocyte marker GFAP The inhibitory effect of TCE on the proliferation of NSCs was identified by the reductions in neurosphere diameter, Ki67 expression, and cell cycle arrest at the G1/S phase. Immunolabelling with annexin V indicated the proapoptotic effect of TCE exposure. PCR results revealed a TCE-mediated suppression of the expression of the antioxidant enzyme SOD1. This paper illustrates, for the first time, a detailed examination of the toxic effects of an environmentally low dose of TCE on NCSs at the transcriptional, translational, and functional levels.

Photocatalysis of gaseous trichloroethylene (TCE) over TiO2: the effect of oxygen and relative humidity on the generation of dichloroacetyl chloride (DCAC) and phosgene.

PubMed

Ou, Hsin-Hung; Lo, Shang-Lien

2007-07-19

Batch photocatalytic degradation of 80+/-2.5 ppm V trichloroethylene (TCE) was conducted to investigate the effect of the oxygen and relative humidity (RH) on the formation of the dichloroacetyl chloride (DCAC) and phosgene. Based on the simultaneous ordinary differential equations (ODEs), the reaction rate constants of TCE ((2.31+/-0.28) approximately (9.41+/-0.63)x10(-2) min(-1)) are generally larger than that of DCAC ((0.94+/-1.25) approximately (9.35+/-1.71)x10(-3) min(-1)) by approximate one order. The phenomenon indicates the degradation potential of TCE is superior to that of DCAC. DCAC appreciably delivers the same degradation behavior with TCE that means there exists an optimum RH and oxygen concentration for photocatalysis of TCE and DCAC. At the time the peak yield of DCAC appears, the conversion ratio based on the carbon atom from TCE to DCAC is within the range of 30-83% suggesting that the DCAC generation is significantly attributed to TCE degradation. Regarding the phosgene formation, the increasing oxygen amount leads to the inhibitory effect on the phosgene yield which fall within the range of 5-15%. The formation mechanism of phosgene was also inferred that the Cl atoms attacking the C-C bond of DCAC results to the generation of phosgene rather than directly from the TCE destruction.

Reductive microbial dechlorination of indigenous polychlorinated biphenyls in soil using a sediment-free inoculum

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

Klasson, K.T.; Barton, J.W.; Evans, B.S.

1996-05-01

In laboratory experiments, unagitated soil slurry bioreactors inoculated with microorganisms extracted from polychlorinated biphenyl-contaminated (PCBs) sediments from the Hudson River were used to anaerobically dechlorinate PCBs. The onset of dechlorination activity was accelerated by the addition of certain organic acids (pyruvate and maleate) and single congeners (2,3,6-trichlorobiphenyl). Dechlorination was observed under several working conditions after 19 weeks of incubation with PCB-contaminated soil and nutrient solution. Best results showed a drop in average chlorine content from 4.3 to 3.6 chlorines per biphenyl due to a loss of m-chlorines. Soil used for these experiments was obtained from a PCB-contaminated (weathered Aroclor 1248)more » site at an electric power substation. Dechlorination was observed with no sediment particles or other matrix being added. 17 refs., 6 figs., 1 tab.« less

Removal of trichloroethylene (TCE) contaminated soil using a two-stage anaerobic-aerobic composting technique.

PubMed

Ponza, Supat; Parkpian, Preeda; Polprasert, Chongrak; Shrestha, Rajendra P; Jugsujinda, Aroon

2010-01-01

The effect of organic carbon addition on remediation of trichloroethylene (TCE) contaminated clay soil was investigated using a two stage anaerobic-aerobic composting system. TCE removal rate and processes involved were determined. Uncontaminated clay soil was treated with composting materials (dried cow manure, rice husk and cane molasses) to represent carbon based treatments (5%, 10% and 20% OC). All treatments were spiked with TCE at 1,000 mg TCE/kg DW and incubated under anaerobic and mesophillic condition (35 degrees C) for 8 weeks followed by continuous aerobic condition for another 6 weeks. TCE dissipation, its metabolites and biogas composition were measured throughout the experimental period. Results show that TCE degradation depended upon the amount of organic carbon (OC) contained within the composting treatments/matrices. The highest TCE removal percentage (97%) and rate (75.06 micro Mole/kg DW/day) were obtained from a treatment of 10% OC composting matrices as compared to 87% and 27.75 micro Mole/kg DW/day for 20% OC, and 83% and 38.08 micro Mole/kg DW/day for soil control treatment. TCE removal rate was first order reaction kinetics. Highest degradation rate constant (k(1) = 0.035 day(- 1)) was also obtained from the 10% OC treatment, followed by 20% OC (k(1) = 0.026 day(- 1)) and 5% OC or soil control treatment (k(1) = 0.023 day(- 1)). The half-life was 20, 27 and 30 days, respectively. The overall results suggest that sequential two stages anaerobic-aerobic composting technique has potential for remediation of TCE in heavy texture soil, providing that easily biodegradable source of organic carbon is present.

Remediation of TCE-contaminated groundwater using acid/BOF slag enhanced chemical oxidation.

PubMed

Tsai, T T; Kao, C M; Wang, J Y

2011-04-01

The objective of this study was to evaluate the potential of applying acid/H(2)O(2)/basic oxygen furnace slag (BOF slag) and acid/S(2)O(8)(2-)/BOF slag systems to enhance the chemical oxidation of trichloroethylene (TCE)-contaminated groundwater. Results from the bench-scale study indicate that TCE oxidation via the Fenton-like oxidation process can be enhanced with the addition of BOF slag at low pH (pH=2-5.2) and neutral (pH=7.1) conditions. Because the BOF slag has iron abundant properties (14% of FeO and 6% of Fe(2)O(3)), it can be sustainably reused for the supplement of iron minerals during the Fenton-like or persulfate oxidation processes. Results indicate that higher TCE removal efficiency (84%) was obtained with the addition of inorganic acid for the activation of Fenton-like reaction compared with the experiments with organic acids addition (with efficiency of 10-15% lower) (BOF slag=10gL(-1); initial pH=5.2). This could be due to the fact that organic acids would compete with TCE for available oxidants. Results also indicate that the pH value had a linear correlation with the observed first-order decay constant of TCE, and thus, lower pH caused a higher TCE oxidation rate. Copyright © 2011 Elsevier Ltd. All rights reserved.

In situ iron activated persulfate oxidative fluid sparging treatment of TCE contamination--a proof of concept study.

PubMed

Liang, Chenju; Lee, I-Ling

2008-09-10

In situ chemical oxidation (ISCO) is considered a reliable technology to treat groundwater contaminated with high concentrations of organic contaminants. An ISCO oxidant, persulfate anion (S(2)O(8)(2-)) can be activated by ferrous ion (Fe(2+)) to generate sulfate radicals (E(o)=2.6 V), which are capable of destroying trichloroethylene (TCE). The property of polarity inhibits S(2)O(8)(2-) or sulfate radical (SO(4)(-)) from effectively oxidizing separate phase TCE, a dense non-aqueous phase liquid (DNAPL). Thus the oxidation primarily takes place in the aqueous phase where TCE is dissolved. A bench column study was conducted to demonstrate a conceptual remediation method by flushing either S(2)O(8)(2-) or Fe(2+) through a soil column, where the TCE DNAPL was present, and passing the dissolved mixture through either a Fe(2+) or S(2)O(8)(2-) fluid sparging curtain. Also, the effect of a solubility enhancing chemical, hydroxypropyl-beta-cyclodextrin (HPCD), was tested to evaluate its ability to increase the aqueous TCE concentration. Both flushing arrangements may result in similar TCE degradation efficiencies of 35% to 42% estimated by the ratio of TCE degraded/(TCE degraded+TCE remained in effluent) and degradation byproduct chloride generation rates of 4.9 to 7.6 mg Cl(-) per soil column pore volume. The addition of HPCD did greatly increase the aqueous TCE concentration. However, the TCE degradation efficiency decreased because the TCE degradation was a lower percentage of the relatively greater amount of dissolved TCE by HPCD. This conceptual treatment may serve as a reference for potential on-site application.

Natural attenuation of chlorinated volatile organic compounds in a freshwater tidal wetland: Field evidence of anaerobic biodegradation

USGS Publications Warehouse

Lorah, Michelle M.; Olsen, Lisa D.

1999-01-01

Field evidence collected along two groundwater flow paths shows that anaerobic biodegradation naturally attenuates a plume of chlorinated volatile organic compounds as it discharges from an aerobic sand aquifer through wetland sediments. A decrease in concentrations of two parent contaminants, trichloroethylene (TCE) and 1,1,2,2‐tetrachloroethane (PCA), and a concomitant increase in concentrations of anaerobic daughter products occurs along upward flow paths through the wetland sediments. The daughter products 1,2‐dichloroethylene, vinyl chloride, 1,1,2‐trichloroethane, and 1,2‐dichloroethane are produced from hydrogenolysis of TCE and from PCA degradation through hydrogenolysis and dichloroelimination (reductive dechlorination) pathways. Total concentrations of TCE, PCA, and their degradation products, however, decrease to below detection levels within 0.15–0.30 m of land surface. The enhanced reductive dechlorination of TCE and PCA in the wetland sediments is associated with the naturally higher concentrations of dissolved organic carbon and the lower redox state of the groundwater compared to the aquifer. This field study indicates that wetlands and similar organic‐rich environments at groundwater/surface‐water interfaces may be important in intercepting groundwater contaminated with chlorinated organics and in naturally reducing concentrations and toxicity before sensitive surface‐water receptors are reached.

Enhanced Degradation of TCE on a Superfund Site Using Endophyte-Assisted Poplar Tree Phytoremediation.

PubMed

Doty, Sharon L; Freeman, John L; Cohu, Christopher M; Burken, Joel G; Firrincieli, Andrea; Simon, Andrew; Khan, Zareen; Isebrands, J G; Lukas, Joseph; Blaylock, Michael J

2017-09-05

Trichloroethylene (TCE) is a widespread environmental pollutant common in groundwater plumes associated with industrial manufacturing areas. We had previously isolated and characterized a natural bacterial endophyte, Enterobacter sp. strain PDN3, of poplar trees, that rapidly metabolizes TCE, releasing chloride ion. We now report findings from a successful three-year field trial of endophyte-assisted phytoremediation on the Middlefield-Ellis-Whisman Superfund Study Area TCE plume in the Silicon Valley of California. The inoculated poplar trees exhibited increased growth and reduced TCE phytotoxic effects with a 32% increase in trunk diameter compared to mock-inoculated control poplar trees. The inoculated trees excreted 50% more chloride ion into the rhizosphere, indicative of increased TCE metabolism in planta. Data from tree core analysis of the tree tissues provided further supporting evidence of the enhanced rate of degradation of the chlorinated solvents in the inoculated trees. Test well groundwater analyses demonstrated a marked decrease in concentration of TCE and its derivatives from the tree-associated groundwater plume. The concentration of TCE decreased from 300 μg/L upstream of the planted area to less than 5 μg/L downstream of the planted area. TCE derivatives were similarly removed with cis-1,2-dichloroethene decreasing from 160 μg/L to less than 5 μg/L and trans-1,2-dichloroethene decreasing from 3.1 μg/L to less than 0.5 μg/L downstream of the planted trees. 1,1-dichloroethene and vinyl chloride both decreased from 6.8 and 0.77 μg/L, respectively, to below the reporting limit of 0.5 μg/L providing strong evidence of the ability of the endophytic inoculated trees to effectively remove TCE from affected groundwater. The combination of native pollutant-degrading endophytic bacteria and fast-growing poplar tree systems offers a readily deployable, cost-effective approach for the degradation of TCE, and may help mitigate potential transfer up

Reductive dechlorination in recalcitrant sources of chloroethenes in the transition zone between aquifers and aquitards.

PubMed

Puigserver, Diana; Herrero, Jofre; Torres, Mònica; Cortés, Amparo; Nijenhuis, Ivonne; Kuntze, Kevin; Parker, Beth L; Carmona, José M

2016-09-01

In the transition zone between aquifers and basal aquitards, the perchloroethene pools at an early time in their evolution are more recalcitrant than those elsewhere in the aquifer. The aim of this study is to demonstrate that the biodegradation of chloroethenes from aged pools (i.e., pools after decades of continuous groundwater flushing and dissolution) of perchloroethene is favored in the transition zone. A field site was selected where an aged pool exists at the bottom of a transition zone. Two boreholes were drilled to obtain sediment and groundwater samples to perform chemical, isotopic, molecular, and clone library analyses and microcosm experiments. The main results were as follows: (i) the transition zone is characterized by a high microbial richness; (ii) reductively dechlorinating microorganisms are present and partial reductive dechlorination coexists with denitrification, Fe and Mn reduction, and sulfate reduction; (iii) reductively dechlorinating microorganisms were also present in the zone of the aged pool; (v) the high concentrations of perchloroethene in this zone resulted in a decrease in microbial richness; (vi) however, the presence of fermenting microorganisms supplying electrons for the reductively dechlorinating microorganisms prevented the reductive dechlorination to be inhibited. These findings suggest that biostimulation and/or bioaugmentation could be applied to promote complete reductive dechlorination and to enhance the dissolution of more nonaqueous phase liquids (DNAPL).

Effect of trichloroethylene (TCE) toxicity on the enzymes of carbohydrate metabolism, brush border membrane and oxidative stress in kidney and other rat tissues.

PubMed

Khan, Sheeba; Priyamvada, Shubha; Khan, Sara A; Khan, Wasim; Farooq, Neelam; Khan, Farah; Yusufi, A N K

2009-07-01

Trichloroethylene (TCE), an industrial solvent, is a major environmental contaminant. Histopathological examinations revealed that TCE caused liver and kidney toxicity and carcinogenicity. However, biochemical mechanism and tissue response to toxic insult are not completely elucidated. We hypothesized that TCE induces oxidative stress to various rat tissues and alters their metabolic functions. Male Wistar rats were given TCE (1000 mg/kg/day) in corn oil orally for 25 d. Blood and tissues were collected and analyzed for various biochemical and enzymatic parameters. TCE administration increased blood urea nitrogen, serum creatinine, cholesterol and alkaline phosphatase but decreased serum glucose, inorganic phosphate and phospholipids indicating kidney and liver toxicity. Activity of hexokinase, lactate dehydrogenase increased in the intestine and liver whereas decreased in renal tissues. Malate dehydrogenase and glucose-6-phosphatase and fructose-1, 6-bisphosphatase decreased in all tissues whereas increased in medulla. Glucose-6-phosphate dehydrogenase increased but NADP-malic enzyme decreased in all tissues except in medulla. The activity of BBM enzymes decreased but renal Na/Pi transport increased. Superoxide dismutase and catalase activities variably declined whereas lipid peroxidation significantly enhanced in all tissues. The present results indicate that TCE caused severe damage to kidney, intestine, liver and brain; altered carbohydrate metabolism and suppressed antioxidant defense system.

Field-scale modeling of acidity production and remediation efficiency during in situ reductive dechlorination

NASA Astrophysics Data System (ADS)

Brovelli, A.; Robinson, C. E.; Barry, D. A.; Gerhard, J.

2009-12-01

Enhanced reductive dechlorination is a viable technology for in situ remediation of chlorinated solvent DNAPL source areas. Although in recent years increased understanding of this technology has led to more rapid dechlorination rates, complete dechlorination can be hindered by unfavorable conditions. Hydrochloric acid produced from dechlorination and organic acids generated from electron donor fermentation can lead to significant groundwater acidification. Adverse pH conditions can inhibit the activity of dehalogenating microorganisms and thus slow or stall the remediation process. The extent of acidification likely to occur at a contaminated site depends on a number of factors including (1) the extent of dechlorination, (2) the pH-sensitivity of dechlorinating bacteria, and (3) the geochemical composition of the soil and water, in particular the soil’s natural buffering capacity. The substantial mass of solvents available for dechlorination when treating DNAPL source zones means that these applications are particularly susceptible to acidification. In this study a reactive transport biogeochemical model was developed to investigate the chemical and physical parameters that control the build-up of acidity and subsequent remediation efficiency. The model accounts for the site water chemistry, mineral precipitation and dissolution kinetics, electron donor fermentation, gas phase formation, competing electron-accepting processes (e.g., sulfate and iron reduction) and the sensitivity of microbial processes to pH. Confidence in the model was achieved by simulating a well-documented field study, for which the 2-D field scale model was able to reproduce long-term variations of pH, and the concurrent build up of reaction products. Sensitivity analyses indicated the groundwater flow velocity is able to reduce acidity build-up when the rate of advection is comparable or larger than the rate of dechlorination. The extent of pH change is highly dependent on the presence of

Dechlorination of DDT, DDD and DDE in soil (slurry) phase using magnesium/palladium system.

PubMed

Gautam, Sumit Kumar; Suresh, Sumathi

2006-12-01

Mg0/Pd4+ was able to dechlorinate >99% of extractable DDT (initial concentration of 10 mg DDT kg(-1) of soil) and >90% of extractable DDT (initial concentration of 50 mg DDT kg(-1) of soil) in soil slurry. Mg0/Pd4+ was also found to be effective in dechlorinating of 50 mg kg(-1) DDD and DDE, in soil aged for varying time periods. GC-MS analyses revealed the formation of 1,1-diphenylethane as an end product from DDT, DDE and DDD. To the best of our knowledge this is the first report describing the application Mg0/Pd4+ system for remediation of DDT, DDD and DDE contaminated soil. We conclude that reductive dechlorination reaction catalyzed by Mg0/Pd4+ may be a promising system to remediate soil contaminated with DDT and its dechlorinated products such as DDD and DDE.

Improving the treatment of non-aqueous phase TCE in low permeability zones with permanganate.

PubMed

Chokejaroenrat, Chanat; Comfort, Steve; Sakulthaew, Chainarong; Dvorak, Bruce

2014-03-15

Treating dense non-aqueous phase liquids (DNAPLs) embedded in low permeability zones (LPZs) is a particularly challenging issue for injection-based remedial treatments. Our objective was to improve the sweeping efficiency of permanganate (MnO4(-)) into LPZs to treat high concentrations of TCE. This was accomplished by conducting transport experiments that quantified the penetration of various permanganate flooding solutions into a LPZ that was spiked with non-aqueous phase (14)C-TCE. The treatments we evaluated included permanganate paired with: (i) a shear-thinning polymer (xanthan); (ii) stabilization aids that minimized MnO2 rind formation and (iii) a phase-transfer catalyst. In addition, we quantified the ability of these flooding solutions to improve TCE destruction under batch conditions by developing miniature LPZ cylinders that were spiked with (14)C-TCE. Transport experiments showed that MnO4(-) alone was inefficient in penetrating the LPZ and reacting with non-aqueous phase TCE, due to a distinct and large MnO2 rind that inhibited the TCE from further oxidant contact. By including xanthan with MnO4(-), the sweeping efficiency increased (90%) but rind formation was still evident. By including the stabilization aid, sodium hexametaphosphate (SHMP) with xanthan, permanganate penetrated 100% of the LPZ, no rind was observed, and the percentage of TCE oxidized increased. Batch experiments using LPZ cylinders allowed longer contact times between the flooding solutions and the DNAPL and results showed that SHMP+MnO4(-) improved TCE destruction by ∼16% over MnO4(-) alone (56.5% vs. 40.1%). These results support combining permanganate with SHMP or SHMP and xanthan as a means of treating high concentrations of TCE in low permeable zones. Copyright © 2014 Elsevier B.V. All rights reserved.

Hexachlorobenzene dechlorination as affected by organic fertilizer and urea applications in two rice planted paddy soils in a pot experiment.

PubMed

Liu, C Y; Jiang, X; Yang, X L; Song, Y

2010-01-15

Reductive dechlorination is a crucial pathway for HCB degradation, the applications of organic materials and nitrogen can alter microbial activity and redox potential of soils, thus probably influence HCB dechlorination. To evaluate hexachlorobenzene (HCB) dechlorination as affected by organic fertilizer (OF) and urea applications in planted paddy soils, a pot experiment was conducted in two types of soils, Hydragric Acrisols (Ac) and Gleyi-Stagnic Anthrosols (An). After 18 weeks of experiment, HCB residues decreased by 28.2-37.5% of the initial amounts in Ac, and 42.1-70.9% in An. The amounts of HCB metabolites showed that dechlorination rates in An were higher than in Ac, which was mainly attributed to the higher pH and dissolved organic carbon (DOC) content of An. Both in Ac and An, the additions of 1% and 2% OF had negative effect on HCB dechlorination, which was probably because excessive nitrogen in OF decreased degraders' activity and the degradation of organic carbon in OF accepted electrons. The application of 0.03% urea could enhance HCB dechlorination rates slightly, while 0.06% urea accelerated HCB dechlorination significantly both in Ac and An. It could be assumed that urea served as an electron donor and stimulated degraders to dechlorinate HCB. In addition, the methanogenic bacteria were involved in dechlorination process, and reductive dechlorination in planted paddy soil might be impeded for the aerenchyma and O(2) supply into the rhizosphere. Results indicated that soil types, rice root system, methanogenic bacteria, OF and urea applications all had great effects on dechlorination process. Copyright 2009 Elsevier B.V. All rights reserved.

Reductive Dechlorination of Carbon Tetrachloride by Soil With Ferrous and Bisulfide

NASA Astrophysics Data System (ADS)

Choi, K.; Lee, W.

2008-12-01

Batch and column experiments were conducted to investigate the effect of concentration of reductants, contact time to activate reductive capacity, and pH on reductive dechlorination by soil with Fe(II) and HS- in this study. Carbon tetrachloride (CT) was used as a representative target organic compound. Sorption kinetic and isotherm tests were performed to investigate the influence of adsorption on the soil surface. Target compound in the soil suspension reached sorption equilibrium in 4 hours and the type of isotherm was well fitted by a linear type isotherm. In batch experiment, kinetic rate constants for the reductive dechlorination of CT increased with increasing the concentration of the reductants (Fe(II) and HS-). However, Fe(II) was a much more effective reductant, producing higher k values than those of HS-. The contact time of one day for the soil with HS- and that of four hours with Fe(II) showed the highest reaction rates. Additionally, the rate constants increased with the increase of pH in soil suspension with Fe(II) (5.2~8) and HS- (8.3~10.3), respectively. In column experiment, the soil column with Fe(II) showed larger bed volumes (13.76) to reach a column breakthrough than that with HS- indicating the treatment of Fe(II) is more effective for the reductive dechlorination of CT. To enhance reductive capacity of soil column under an acidic condition, CaO addition to the column treated with Fe(II) showed better results for the reductive dechlorination of CT than that of HS-. Fe(II) showed better CT dechlorination than HS- in batch and column reactors therefore, it can be used as an effective reducing agent for the treatment of soil contaminated with chlorinated organic compounds.

Trichloroethene (TCE) hydrodechlorination by NiFe nanoparticles: Influence of aqueous anions on catalytic pathways.

PubMed

Han, Yanlai; Liu, Changjie; Horita, Juske; Yan, Weile

2018-08-01

Amending bulk and nanoscale zero-valent iron (ZVI) with catalytic metals significantly accelerates hydrodechlorination of groundwater contaminants such as trichloroethene (TCE). The bimetallic design benefits from a strong synergy between Ni and Fe in facilitating the production of active hydrogen for TCE reduction, and it is of research and practical interest to understand the impacts of common groundwater solutes on catalyst and ZVI functionality. In this study, TCE hydrodechlorination reaction was conducted using fresh NiFe bimetallic nanoparticles (NiFe BNPs) and those aged in chloride, sulfate, phosphate, and humic acid solutions with concurrent analysis of carbon fractionation of TCE and its daughter products. The apparent kinetics suggest that the reactivity of NiFe BNPs is relatively stable in pure water and chloride or humic acid solutions, in contrast to significant deactivation observed of PdFe bimetallic particles in similar media. Exposure to phosphate at greater than 0.1 mM led to a severe decrease in TCE reaction rate. The change in kinetic regimes from first to zeroth order with increasing phosphate concentration is consistent with consumption of reactive sites by phosphate. Despite severe kinetic effect, there is no significant shift in TCE 13 C bulk enrichment factor between the fresh and the phosphate-aged particles. Instead, pronounced retardation of TCE reaction by NiFe BNPs in deuterated water (D 2 O) points to the importance of hydrogen spillover in controlling TCE reduction rate by NiFe BNPs, and such process can be strongly affected by groundwater chemistry. Copyright © 2018 Elsevier Ltd. All rights reserved.

The important role of polyvinylpyrrolidone and Cu on enhancing dechlorination of 2,4-dichlorophenol by Cu/Fe nanoparticles: Performance and mechanism study

NASA Astrophysics Data System (ADS)

Fang, Liping; Xu, Cuihong; Zhang, Wenbin; Huang, Li-Zhi

2018-03-01

The important role of polyvinylpyrrolidone (PVP) and Cu on the reductive dechlorination of 2,4-dichlorophenol (2,4-DCP) by Cu/Fe bimetal nanoparticles has been investigated. The synthesized PVP coated Cu/Fe bimetal nanoparticles with different Cu/Fe ratios were systematically characterized by FTIR, XRD, TEM and magnetic hysteresis loops. The Cu/Fe ratio and the PVP loading were optimized for dechlorination performance, and the optimum ratio of PVP to Cu/Fe was found to be 0.35 and the content of Cu in Cu/Fe nanoparticles was 41%. The presence of PVP as a dispersant/stabilizer results in a highly-dispersed Cu/Fe NPs and increase the reactivity of Cu/Fe NPs for 2,4-DCP removal. The dechlorination rate was enhanced at lower pH and higher temperature conditions. The presence of humic acid, PO43-, NO3-, SO42- leads to a slightly decreased removal efficiency of 2,4-DCP. The magnetic property of PVP-Cu/Fe nanoparticles allows rapid magnetic separation of the catalysts after reaction. A galvanic corrosion model was proposed where iron corrodes and transfers electrons to Cu-rich catalytic regions of the nanoparticles, and finally accelerating the reduction efficiency of 2,4-DCP.

Steam and air co-injection in removing residual TCE in unsaturated layered sandy porous media.

PubMed

Peng, Sheng; Wang, Ning; Chen, Jiajun

2013-10-01

Steam and air co-injection is a promising technique for volatile and semi-volatile organic contaminant remediation in heterogeneous porous media. In this study, removal of trichloroethene (TCE) with steam-air co-injection was investigated through a series of 2D sandbox experiments with different layered sand structures, and through numerical simulations. The results show that a layered structure with coarse sand, in which steam and air convection are relatively rapid, resulted in a higher removal rate and a larger removal ratio than those observed in an experiment using finer sand; however, the difference was not significant, and the removal ratios from three experiments ranged from 85% to 94%. Slight downward movement of TCE was observed for Experiment 1 (TCE initially in a fine sand zone encased in a coarse sand), while no such movement was observed for Experiment 2 (TCE initially in two fine sand layers encased in a coarse sand) or 3 (TCE initially in a silty sand zone encased in a coarse sand). Simulations show accumulation of TCE at the interface of the layered sands, which indicates a capillary barrier effect in restraining the downward movement of TCE. This effect is illustrated further by a numerical experiment with homogeneous coarse sand, in which continuous downward TCE movement to the bottom of the sandbox was simulated. Another numerical experiment with higher water saturation was also conducted. The results illustrate a complicated influence of water saturation on TCE removal in a layered sand structure. Published by Elsevier B.V.

TCE degradation in groundwater by chelators-assisted Fenton-like reaction of magnetite: Sand columns demonstration.

PubMed

Jia, Daqing; Sun, Sheng-Peng; Wu, Zhangxiong; Wang, Na; Jin, Yaoyao; Dong, Weiyang; Chen, Xiao Dong; Ke, Qiang

2018-03-15

Trichloroethylene (TCE) degradation in sand columns has been investigated to evaluate the potential of chelates-enhanced Fenton-like reaction with magnetite as iron source for in situ treatment of TCE-contaminated groundwater. The results showed that successful degradation of TCE in sand columns was obtained by nitrilotriacetic acid (NTA)-assisted Fenton-like reaction of magnetite. Addition of ethylenediaminedisuccinic acid (EDDS) resulted in an inhibitory effect on TCE degradation in sand columns. Similar to EDDS, addition of ethylenediaminetetraacetic acid (EDTA) also led to an inhibition of TCE degradation in sand column with small content of magnetite (0.5 w.t.%), but enhanced TCE degradation in sand column with high content of magnetite (7.0 w.t.%). Additionally, the presence of NTA, EDDS and EDTA greatly decreased H 2 O 2 uptake in sand columns due to the competition between chelates and H 2 O 2 for surface sites on magnetite (and sand). Furthermore, the presented results show that magnetite in sand columns remained stable in a long period operation of 230 days without significant loss of performance in terms of TCE degradation and H 2 O 2 uptake. Moreover, it was found that TCE was degraded mainly to formic acid and chloride ion, and the formation of chlorinated organic intermediates was minimal by this process. Copyright © 2017 Elsevier B.V. All rights reserved.

Bioelectrochemically-assisted reductive dechlorination of 1,2-dichloroethane by a Dehalococcoides-enriched microbial culture.

PubMed

Leitão, Patrícia; Rossetti, Simona; Nouws, Henri P A; Danko, Anthony S; Majone, Mauro; Aulenta, Federico

2015-11-01

The aim of this study was to verify the possibility to use a polarized graphite electrode as an electron donor for the reductive dechlorination of 1,2-dichloroethane, an ubiquitous groundwater contaminant. The rate of 1,2-DCA dechlorination almost linearly increased by decreasing the set cathode potential over a broad range of set cathode potentials (i.e., from -300 mV to -900 mV vs. the standard hydrogen electrode). This process was primarily dependent on electrolytic H2 generation. On the other hand, reductive dechlorination proceeded (although quite slowly) with a very high Coulombic efficiency (near 70%) at a set cathode potential of -300 mV, where no H2 production occurred. Under this condition, reductive dechlorination was likely driven by direct electron uptake from the surface of the polarized electrode. Taken as a whole, this study further extends the range of chlorinated contaminants which can be treated with bioelectrochemical systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

EFFECTS OF PH ON DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT IRON

EPA Science Inventory

The reduction rates of trichloroethylene (TCE) using zero-valent iron (ZVI) and the rates of iron hydrolysis were characterized at pH values of 5 to 10. The reduction of TCE by ZVI was carried out in batch reactors filled with pH-buffered (phosphate based) solutions under anaerob...

Formulation design for target delivery of iron nanoparticles to TCE zones.

PubMed

Wang, Ziheng; Acosta, Edgar

2013-12-01

Nanoparticles of zero-valent iron (NZVI) are effective reducing agents for some dense non-aqueous phase liquid (DNAPL) contaminants such as trichloroethylene (TCE). However, target delivery of iron nanoparticles to DNAPL zones in the aquifer remains an elusive feature for NZVI technologies. This work discusses three strategies to deliver iron nanoparticles to DNAPL zones. To this end, iron oxide nanoparticles coated with oleate (OL) ions were used as stable analogs for NZVI. The OL-coated iron oxide nanoparticles are rendered lipophilic via (a) the addition of CaCl2, (b) acidification, or (c) the addition of a cationic surfactant, benzethonium chloride (BC). Mixtures of OL and BC show promise as a target delivery strategy due to the high stability of the nanoparticles in water, and their preferential partition into TCE in batch experiments. Column tests show that while the OL-BC coated iron oxide nanoparticles remain largely mobile in TCE-free columns, a large fraction of these particles are retained in TCE-contaminated columns, confirming the effectiveness of this target delivery strategy. © 2013.

Geochemical and microbial community determinants of reductive dechlorination at a site biostimulated with glycerol.

PubMed

Atashgahi, Siavash; Lu, Yue; Zheng, Ying; Saccenti, Edoardo; Suarez-Diez, Maria; Ramiro-Garcia, Javier; Eisenmann, Heinrich; Elsner, Martin; J M Stams, Alfons; Springael, Dirk; Dejonghe, Winnie; Smidt, Hauke

2017-03-01

Biostimulation is widely used to enhance reductive dechlorination of chlorinated ethenes in contaminated aquifers. However, the knowledge on corresponding biogeochemical responses is limited. In this study, glycerol was injected in an aquifer contaminated with cis-dichloroethene (cDCE), and geochemical and microbial shifts were followed for 265 days. Consistent with anoxic conditions and sulfate reduction after biostimulation, MiSeq 16S rRNA gene sequencing revealed temporarily increased relative abundance of Firmicutes, Bacteriodetes and sulfate reducing Deltaproteobacteria. In line with 13 C cDCE enrichment and increased Dehalococcoides mccartyi (Dcm) numbers, dechlorination was observed toward the end of the field experiment, albeit being incomplete with accumulation of vinyl chloride. This was concurrent with (i) decreased concentrations of dissolved organic carbon (DOC), reduced relative abundances of fermenting and sulfate reducing bacteria that have been suggested to promote Dcm growth by providing electron donor (H 2 ) and essential corrinoid cofactors, (ii) increased sulfate concentration and increased relative abundance of Epsilonproteobacteria and Deferribacteres as putative oxidizers of reduced sulfur compounds. Strong correlations of DOC, relative abundance of fermenters and sulfate reducers, and dechlorination imply the importance of syntrophic interactions to sustain robust dechlorination. Tracking microbial and environmental parameters that promote/preclude enhanced reductive dechlorination should aid development of sustainable bioremediation strategies. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

RELATIONSHIP BETWEEN DEHALOCOCCOIDES DNA IN GROUND WATER AND RATES OF REDUCTIVE DECHLORINATION AT FIELD SCALE

EPA Science Inventory

Certain strains of Dehalococcodies bacteria can dechlorinate chlorinated ethylenes to harmless products. This study was conducted to determine if there is a valid association between the amount of DNA of Dehalococcodies sp. in ground water and useful rates of dechlorination in fi...

Experimental and theoretical investigation of vibrational spectra of coordination polymers based on TCE-TTF.

PubMed

Olejniczak, Iwona; Lapiński, Andrzej; Swietlik, Roman; Olivier, Jean; Golhen, Stéphane; Ouahab, Lahcène

2011-08-01

The room-temperature infrared and Raman spectra of a series of four isostructural polymeric salts of 2,3,6,7-tetrakis(2-cyanoethylthio)-tetrathiafulvalene (TCE-TTF) with paramagnetic (Co(II), Mn(II)) and diamagnetic (Zn(II), Cd(II)) ions, together with BF(4)(-) or ClO(4)(-) anions are reported. Infrared and Raman-active modes are identified and assigned based on theoretical calculations for neutral and ionized TCE-TTF using density functional theory (DFT) methods. It is confirmed that the TCE-TTF molecules in all the materials investigated are fully ionized and interact in the crystal structure through cyanoethylthio groups. The vibrational modes related to the C=C stretching vibrations of TCE-TTF are analyzed assuming the occurrence of electron-molecular vibration coupling (EMV). The presence of the antisymmetric C=C dimeric mode provides evidence that charge transfer takes place between TCE-TTF molecules belonging to neighboring polymeric networks. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Betula pendula: A Promising Candidate for Phytoremediation of TCE in Northern Climates.

PubMed

Lewis, Jeffrey; Qvarfort, Ulf; Sjöström, Jan

2015-01-01

Betula pendula (Silver birch) trees growing on two contaminated sites were evaluated to assess their capacity to phytoscreen and phytoremediate chlorinated aliphatic compounds and heavy metals. Both locations are industrially-contaminated properties in central Sweden. The first was the site of a trichloroethylene (TCE) spill in the 1980s while the second was polluted with heavy metals by burning industrial wastes. In both cases, sap and sapwood from Silver birch trees were collected and analyzed for either chlorinated aliphatic compounds or heavy metals. These results were compared to analyses of the surface soil, vadose zone pore air and groundwater. Silver birch demonstrated the potential to phytoscreen and possibly phytoremediate TCE and related compounds, but it did not demonstrate the ability to effectively phytoextract heavy metals when compared with hyperaccumulator plants. The capacity of Silver birch to phytoremediate TCE appears comparable to tree species that have been employed in field-scale TCE phytoremediation efforts, such as Populus spp. and Eucalyptus sideroxylon rosea.

Reactivity Of Substituted Chlorines And Ensuing Dechlorination Pathways Of Select PCB Congeners With Pd/Mg Bimetallics

EPA Science Inventory

Conflicting accounts occur on the reactivity of substituted chlorines and the ensuing dechlorination pathway of PCBs undergoing catalytic hydrodechlorination (HDCl). In order to understand these relationships, intermediates and dechlorination pathways of carefully selected 17 co...

Effects of Polychlorinated Biphenyl Congener Concentration and Sediment Supplementation on Rates of Methanogenesis and 2,3,6-Trichlorobiphenyl Dechlorination in an Anaerobic Enrichment

PubMed Central

Boyle, Alfred W.; Blake, Cheryl K.; Price, W. Allen; May, Harold D.

1993-01-01

We have employed a method of enrichment that allows us to significantly increase the rate of reductive polychlorinated biphenyl (PCB) dechlorination. This method shortens the time required to investigate the effects that culture conditions have on dechlorination and provides an estimate of the potential activity of the PCB-dechlorinating anaerobes. The periodic supplementation of sterile sediment and PCB produced an enhanced, measurable, and sustained rate of dechlorination. We observed volumetric rates of the dechlorination of 2,3,6-trichlorobiphenyl (2,3,6-CB) to 2,6-dichlorobiphenyl (2,6-CB) of more than 300 μmol liter-1 day-1 when the cultures were supplemented daily. A calculation of this activity that is based on an estimate of the number of dechlorinating anaerobes present indicates that 1.13 pmol of 2,3,6-CB was dechlorinated to 2,6-CB day-1 bacterial cell-1. This rate is similar to that of the reductive dechlorination of 3-chlorobenzoate by Desulfomonile tiedjei. Methanogenesis declined from 585.3 to 125.9 μmol of CH4 liter-1 day-1, while dechlorination increased from 8.2 to 346.0 μmol of 2,3,6-CB dechlorinated to 2,6-CB liter-1 day-1. PMID:16349045

RELATIONSHIP BETWEEN GEOCHEMICAL PARAMETERS AND THE OCCURRENCE OF DEHALOCOCCOIDES DNA IN CONTAMINATED AQUIFERS

EPA Science Inventory

Stains of Dehalococcoides are the only microbes known that can completely dechlorinate PCE, TCE, cis-DCE and vinyl chloride to ethylene. Either naturally-occurring strains or bioaugmentation cultures of Dehalococcoides are widely used for in situ bioremediation ...

Reductive dechlorination of polychlorinated biphenyls by zerovalent iron in subcritical water

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

Yak, H.K.; Wenclawiak, B.W.; Cheng, I.F.

1999-04-15

A method for remediation of PCB-contaminated soil and sediments is described that uses zerovalent iron as the dechlorination agent and subcritical water extraction (SWE) as the transporting medium. By using 100-mesh iron powder and SWE conditions of 250 C and 10 MPa on Aroclor 1260 for 1--8 h, the higher chlorine-substituted homologues were completely reduced to their lower substituted counterparts. The lower-substituted congeners were subsequently near-completely dechlorinated. The initial findings indicate that this technique may be a viable method for remediation of PCB-contaminated soil and sediments.

Hydrodechlorination of TCE in a circulated electrolytic column at high flow rate.

PubMed

Fallahpour, Noushin; Yuan, Songhu; Rajic, Ljiljana; Alshawabkeh, Akram N

2016-02-01

Palladium-catalytic hydrodechlorination of trichloroethylene (TCE) by cathodic H2 produced from water electrolysis has been tested. For a field in-well application, the flow rate is generally high. In this study, the performance of Pd-catalytic hydrodechlorination of TCE using cathodic H2 is evaluated under high flow rate (1 L min(-1)) in a circulated column system, as expected to occur in practice. An iron anode supports reduction conditions and it is used to enhance TCE hydrodechlorination. However, the precipitation occurs and high flow rate was evaluated to minimize its adverse effects on the process (electrode coverage, clogging, etc.). Under the conditions of 1 L min(-1) flow, 500 mA current, and 5 mg L(-1) initial TCE concentration, removal efficacy using iron anodes (96%) is significantly higher than by mixed metal oxide (MMO) anodes (66%). Two types of cathodes (MMO and copper foam) in the presence of Pd/Al2O3 catalyst under various currents (250, 125, and 62 mA) were used to evaluate the effect of cathode materials on TCE removal efficacy. The similar removal efficiencies were achieved for both cathodes, but more precipitation generated with copper foam cathode (based on the experiments done by authors). In addition to the well-known parameters such as current density, electrode materials, and initial TCE concentration, the high velocities of groundwater flow can have important implications, practically in relation to the flush out of precipitates. For potential field application, a cost-effective and sustainable in situ electrochemical process using a solar panel as power supply is being evaluated. Published by Elsevier Ltd.

Hydrodechlorination of TCE in a circulated electrolytic column at high flow rate

PubMed Central

Fallahpour, Noushin; Yuan, Songhu; Rajic, Ljiljana; Alshawabkeh, Akram N.

2015-01-01

Palladium-catalytic hydrodechlorination of trichloroethylene (TCE) by cathodic H2 produced from water electrolysis has been tested. For a field in-well application, the flow rate is generally high. In this study, the performance of Pd-catalytic hydrodechlorination of TCE using cathodic H2 is evaluated under high flow rate (1 L min−1) in a circulated column system, as expected to occur in practice. An iron anode supports reduction conditions and it is used to enhance TCE hydrodechlorination. However, the precipitation occurs and high flow rate was evaluated to minimize its advers effects on the process (electrode coverage, clogging, etc.). Under the conditions of 1 L min−1 flow, 500 mA current, and 5 mg L−1 initial TCE concentration, removal efficacy using iron anodes (96%) is significantly higher than by mixed metal oxide (MMO) anodes (66%). Two types of cathodes (MMO and copper foam) in the presence of Pd/Al2O3 catalyst under various currents (250, 125, and 62 mA) were used to evaluate the effect of cathode materials on TCE removal efficacy. The similar removal efficiencies were achieved for both cathodes, but more precipitation generated with copper foam cathode (based on the experiments done by authors). In addition to the well-known parameters such as current density, electrode materials, and initial TCE concentration, the high velocities of groundwater flow can have important implications, practically in relation to the flush out of precipitates. For potential field application, a cost-effective and sustainable in situ electrochemical process using a solar panel as power supply is being evaluated. PMID:26344148

EFFECTS OF PH ON DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT IRON

EPA Science Inventory

The surface normalized reaction rate constants (ksa) of trichloroethylene (TCE) and zero-valent iron (ZVI) was quantified in batch reactors at pH values between 1.7 and 10. The ksa of TCE linearly decreased from 0.044 to 0.009 L/hr-m2 between pH 3.8 and 8.0, whereas the ksa at pH...

Biochar as an electron shuttle for reductive dechlorination of pentachlorophenol by Geobacter sulfurreducens

PubMed Central

Yu, Linpeng; Yuan, Yong; Tang, Jia; Wang, Yueqiang; Zhou, Shungui

2015-01-01

The reductive dechlorination of pentachlorophenol (PCP) by Geobacter sulfurreducens in the presence of different biochars was investigated to understand how biochars affect the bioreduction of environmental contaminants. The results indicated that biochars significantly accelerate electron transfer from cells to PCP, thus enhancing reductive dechlorination. The promotion effects of biochar (as high as 24-fold) in this process depend on its electron exchange capacity (EEC) and electrical conductivity (EC). A kinetic model revealed that the surface redox-active moieties (RAMs) and EC of biochar (900 °C) contributed to 56% and 41% of the biodegradation rate, respectively. This work demonstrates that biochars are efficient electron mediators for the dechlorination of PCP and that both the EC and RAMs of biochars play important roles in the electron transfer process. PMID:26592958

Microbial dechlorination of polychlorinated biphenyls, dibenzo-p-dioxins, and -furans at the Portland Harbor Superfund site, Oregon, USA.

PubMed

Rodenburg, Lisa A; Krumins, Valdis; Curran, Joanna Crowe

2015-06-16

The Portland Harbor (Oregon, USA) has been declared a "Superfund" site because it is impacted by a variety of contaminants, including polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs). Using data collected in the remedial investigation, concentrations of PCBs and PCDD/Fs in sediment and water were examined using positive matrix factorization to look for evidence that PCBs and PCDD/Fs are dechlorinated by anaerobic bacteria. This process has long been known to occur in sediments. Recently, it has been recognized that PCB and PCDD/F dechlorination may also occur in other anaerobic environments, such as in landfills, sewers, and groundwater. The results indicate that a factor related to the dechlorination of PCBs and PCDD/Fs was present in the water but not in the sediment. Spatial patterns in dechlorination products suggest that they come primarily from groundwater. Dechlorination products comprise 22% of the PCBs in the water. The Portland Harbor therefore represents the third major US watershed in which PCBs appear to undergo dechlorination in an environment other than sediment, suggesting that the microbial dechlorination of PCBs and PCDD/Fs is more common than previously assumed. In addition, the Portland Harbor is impacted by PCBs generated inadvertently during the production of pigments, such as PCB 11, which alone exceeded the 64 pg/L federal water quality standard for the sum of PCBs in two of 120 whole water samples.

COMPLETE NATURAL ATTENUATION OF PCE AND TCE WITHOUT VINYL CHLORIDE AND ETHENE ACCUMULATION

EPA Science Inventory

A shallow aquifer at the Twin Cities Army Ammunition Plant (TCAAP) was contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE). Cisdichloroethylene (cis-DCE) is found in ground water at the site, indicating that reductive dehalogenation of PCE and TCE is occurrin...

MICROFRACTURE SURFACE GEOCHEMISTRY AND ADHERENT MICROBIAL POPULATION METABOLISM IN TCE-CONTAMINATED COMPETENT BEDROCK

EPA Science Inventory

A TCE-contaminated competent bedrock site in Portsmouth, NH was used to determine if a relation existed between microfracture (MF) surface geochemistry and the ecology and metabolic activity of attached microbes relative to terminal electron accepting processes (TEAPs) and TCE bi...

Influence of phosphate and copper on reductive dechlorination of thiobencarb in California rice field soils.

PubMed

Gunasekara, Amrith S; Tenbrook, Patti L; Palumbo, Amanda J; Johnson, Catherine S; Tjeerdema, Ronald S

2005-12-28

The potential for reductive dechlorination of the herbicide thiobencarb (TB) by microbes and its prevention in saturated anaerobic rice field soils was examined in laboratory microcosms. TB is effective in controlling both annual grasses and broadleaf weeds. In anoxic microcosms, TB was effectively degraded within 30 days to its dechlorinated product, deschlorothiobencarb (DTB), in two Sacramento Valley rice field soils. TB dechlorination, and subsequent degradation, followed pseudo-zero- (lag phase) and first-order (degradation phase) kinetics. Logistic regression analysis (r2 > 0.841) produced a half-life (t(1/2)) in nonsterile soils ranging from 10 to 15 days, which was also observed when microcosms were amended with low concentrations (<3 mg L(-1)) of copper (Cu2+; as the fungicides Cu(OH)2 and CuSO4.5H2O). High Cu2+ concentrations (>40 mg L(-1)) were added to the microcosms to determine if copper toxicity to dechlorinating microbes is concentration dependent within the range used. After 30 days, the low-copper-amended soils closely resembled the nonsterile experiments to which no Cu2+ was added while the high-copper-amended microcosms were similar to the sterile experiment. Microcosms were also separately amended with 5.7 g L(-1) phosphate (PO4(2-); as KH2PO4), a nutrient regularly applied to rice fields. Phosphate-amended experiments also showed TB degradation, but no DTB formation, indicating the phosphate played a role, possibly as a microbial inhibitor or an alternative electron acceptor, in limiting the dechlorination of TB. In summary, TB dechlorination was inhibited at high Cu(OH)2, CuSO4.5H2O, and KH2PO4 concentrations.

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

NASA Astrophysics Data System (ADS)

Badin, Alice; Broholm, Mette M.; Jacobsen, Carsten S.; Palau, Jordi; Dennis, Philip; Hunkeler, Daniel

2016-09-01

Thermal tetrachloroethene (PCE) remediation by steam injection in a sandy aquifer led to the release of dissolved organic carbon (DOC) from aquifer sediments resulting in more reduced redox conditions, accelerated PCE biodegradation, and changes in microbial populations. These changes were documented by comparing data collected prior to the remediation event and eight years later. Based on the premise that dual C-Cl isotope slopes reflect ongoing degradation pathways, the slopes associated with PCE and TCE suggest the predominance of biotic reductive dechlorination near the source area. PCE was the predominant chlorinated ethene near the source area prior to thermal treatment. After thermal treatment, cDCE became predominant. The biotic contribution to these changes was supported by the presence of Dehalococcoides sp. DNA (Dhc) and Dhc targeted rRNA close to the source area. In contrast, dual C-Cl isotope analysis together with the almost absent VC 13C depletion in comparison to cDCE 13C depletion suggested that cDCE was subject to abiotic degradation due to the presence of pyrite, possible surface-bound iron (II) or reduced iron sulphides in the downgradient part of the plume. This interpretation is supported by the relative lack of Dhc in the downgradient part of the plume. The results of this study show that thermal remediation can enhance the biodegradation of chlorinated ethenes, and that this effect can be traced to the mobilisation of DOC due to steam injection. This, in turn, results in more reduced redox conditions which favor active reductive dechlorination and/or may lead to a series of redox reactions which may consecutively trigger biotically induced abiotic degradation. Finally, this study illustrates the valuable complementary application of compound-specific isotopic analysis combined with molecular biology tools to evaluate which biogeochemical processes are taking place in an aquifer contaminated with chlorinated ethenes.

PCE/TCE DEGRADATION USING MULCH BIOWALLS

EPA Science Inventory

A passive reactive barrier (Biowall) was installed at the OU-1 site at Altus Air Force Base, Oklahoma to treat TCE contamination in ground water from a landfill. Depth to ground water varies from 1.8 to 2.4 meters below land surface. To intercept and treat the plume of contamin...

Dechlorination of lindane by the cyanobacterium Anabaena sp. strain PCC7120 depends on the function of the nir operon.

PubMed Central

Kuritz, T; Bocanera, L V; Rivera, N S

1997-01-01

Nitrate is essential for lindane dechlorination by the cyanobacteria Anabaena sp. strain PCC7120 and Nostoc ellipsosporum, as it is for dechlorination of other organic compounds by heterotrophic microorganisms. Based on analyses of mutants and effects of environmental factors, we conclude that lindane dechlorination by Anabaena sp. requires a functional nir operon that encodes the enzymes for nitrate utilization. PMID:9150239

Enhanced reductive dechlorination in columns treated with edible oil emulsion

NASA Astrophysics Data System (ADS)

Long, Cameron M.; Borden, Robert C.

2006-09-01

The effect of edible oil emulsion treatment on enhanced reductive dechlorination was evaluated in a 14 month laboratory column study. Experimental treatments included: (1) emulsified soybean oil and dilute HCl to inhibit biological activity; (2) emulsified oil only; (3) emulsified oil and anaerobic digester sludge; and (4) continuously feeding soluble substrate. A single application of emulsified oil was effective in generating strongly reducing, anaerobic conditions for over 14 months. PCE was rapidly reduced to cis-DCE in all three live columns. Bioaugmentation with a halorespiring enrichment culture resulted in complete dechlorination of PCE to ethene in the soluble substrate column (yeast extract and lactate). However, an additional treatment with a pulse of yeast extract and bioaugmentation culture was required to stimulate complete dechlorination in the emulsion treated columns. Once the dechlorinating population was established, the emulsion only column degraded PCE from 90-120 μM to below detection with concurrent ethene production in a 33 day contact time. The lower biodegradation rates in the emulsion treated columns compared to the soluble substrate column suggest that emulsified oil barriers may require a somewhat longer contact time for effective treatment. In the HCl inhibited column, partitioning of PCE to the retained oil substantially delayed PCE breakthrough. However, reduction of PCE to more soluble degradation products ( cis-DCE, VC and ethene) greatly reduced the impact of oil-water partitioning in live columns. There was only a small decline in the hydraulic conductivity ( K) of column #1 (low pH + emulsion, Kfinal/ Kinitial = 0.57) and column #2 (live + emulsion, Kfinal/ Kinitial = 0.73) indicating emulsion injection did not result in appreciable clogging of the clayey sand. However, K loss was greater in column #3 (sludge +emulsion, Kfinal/ Kinitial = 0.12) and column #4 (soluble substrate, Kfinal/ Kinitial = 0.03) indicating clogging due

Enhanced Fenton-like degradation of TCE in sand suspensions with magnetite by NTA/EDTA at circumneutral pH.

PubMed

Wang, Na; Jia, Daqing; Jin, Yaoyao; Sun, Sheng-Peng; Ke, Qiang

2017-07-01

The present study investigated the degradation of trichloroethylene (TCE) in sand suspensions by Fenton-like reaction with magnetite (Fe 3 O 4 ) in the presence of various chelators at circumneutral pH. The results showed that ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) greatly improved the rate of TCE degradation, while [S,S]-ethylenediaminedisuccinic acid (s,s-EDDS), malonate, citrate, and phytic acid (IP6) have minimal effects on TCE degradation. Quenching tests suggested that TCE was mainly degraded by hydroxyl radical (HO · ) attack, with about 90% inhibition on TCE degradation by the addition of HO · scavenger 2-propanol. The presence of 0.1-0.5% Fe 3 O 4 /sand (w/w) contributed to 40% increase in TCE degradation rates. In particular, the use of chelators can avoid high concentrations of H 2 O 2 required for the Fenton-like reaction with Fe 3 O 4 , and moreover improve the stoichiometric efficiencies of TCE degradation to H 2 O 2 consumption. The suitable concentrations of chelators (EDTA and NTA) and H 2 O 2 were suggested to be 0.5 and 20 mM, respectively. Under the given conditions, degradation rate constants of TCE were obtained at 0.360 h -1 with EDTA and 0.526 h -1 with NTA, respectively. Enhanced degradation of TCE and decreased usage of H 2 O 2 in this investigation suggested that Fenton-like reaction of Fe 3 O 4 together with NTA (or EDTA) may be a promising process for remediation of TCE-contaminated groundwater.

[Effects of copper on biodegradation mechanism of trichloroethylene by mixed microorganisms].

PubMed

Gao, Yanhui; Zhao, Tiantao; Xing, Zhilin; He, Zhi; Zhang, Lijie; Peng, Xuya

2016-05-25

We isolated and enriched mixed microorganisms SWA1 from landfill cover soils supplemented with trichloroethylene (TCE). The microbial mixture could degrade TCE effectively under aerobic conditions. Then, we investigated the effect of copper ion (0 to 15 μmol/L) on TCE biodegradation. Results show that the maximum TCE degradation speed was 29.60 nmol/min with 95.75% degradation when copper ion was at 0.03 μmol/L. In addition, genes encoding key enzymes during biodegradation were analyzed by Real-time quantitative reverse transcription PCR (RT-qPCR). The relative expression abundance of pmoA gene (4.22E-03) and mmoX gene (9.30E-06) was the highest when copper ion was at 0.03 μmol/L. Finally, we also used MiSeq pyrosequencing to investigate the diversity of microbial community. Methylocystaceae that can co-metabolic degrade TCE were the dominant microorganisms; other microorganisms with the function of direct oxidation of TCE were also included in SWA1 and the microbial diversity decreased significantly along with increasing of copper ion concentration. Based on the above results, variation of copper ion concentration affected the composition of SWA1 and degradation mechanism of TCE. The degradation mechanism of TCE included co-metabolism degradation of methanotrophs and oxidation metabolism directly at copper ion of 0.03 μmol/L. When copper ion at 5 μmol/L (biodegradation was 84.75%), the degradation mechanism of TCE included direct-degradation and co-metabolism degradation of methanotrophs and microorganisms containing phenol hydroxylase. Therefore, biodegradation of TCE by microorganisms was a complicated process, the degradation mechanism included co-metabolism degradation of methanotrophs and bio-oxidation of non-methanotrophs.

Reductive transformation of dioxins: An assessment of the contribution of dissolved organic matter to dechlorination reactions

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

Fu, Q.S.; Barkovskii, A.L.; Adriaens, P.

1999-11-01

The susceptibility of dioxins to dissolved organic carbon (DOC)-mediated dechlorination reactions was investigated using 1,2,3,4,6,7,9-heptachlorodibenzo-p-dioxin (HpCDD), Aldrich humic acid (AHA), and polymaleic acid (PMA) as model compounds. The dechlorination yields were on the order of 4--20% which, when normalized to phenolic acidity, was comparable to yields observed in the presence of the humic constituents catechol and resorcinol. Based on the ratio of dechlorination yields as a function of phenolic acidity and electron transfer capacity, differences in electron transfer efficiency to dioxins are likely combined effects of specific interactions with the functional groups and nonspecific hydrophobic interactions. Hexa- and pentaCDD homologuesmore » were dominant in all incubations, and diCDD constituted the final product of dechlorination. The rates of appearance of lesser chlorinated products were similar to those observed in sediment systems and followed thermodynamic considerations as they decreased with a decrease in level of chlorination. Generally, both absolute and phenolic acidity-normalized rate constants for AHA-mediated reactions were up to 2-fold higher than those effected by PMA. These results indicate that the electron shuttling capacity of sediment DOC may significantly affect the fate of dioxins, in part through dechlorination reactions.« less

[Electrochemically reductive dechlorination of chloroform in aqueous medium by codeposited palladium-nickel glassy carbon as cathode].

PubMed

Sun, Zhi-Rong; Li, Bao-Hua; Hu, Xiang; Shi, Min; Peng, Yong-Zhen

2008-05-01

The electrochemical deposition behaviors of Pd-Ni bimetal on glassy carbon (GC) electrode were studied by means of cyclic voltammetry (CV) based on orthogonal experiments. CV results reveal that Pd-Ni bimetal shows larger hydrogen adsorption peak than that of single Pd or Ni. The mixture of Ni2+ and Pd2+ can get hydrogen adsorption peak of -24.83 mA at - 500 mV (vs Hg/Hg2SO4). Scanning Electron Microscope (SEM) images reveal that nickel addition changes the distributing configuration of Pd microparticles on GC. And the appearance of Pd-Ni bimetal microparticles is distinctly different from that of single Pd and single Ni microparticles. Diameter of Pd-Ni microparticle is bigger than that of Pd microparticle and smaller than that of Ni microparticle. Effects of dechlorination current and time on removal efficiency of chloroform were also studied. The removal efficiency of chloroform increases at higher dechlorination current and longer dechlorination time. It reaches 42.53% when the dechlorination current and time are 0.5 mA and 180 min respectively on Pd-Ni/GC electrode prepared at optimum conditions. It can be envisioned that the removal efficiency of chloroform would increase further at longer dechlorination time.

Pentachlorophenol dechlorination with zero valent iron: a Raman and GCMS study of the complex role of surficial iron oxides.

PubMed

Gunawardana, Buddhika; Swedlund, Peter J; Singhal, Naresh; Nieuwoudt, Michel K

2018-04-20

The dechlorination of chlorinated organic pollutants by zero valent iron (ZVI) is an important water treatment process with a complex dependence on many variables. This complexity means that there are reported inconsistencies in terms of dechlorination with ZVI and the effect of ZVI acid treatment, which are significant and are as yet unexplained. This study aims to decipher some of this complexity by combining Raman spectroscopy with gas chromatography-mass spectrometry (GC-MS) to investigate the influence of the mineralogy of the iron oxide phases on the surface of ZVI on the reductive dechlorination of pentachlorophenol (PCP). Two electrolytic iron samples (ZVI-T and ZVI-H) were found to have quite different PCP dechlorination reactivity in batch reactors under anoxic conditions. Raman analysis of the "as-received" ZVI-T indicated the iron was mainly covered with the ferrous oxide (FeO) wustite, which is non-conducting and led to a low rate of PCP dechlorination. In contrast, the dominant oxide on the "as-received" ZVI-H was magnetite which is conducting and, compared to ZVI-T, the ZVI-H rate of PCP dechlorination was four times faster. Treating the ZVI-H sample with 1 N H 2 SO 4 made small change to the composition of the oxide layers and also minute change to the rate of PCP dechlorination. However, treating the ZVI-T sample with H 2 SO 4 led to the loss of wustite so that magnetite became the dominant oxide and the rate of PCP dechlorination increased to that of the ZVI-H material. In conclusion, this study clearly shows that iron oxide mineralogy can be a contributing factor to apparent inconsistencies in the literature related to ZVI performance towards dechlorination and the effect of acid treatment on ZVI reactivity.

Decision Tree based Prediction and Rule Induction for Groundwater Trichloroethene (TCE) Pollution Vulnerability

NASA Astrophysics Data System (ADS)

Park, J.; Yoo, K.

2013-12-01

For groundwater resource conservation, it is important to accurately assess groundwater pollution sensitivity or vulnerability. In this work, we attempted to use data mining approach to assess groundwater pollution vulnerability in a TCE (trichloroethylene) contaminated Korean industrial site. The conventional DRASTIC method failed to describe TCE sensitivity data with a poor correlation with hydrogeological properties. Among the different data mining methods such as Artificial Neural Network (ANN), Multiple Logistic Regression (MLR), Case Base Reasoning (CBR), and Decision Tree (DT), the accuracy and consistency of Decision Tree (DT) was the best. According to the following tree analyses with the optimal DT model, the failure of the conventional DRASTIC method in fitting with TCE sensitivity data may be due to the use of inaccurate weight values of hydrogeological parameters for the study site. These findings provide a proof of concept that DT based data mining approach can be used in predicting and rule induction of groundwater TCE sensitivity without pre-existing information on weights of hydrogeological properties.

PCE dechlorination by non-Dehalococcoides in a microbial electrochemical system.

PubMed

Yu, Jaecheul; Park, Younghyun; Nguyen, Van Khanh; Lee, Taeho

2016-08-01

The bioremediation of tetrachloroethene (perchloroethene; PCE) contaminated sites generally requires a supply of some fermentable organic substrates as an electron donor. On the other hand, organic substrates can induce the massive growth of microorganisms around the injection wells, which can foul the contaminated subsurface environment. In this study, PCE dechlorination to ethene was performed in a microbial electrochemical system (MES) using the electrode (a cathode polarized at -500 mV vs. standard hydrogen electrode) as the electron donor. Denaturing gel gradient electrophoresis and pyrosequencing revealed a variety of non-Dehalococcoides bacteria dominant in MES, such as Acinetobacter sp. (25.7 % for AS1 in suspension of M3), Rhodopseudomonas sp. (10.5 % for AE1 and 10.1 % for AE2 in anodic biofilm of M3), Pseudomonas aeruginosa (22.4 % for BS1 in suspension of M4), and Enterobacter sp. (21.7 % for BE1 in anodic biofilm of M4) which are capable of electron transfer, hydrogen production and dechlorination. The Dehalococcoides group, however, was not detected in this system. Therefore, these results suggest that a range of bacterial species outside the Dehalococcoides can play an important role in the microbial electrochemical dechlorination process, which may lead to innovative bioremediation technology.

Inhibitory Effects of Sulfate and Nitrate Reduction on Reductive Dechlorination of PCP in a Flooded Paddy Soil

PubMed Central

Xu, Yan; Xue, Lili; Ye, Qi; Franks, Ashley E.; Zhu, Min; Feng, Xi; Xu, Jianming; He, Yan

2018-01-01

Pentachlorophenol (PCP) is highly toxic and persistent in soils. Bioreduction of PCP often co-occurs with varying concentrations of sulfate and nitrate in flooded paddy soils where each can act as an electron acceptor. Anaerobic soil microcosms were constructed to evaluate the influence of sulfate and nitrate amendments and their redox processes. Microcosms with varying sulfate and nitrate concentrations demonstrated an inhibitory effect on reductive dechlorination of PCP compared to an untreated control. Compared to nitrate, sulfate exhibited a more significant impact on PCP dechlorination, as evidenced by a lower maximum reaction rate and a longer time to reach the maximum reaction rate. Dechlorination of PCP was initiated at the ortho-position, and then at the para- and meta-positions to form 3-CP as the final product in all microcosms. Deep sequencing of microbial communities in the microcosms revealed a strong variation in bacterial taxon among treatments. Specialized microbial groups, such as the genus of Desulfovibrio responding to the addition of sulfate, had a potential to mediate the competitive microbial dechlorination of PCP. Our results provide an insight into the competitive microbial-mediated reductive dechlorination of PCP in natural flooded soil or sediment environments. PMID:29643842

Chemostat Studies of TCE-Dehalogenating Anaerobic Consortia under Excess and Limited Electron Donor Addition

NASA Astrophysics Data System (ADS)

Semprini, L.; Azizian, M.; Green, J.; Mayer-Blackwell, K.; Spormann, A. M.

2015-12-01

Two cultures - the Victoria Strain (VS) and the Evanite Strain (EV), enriched with the organohalide respiring bacteria Dehalococcoides mccartyi - were grown in chemostats for more than 4 years at a mean cell residence time of 50 days. The slow doubling rate represents growth likely experienced in the subsurface. The chemostats were fed formate as an electron donor and trichloroethene (TCE) as the terminal electron acceptor. Under excess formate conditions, stable operation was observed with respect to TCE transformation, steady-state hydrogen (H2) concentrations (40 nM), and the structure of the dehalogenating community. Both cultures completely transformed TCE to ethene, with minor amounts of vinyl chloride (VC) observed, along with acetate formation. When formate was limited, TCE was transformed incompletely to ethene (40-60%) and VC (60- 40%), and H2 concentrations ranged from 1 to 3 nM. The acetate concentration dropped below detection. Batch kinetic studies of TCE transformation with chemostat harvested cells found transformation rates of c-DCE and VC were greatly reduced when the cells were grown with limited formate. Upon increasing formate addition to the chemostats, from limited to excess, essentially complete transformation of TCE to ethene was achieved. The increase in formate was associated with an increase in H2 concentration and the production of acetate. Results of batch kinetic tests showed increases in transformation rates for TCE and c-DCE by factors of 3.5 and 2.5, respectively, while VC rates increased by factors of 33 to 500, over a six month period. Molecular analysis of chemostat samples is being performed to quantify the changes in copy numbers of reductase genes and to determine whether shifts in the strains of Dehalococcoides mccartyi where responsible for the observed rate increases. The results demonstrate the importance of electron donor supply for successful in-situ remediation.

Laboratory-scale column study for remediation of TCE-contaminated aquifers using three-section controlled-release potassium permanganate barriers.

PubMed

Yuan, Baoling; Li, Fei; Chen, Yanmei; Fu, Ming-Lai

2013-05-01

A laboratory-scale study with a sand column was designed to simulate trichloroethylene (TCE) pollution in the aquifer environment with three-section controlled-release potassium permanganate (CRP) barriers. The main objective of this study was to evaluate the feasibility of CRP barriers in remediation of TCE in aquifers in a long-term and controlled manner. CRP particles with a 1:3 molar ratio of KMnO4 to stearic acid showed the best controlled-release properties in pure water, and the theoretical release time was 138.5 days. The results of TCE removal in the test column indicated that complete removal efficiency of TCE in a sand column by three-section CRP barriers could be reached within 15 days. The molar ratio of KMnO4 to TCE in the three-section CRP barriers was 16:1, which was much lower than 82:1 as required when KMnO4 solution is used directly to achieve complete destruction of TCE. This result revealed that the efficiency of CRP for remediation of TCE was highly improved after encapsulation.

Biodegradation of trichloroethylene and involvement of an aromatic biodegradative pathway.

PubMed Central

Nelson, M J; Montgomery, S O; Mahaffey, W R; Pritchard, P H

1987-01-01

Biodegradation of trichloroethylene (TCE) by bacterial strain G4 resulted in complete dechlorination of the compound, as indicated by the production of inorganic chloride. A component of the water from which strain G4 was isolated that was required for TCE degradation was identified as phenol. Strain G4 degraded TCE in the presence of chloramphenicol only when preinduced with phenol. Toluene, o-cresol. and m-cresol could replace the phenol requirement. Two of the inducers of TCE metabolism, phenol and toluene, apparently induced the same aromatic degradative pathway that cleaved the aromatic ring by meta fission. Cells induced with either phenol or toluene had similar oxidation rates for several aromatic compounds and had similar levels of catechol-2,3-dioxygenase. The results indicate that one or more enzymes of an inducible pathway for aromatic degradation in strain G4 are responsible for the degradation of TCE. PMID:3606099

Analysis of trichloroethylene removal and bacterial community function based on pH-adjusted in an upflow anaerobic sludge blanket reactor.

PubMed

Zhang, Ying; Hu, Miao; Li, Pengfei; Wang, Xin; Meng, Qingjuan

2015-11-01

The study reported the upflow anaerobic sludge blanket (UASB) reactor performance in treating wastewater containing trichloroethylene (TCE) and characterized variations of bacteria composition and structure by changing the pH from 6.0 to 8.0. A slightly acidic environment (pH < 7.0) had a greater impact on the TCE removal. Illumina pyrosequencing was applied to investigate the bacterial community changes in response to pH shifts. The results demonstrated that pH greatly influenced the dominance and presence of specific populations. The potential TCE degradation pathway in the UASB reactor was proposed. Importantly, the genus Dehalobacter which was capable of reductively dechlorinating TCE was detected, and it was not found at pH of 6.0, which presumably is the reason why the removal efficiency of TCE was the lowest (80.73 %). Through Pearson correlation analyses, the relative abundance of Dehalobacter positively correlated with TCE removal efficiency (R = 0.912). However, the relative abundance of Lactococcus negatively correlated with TCE removal efficiency according to the results from Pearson correlation analyses and redundancy analysis (RDA).

Reduction of trichloroethylene and nitrate by zero-valent iron with peat.

PubMed

Min, Jee-Eun; Kim, Meejeong; Pardue, John H; Park, Jae-Woo

2008-02-01

The feasibility of using zero-valent iron (ZVI) and peat mixture as in situ barriers for contaminated sediments and groundwater was investigated. Trichloroethylene (TCE) and nitrate (NO(3)(-)), redox sensitive contaminants were reduced by ZVI and peat soil mixture under anaerobic condition. Peat was used to support the sorption of TCE, microbial activity for biodegradation of TCE and denitrification while TCE and nitrate were reduced by ZVI. Decreases in TCE concentrations were mainly due to ZVI, while peat supported denitrifying microbes and further affected the sorption of TCE. Due to the competition of electrons, nitrate reduction was inhibited by TCE, while TCE reduction was not affected by nitrate. From the results of peat and sterilized peat, it can be concluded that peat was involved in both dechlorination and denitrification but biological reduction of TCE was negligible compared to that of nitrate. The results from hydrogen and methane gas analyses confirmed that hydrogen utilization by microbes and methanogenic process had occurred in the ZVI-peat system. Even though effect of the peat on TCE reduction were quantitatively small, ZVI and peat contributed to the removal of TCE and nitrate independently. The 16S rRNA analysis revealed that viable bacterial diversity was narrow and the most frequently observed genera were Bacillus and Staphylococcus spp.

Characterization of a Defined 2,3,5,6-Tetrachlorobiphenyl-ortho-Dechlorinating Microbial Community by Comparative Sequence Analysis of Genes Coding for 16S rRNA

PubMed Central

Pulliam Holoman, Tracey R.; Elberson, Margaret A.; Cutter, Leah A.; May, Harold D.; Sowers, Kevin R.

1998-01-01

Defined microbial communities were developed by combining selective enrichment with molecular monitoring of total community genes coding for 16S rRNAs (16S rDNAs) to identify potential polychlorinated biphenyl (PCB)-dechlorinating anaerobes that ortho dechlorinate 2,3,5,6-tetrachlorobiphenyl. In enrichment cultures that contained a defined estuarine medium, three fatty acids, and sterile sediment, a Clostridium sp. was predominant in the absence of added PCB, but undescribed species in the δ subgroup of the class Proteobacteria, the low-G+C gram-positive subgroup, the Thermotogales subgroup, and a single species with sequence similarity to the deeply branching species Dehalococcoides ethenogenes were more predominant during active dechlorination of the PCB. Species with high sequence similarities to Methanomicrobiales and Methanosarcinales archaeal subgroups were predominant in both dechlorinating and nondechlorinating enrichment cultures. Deletion of sediment from PCB-dechlorinating enrichment cultures reduced the rate of dechlorination and the diversity of the community. Substitution of sodium acetate for the mixture of three fatty acids increased the rate of dechlorination, further reduced the community diversity, and caused a shift in the predominant species that included restriction fragment length polymorphism patterns not previously detected. Although PCB-dechlorinating cultures were methanogenic, inhibition of methanogenesis and elimination of the archaeal community by addition of bromoethanesulfonic acid only slightly inhibited dechlorination, indicating that the archaea were not required for ortho dechlorination of the congener. Deletion of Clostridium spp. from the community profile by addition of vancomycin only slightly reduced dechlorination. However, addition of sodium molybdate, an inhibitor of sulfate reduction, inhibited dechlorination and deleted selected species from the community profiles of the class Bacteria. With the exception of one 16S r

Dechlorination of Hexachlorobenzene in Contaminated Soils Using a Nanometallic Al/CaO Dispersion Mixture: Optimization through Response Surface Methodology

PubMed Central

Jiang, Yuhui; Shang, Yixuan; Yu, Shuyao; Liu, Jianguo

2018-01-01

Hexachlorobenzene (HCB) contamination of soils remains a significant environmental challenge all over the world. Reductive stabilization is a developing technology that can decompose the HCB with a dechlorination process. A nanometallic Al/CaO (n-Al/CaO) dispersion mixture was developed utilizing ball-milling technology in this study. The dechlorination efficiency of HCB in contaminated soils by the n-Al/CaO grinding treatment was evaluated. Response surface methodology (RSM) was employed to investigate the effects of three variables (soil moisture content, n-Al/CaO dosage and grinding time) and the interactions between these variables under the Box-Behnken Design (BBD). A high regression coefficient value (R2 = 0.9807) and low p value (<0.0001) of the quadratic model indicated that the model was accurate in predicting the experimental results. The optimal soil moisture content, n-Al/CaO dosage, and grinding time were found to be 7% (m/m), 17.7% (m/m), and 24 h, respectively, in the experimental ranges and levels. Under optimal conditions, the dechlorination efficiency was 80%. The intermediate product analysis indicated that dechlorination was the process by stepwise loss of chloride atoms. The main pathway observed within 24 h was HCB → pentachlorobenzene (PeCB) → 1,2,3,4-tetrachlorobenzene (TeCB) and 1,2,4,5-TeCB. The results indicated that the moderate soil moisture content was crucial for the hydrodechlorination of HCB. A probable mechanism was proposed wherein water acted like a hydrogen donor and promoted the hydrodechlorination process. The potential application of n-Al/CaO is an environmentally-friendly and cost-effective option for decontamination of HCB-contaminated soils. PMID:29702570

Dechlorination of Hexachlorobenzene in Contaminated Soils Using a Nanometallic Al/CaO Dispersion Mixture: Optimization through Response Surface Methodology.

PubMed

Jiang, Yuhui; Shang, Yixuan; Yu, Shuyao; Liu, Jianguo

2018-04-27

Hexachlorobenzene (HCB) contamination of soils remains a significant environmental challenge all over the world. Reductive stabilization is a developing technology that can decompose the HCB with a dechlorination process. A nanometallic Al/CaO (n-Al/CaO) dispersion mixture was developed utilizing ball-milling technology in this study. The dechlorination efficiency of HCB in contaminated soils by the n-Al/CaO grinding treatment was evaluated. Response surface methodology (RSM) was employed to investigate the effects of three variables (soil moisture content, n-Al/CaO dosage and grinding time) and the interactions between these variables under the Box-Behnken Design (BBD). A high regression coefficient value ( R ² = 0.9807) and low p value (<0.0001) of the quadratic model indicated that the model was accurate in predicting the experimental results. The optimal soil moisture content, n-Al/CaO dosage, and grinding time were found to be 7% (m/m), 17.7% (m/m), and 24 h, respectively, in the experimental ranges and levels. Under optimal conditions, the dechlorination efficiency was 80%. The intermediate product analysis indicated that dechlorination was the process by stepwise loss of chloride atoms. The main pathway observed within 24 h was HCB → pentachlorobenzene (PeCB) → 1,2,3,4-tetrachlorobenzene (TeCB) and 1,2,4,5-TeCB. The results indicated that the moderate soil moisture content was crucial for the hydrodechlorination of HCB. A probable mechanism was proposed wherein water acted like a hydrogen donor and promoted the hydrodechlorination process. The potential application of n-Al/CaO is an environmentally-friendly and cost-effective option for decontamination of HCB-contaminated soils.

Characterization of a Highly Enriched Microbial Consortium Reductively Dechlorinating 2,3-Dichlorophenol and 2,4,6-Trichlorophenol and the Corresponding cprA Genes from River Sediment.

PubMed

El-Sayed, Wael S

2016-08-26

Anaerobic reductive dechlorination of 2,3-dichlorophenol (2,3DCP) and 2,4,6-trichlorophenol (2,4,6TCP) was investigated in microcosms from River Nile sediment. A stable sediment-free anaerobic microbial consortium reductively dechlorinating 2,3DCP and 2,4,6TCP was established. Defined sediment-free cultures showing stable dechlorination were restricted to ortho chlorine when enriched with hydrogen as the electron donor, acetate as the carbon source, and either 2,3-DCP or 2,4,6-TCP as electron acceptors. When acetate, formate, or pyruvate were used as electron donors, dechlorination activity was lost. Only lactate can replace dihydrogen as an electron donor. However, the dechlorination potential was decreased after successive transfers. To reveal chlororespiring species, the microbial community structure of chlorophenol-reductive dechlorinating enrichment cultures was analyzed by PCR-denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. Eight dominant bacteria were detected in the dechlorinating microcosms including members of the genera Citrobacter, Geobacter, Pseudomonas, Desulfitobacterium, Desulfovibrio and Clostridium. Highly enriched dechlorinating cultures were dominated by four bacterial species belonging to the genera Pseudomonas, Desulfitobacterium, and Clostridium. Desulfitobacterium represented the major fraction in DGGE profiles indicating its importance in dechlorination activity, which was further confirmed by its absence resulting in complete loss of dechlorination. Reductive dechlorination was confirmed by the stoichiometric dechlorination of 2,3DCP and 2,4,6TCP to metabolites with less chloride groups and by the detection of chlorophenol RD cprA gene fragments in dechlorinating cultures. PCR amplified cprA gene fragments were cloned and sequenced and found to cluster with the cprA/pceA type genes of Dehalobacter restrictus.

RATE OF TCE DEGRADATION IN PASSIVE REACTIVE BARRIERS CONSTRUCTED WITH PLANT MULCH (BIOWALLS)

EPA Science Inventory

This presentation reviews a case study at Altus AFB on the extent of treatment of TCE in a passive reactive barrier constructed with plant mulch. It presents data from a tracer test to estimate the rate of ground water flow at the site, and the residence time of water and TCE in...

A study on radiation technological degradation of organic chloride wastewater--exemplified by TCE and PCE.

PubMed

Huang, Sheng-Kai; Hsieh, Ling-Ling; Chen, Chia-Chieh; Lee, Po-Hsiu; Hsieh, Bor-Tsung

2009-01-01

This paper describes the potential of using gamma radiation technology to degrade trichloroethylene (TCE) and perchloroethylene (PCE) wastewater. The experimental method is divided into two parts: (1) using the gamma-ray to irradiate the TCE and PCE solution, the dose-rate is 10Gy/minute, the irradiation dosage is 0-2.5kGy and (2) self-making the UV irradiation system, the tube specification is 254nm and 6W, and turning on 8 tubes at the same time to make the irradiation. The efficiency of degradation ratio for gamma-ray is better than UV in the range of 0.1-250ppm; for example, as for the concentration of 0.1ppm, when TCE is degraded to D(90) and T(90), the gamma-ray only needed 46.7Gy and took about 4.67 minutes, but UV needed to take about 28.1 minutes. The dose-concentration equations of TCE and PCE are: TCE: y=44.58+8.832x, R(2)=0.999; and PCE: y=81.33+12.81x, R(2)=0.997. We verified that the radiation technology is able to effectively degrade the organic chlorine wastewater without yielding the secondary pollution, and the TCE and PCE that degraded by using gamma-ray will be reached US-EPA and Taiwan Effluent Standard (5ppb).

PCB dechlorination hotspots and reductive dehalogenase genes in sediments from a contaminated wastewater lagoon.

PubMed

Mattes, Timothy E; Ewald, Jessica M; Liang, Yi; Martinez, Andres; Awad, Andrew; Richards, Patrick; Hornbuckle, Keri C; Schnoor, Jerald L

2017-08-12

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants that are distributed worldwide. Although industrial PCB production has stopped, legacy contamination can be traced to several different commercial mixtures (e.g., Aroclors in the USA). Despite their persistence, PCBs are subject to naturally occurring biodegradation processes, although the microbes and enzymes involved are poorly understood. The biodegradation potential of PCB-contaminated sediments in a wastewater lagoon located in Virginia (USA) was studied. Total PCB concentrations in sediments ranged from 6.34 to 12,700 mg/kg. PCB congener profiles in sediment sample were similar to Aroclor 1248; however, PCB congener profiles at several locations showed evidence of dechlorination. The sediment microbial community structure varied among samples but was dominated by Proteobacteria and Firmicutes. The relative abundance of putative dechlorinating Chloroflexi (including Dehalococcoides sp.) was 0.01-0.19% among the sediment samples, with Dehalococcoides sp. representing 0.6-14.8% of this group. Other possible PCB dechlorinators present included the Clostridia and the Geobacteraceae. A PCR survey for potential PCB reductive dehalogenase genes (RDases) yielded 11 sequences related to RDase genes in PCB-respiring Dehalococcoides mccartyi strain CG5 and PCB-dechlorinating D. mccartyi strain CBDB1. This is the first study to retrieve potential PCB RDase genes from unenriched PCB-contaminated sediments.

Effect of biosurfactants on the aqueous solubility of PCE and TCE.

PubMed

Albino, John D; Nambi, Indumathi M

2009-12-01

The effect of biosurfactants on the solubility of tetrachloroethylene (PCE) and trichloroethylene (TCE) was studied in batch experiments pertaining to their use for solubilization and mobilization of such contaminants in surfactant enhanced aquifer remediation. Biosurfactants, rhamnolipid and surfactin used in solubility studies were synthesized in our laboratory by Pseudomonas aeruginosa (MTCC 2297) and Bacillus subtilis (MTCC 2423), respectively. The efficiency of the biosurfactants in solubilizing the chlorinated solvents was compared to that of synthetic surfactants. The Weight Solubilization Ratio (WSR) values for solubilization of PCE and TCE by biosurfactants were very high compared to the values obtained for synthetic surfactants. Surfactin proved to be a better surfactant over rhamnolipid. The WSR of surfactin on solubilization of PCE and TCE were 3.83 and 12.5, respectively, whereas the values obtained for rhamnolipid were 2.06 and 8.36. The solubility of the chlorinated solvents by biosurfactants was considerably affected by the changes in pH. The aqueous solubility of PCE and TCE increased tremendously with decrease in pH. The solubility of biosurfactants was observed to decrease with the pH, favoring partitioning of surfactants into the chlorinated solvents in significant amounts at lower pH. The excessive accumulation of biosurfactants at the interface facilitated interfacial tension reductions resulting in higher solubility of the chlorinated solvents at pH less than 7.

Reductive dechlorination of DDT to DDD by yeast

USGS Publications Warehouse

Kallman, Burton J.; Andrews, Austin K.

1963-01-01

Labeled DDD [ 1,1-dichlor-o-2,2-bis(p-chlorophenyl)-ethane] was formed from C14-labeled DDT in the presence of yeast. The formation of DDD from DDE [1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene] was not observed, indicating that a reductive dechlorination of DDT occurs.

TCE Removal From Contaminated Soil and Ground Water

EPA Pesticide Factsheets

Trichloroethylene (TCE) is a halogenated aliphatic organic compound which, due to its unique properties and solvent effects, has been widely used as an ingredient in industrial cleaning solutions and as a “universal” degreasing agent.

Effects Of Aging And Oxidation Of Palladized Iron Embedded In Activated Carbon On The Dechlorination Of 2-Chlorobiphenyl

EPA Science Inventory

Reactive activated carbon (RAC) impregnated with palladized iron has been developed to effectively treat polychlorinated biphenyls (PCBs) in the environment by coupling adsorption and dechlorination of PCBs. In this study, we addressed the dechlorination reactivity and capacity ...

Impact of estuarine gradients on reductive dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin in river sediment enrichment cultures.

PubMed

Dam, Hang T; Häggblom, Max M

2017-02-01

Polychlorinated dibenzo-p-dioxins (PCDDs) are among the most persistent organic pollutants. Although the total input of PCDDs into the environment has decreased substantially over the past four decades, their input via non-point sources is still increasing, especially in estuarine metropolitan areas. Here we report on the microbially mediated reductive dechlorination of PCDDs in anaerobic enrichment cultures established from sediments collected from five locations along the Hackensack River, NJ and investigate the impacts of sediment physicochemical characteristics on dechlorination activity. Dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD) and abundance of Dehalococcoides spp. negatively correlated with salinity and sulfate concentration in sediments used to establish the cultures. 1,2,3,4-TeCDD was dechlorinated to a lesser extent in cultures established from sediments from the tidally influenced estuarine mouth of the river. In cultures established from low salinity sediments, 1,2,3,4-TeCDD was reductively dechlorinated with the accumulation of 2-monochlorodibenzo-p-dioxin as the major product. Sulfate concentrations above 2 mM inhibited 1,2,3,4-TecDD dechlorination activity. Consecutive lateral- and peri- dechlorination took place in enrichment cultures with a minimal accumulation of 2,3-dichlorodibenzo-p-dioxin in active cultures. A Dehalococcoides spp. community was enriched and accounted for up to 64% of Chloroflexi detected in these sediment cultures. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ecology and distribution of a new biomarker linked to 1,2-dichloropropane dechlorination in subsurface environments

NASA Astrophysics Data System (ADS)

Padilla-Crespo, E.; Loeffler, F. E.

2011-12-01

Reductive dechlorination plays a major role in the transformation and detoxification of chlorinated solvents, including chlorinated ethenes. Molecular biological tools are being applied at contaminated sites in order to assess the process-specific biomarkers that impact site performance, and to monitor the progress of bioremediation approaches. The few current biomarker genes in use provide an incomplete picture of the reductively dechlorinating bacterial community; this is a limitation for implementing enhanced bioremediation and monitored natural attenuation as cleanup strategies at chlorinated solvent contaminated sites. Reductively dehalogenating organisms, particularly Dehalococcoides (Dhc) strains, possess multiple reductive dehalogenase (RDase) genes, which are promising targets to specifically monitor dehalogenation processes of interest. Dehalococcoides populations in two highly enriched cultures (RC and KS) have been implicated in the reductive dechlorination of dechlorination of 1,2-dichloropropane (1,2-D), a widespread halogenated organic pollutant, to the non-toxic propene. Using a combined approach of transcription, expression and molecular analysis a new biomarker linked to 1,2-dichloropropane has been identified in Dhc strains RC and KS providing for the first time, convincing evidence of a specific RDase implicated in 1,2-D dechlorination to propene. Further analyses imply that new biomarker is in a "mobile DNA segment", a genomic island (GI) of horizontal gene transfer origin. A valid quantitative PCR approach was designed to detect and enumerate this gene in cultures and environmental samples; this will be a useful to bioremediation practitioners to more efficiently implement reductive dechlorination as a remediation tool. The new biomarker has been identified in fresh water sediment samples from different geographical locations in Europe, North and South America. Further research aims to shed light on RDase gene dissemination and the adaptation

Porosity and pore size distribution in a sedimentary rock: Implications for the distribution of chlorinated solvents

NASA Astrophysics Data System (ADS)

Shapiro, Allen M.; Evans, Christopher E.; Hayes, Erin C.

2017-08-01

Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption. Porosity and retardation factor varied over two orders of magnitude, with the largest porosities and largest retardation factors associated with carbon-rich mudstone layers. Larger porosities were also measured in the shallow rock that has been subject to enhanced groundwater flow. Porosity also varied over more than an order of magnitude in spatially continuous mudstone layers. The analyses of the rock cores indicated that the largest pore diameters may be accessible to entry of the nonaqueous form of TCE. Although the porosity associated with the largest pore diameters is small ( 0.1%), that volume of TCE can significantly affect the total TCE that is retained in the rock matrix. The dimensions of the largest pore diameters may also be accessible to microbes responsible for reductive dechlorination; however, the small percentage of the pore space that can accommodate microbes may limit the extent of reductive dechlorination in the rock matrix.

Porosity and pore size distribution in a sedimentary rock: Implications for the distribution of chlorinated solvents

USGS Publications Warehouse

Shapiro, Allen M.; Evans, Chrsitopher E.; Hayes, Erin C.

2017-01-01

Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption. Porosity and retardation factor varied over two orders of magnitude, with the largest porosities and largest retardation factors associated with carbon-rich mudstone layers. Larger porosities were also measured in the shallow rock that has been subject to enhanced groundwater flow. Porosity also varied over more than an order of magnitude in spatially continuous mudstone layers. The analyses of the rock cores indicated that the largest pore diameters may be accessible to entry of the nonaqueous form of TCE. Although the porosity associated with the largest pore diameters is small (~ 0.1%), that volume of TCE can significantly affect the total TCE that is retained in the rock matrix. The dimensions of the largest pore diameters may also be accessible to microbes responsible for reductive dechlorination; however, the small percentage of the pore space that can accommodate microbes may limit the extent of reductive dechlorination in the rock matrix.

78 FR 17777 - Tax Counseling for the Elderly (TCE) Program Availability of Application Packages

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-22

... DEPARTMENT OF THE TREASURY Internal Revenue Service Tax Counseling for the Elderly (TCE) Program...: This document provides notice of the availability of Application Packages for the 2014 Tax Counseling... for submitting an application package to the IRS for the Tax Counseling for the Elderly (TCE) Program...

Improving the sweeping efficiency of permanganate into low permeable zones to treat TCE: experimental results and model development.

PubMed

Chokejaroenrat, Chanat; Kananizadeh, Negin; Sakulthaew, Chainarong; Comfort, Steve; Li, Yusong

2013-11-19

The residual buildup and treatment of dissolved contaminants in low permeable zones (LPZs) is a particularly challenging issue for injection-based remedial treatments. Our objective was to improve the sweeping efficiency of permanganate into LPZs to treat dissolved-phase TCE. This was accomplished by conducting transport experiments that quantified the ability of xanthan-MnO4(-) solutions to penetrate and cover (i.e., sweep) an LPZ that was surrounded by transmissive sands. By incorporating the non-Newtonian fluid xanthan with MnO4(-), penetration of MnO4(-) into the LPZ improved dramatically and sweeping efficiency reached 100% in fewer pore volumes. To quantify how xanthan improved TCE removal, we spiked the LPZ and surrounding sands with (14)C-lableled TCE and used a multistep flooding procedure that quantified the mass of (14)C-TCE oxidized and bypassed during treatment. Results showed that TCE mass removal was 1.4 times greater in experiments where xanthan was employed. Combining xanthan with MnO4(-) also reduced the mass of TCE in the LPZ that was potentially available for rebound. By coupling a multiple species reactive transport model with the Brinkman equation for non-Newtonian flow, the simulated amount of (14)C-TCE oxidized during transport matched experimental results. These observations support the use of xanthan as a means of enhancing MnO4(-) delivery into LPZs for the treatment of dissolved-phase TCE.

Consistent post-reaction vibrational energy redistribution in DSMC simulations using TCE model

NASA Astrophysics Data System (ADS)

Borges Sebastião, Israel; Alexeenko, Alina

2016-10-01

The direct simulation Monte Carlo (DSMC) method has been widely applied to study shockwaves, hypersonic reentry flows, and other nonequilibrium flow phenomena. Although there is currently active research on high-fidelity models based on ab initio data, the total collision energy (TCE) and Larsen-Borgnakke (LB) models remain the most often used chemistry and relaxation models in DSMC simulations, respectively. The conventional implementation of the discrete LB model, however, may not satisfy detailed balance when recombination and exchange reactions play an important role in the flow energy balance. This issue can become even more critical in reacting mixtures involving polyatomic molecules, such as in combustion. In this work, this important shortcoming is addressed and an empirical approach to consistently specify the post-reaction vibrational states close to thermochemical equilibrium conditions is proposed within the TCE framework. Following Bird's quantum-kinetic (QK) methodology for populating post-reaction states, the new TCE-based approach involves two main steps. The state-specific TCE reaction probabilities for a forward reaction are first pre-computed from equilibrium 0-D simulations. These probabilities are then employed to populate the post-reaction vibrational states of the corresponding reverse reaction. The new approach is illustrated by application to exchange and recombination reactions relevant to H2-O2 combustion processes.

Investigation of reductive dechlorination supported by natural organic carbon

USGS Publications Warehouse

Rectanus, H.V.; Widdowson, M.A.; Chapelle, F.H.; Kelly, C.A.; Novak, J.T.

2007-01-01

Because remediation timeframes using monitored natural attenuation may span decades or even centuries at chlorinated solvent sites, new approaches are needed to assess the long-term sustainability of reductive dechlorination in ground water systems. In this study, extraction procedures were used to investigate the mass of indigenous organic carbon in aquifer sediment, and experiments were conducted to determine if the extracted carbon could support reductive dechlorination of chloroethenes. Aquifer sediment cores were collected from a site without an anthropogenic source of organic carbon where organic carbon varied from 0.02% to 0.12%. Single extraction results showed that 1% to 28% of sediment-associated organic carbon and 2% to 36% of the soft carbon were removed depending on nature and concentration of the extracting solution (Nanopure water; 0.1%, 0.5%, and 1.0% sodium pyrophosphate; and 0.5 N sodium hydroxide). Soft carbon is defined as organic carbon oxidized with potassium persulfate and is assumed to serve as a source of biodegradable carbon within the aquifer. Biodegradability studies demonstrated that 20% to 40% of extracted organic carbon was biodegraded aerobically and anaerobically by soil microorganisms in relatively brief tests (45 d). A five-step extraction procedure consisting of 0.1% pyrophosphate and base solutions was investigated to quantify bioavailable organic carbon. Using the extracted carbon as the sole electron donor source, tetrachloroethene was transformed to cis-1,2- dichloroethene and vinyl chloride in anaerobic enrichment culture experiments. Hydrogen gas was produced at levels necessary to sustain reductive dechlorination (>1 nM). ?? 2007 National Ground Water Association.

Dechlorination of small quantities of mixed waste from a DOE site

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

Hoeffner, S.L.

1994-12-31

Sludge from tank bottoms containing PCB`s, radioactivity and hazardous constituents are present in several tanks at one of the National Laboratories. Disposal of the material can proceed if the material is removed from TSCA regulations by decreasing the concentration of the PCB`s to {le}2 ppm. ON the bench scale, this sludge was treated by the DECHLOR/KGME{sup {trademark}} chemical dechlorination process. The levels of PCB`s were reduced to below 2 ppm, allowing the material to be managed outside the TSCA regulations. RUST believes that this is the first successful chemical dechlorination of a radioactive, RCRA listed, PCB bearing waste. A pilotmore » scale unit is available to provide on-site treatment of the remaining waste. Because of the small amounts of waste, treatment costs are high on a per unit volume. As a result of these high costs and other concerns the client is investigating potential non-treatment options of delisting the waste of obtaining a waiver. In the event that this particular waste cannot be delisted or a waiver is not granted, then dechlorination of the waste to remove it from TSCA regulations remains a viable option to allow the material to be disposed.« less

A Field Trial of TCE Phytoremediation by Genetically Modified Poplars Expressing Cytochrome P450 2E1.

PubMed

Legault, Emily K; James, C Andrew; Stewart, Keith; Muiznieks, Indulis; Doty, Sharon L; Strand, Stuart E

2017-06-06

A controlled field study was performed to evaluate the effectiveness of transgenic poplars for phytoremediation. Three hydraulically contained test beds were planted with 12 transgenic poplars, 12 wild type (WT) poplars, or left unplanted, and dosed with equivalent concentrations of trichloroethylene (TCE). Removal of TCE was enhanced in the transgenic tree bed, but not to the extent of the enhanced removal observed in laboratory studies. Total chlorinated ethene removal was 87% in the CYP2E1 bed, 85% in the WT bed, and 34% in the unplanted bed in 2012. Evapotranspiration of TCE from transgenic leaves was reduced by 80% and diffusion of TCE from transgenic stems was reduced by 90% compared to WT. Cis-dichloroethene and vinyl chloride levels were reduced in the transgenic tree bed. Chloride ion accumulated in the planted beds corresponding to the TCE loss, suggesting that contaminant dehalogenation was the primary loss fate.

DISTRIBUTION OF DEHALOCCOIDES AT DOD CHLORINATED SOLVENT SITES-DO YOU NEED TO BIOAUGMENT?

EPA Science Inventory

Dehaloccoides is the only organism that has been shown to completely dechlorinate TCE, cis-DCE, and vinyl chloride to ethene or ethane (Maymo-Gatell et al., 2001; He et al., 2003a; He et al., 2003b). Dehaloccoides is a naturally occurring organism, with a world-wide distribution...

Evaluation of the effects of nanoscale zero-valent iron (nZVI) dispersants on intrinsic biodegradation of trichloroethylene (TCE).

PubMed

Chang, Y C; Huang, S C; Chen, K F

2014-01-01

In this study, the biodegradability of nanoscale zero-valent iron (nZVI) dispersants and their effects on the intrinsic biodegradation of trichloroethylene (TCE) were evaluated. Results of a microcosm study show that the biodegradability of three dispersants followed the sequence of: polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A) > polyoxyethylene (20) sorbitan monolaurate (Tween 20) > polyacrylic acid (PAA) under aerobic conditions, and PV3A > Tween 20 > PAA under anaerobic conditions. Natural biodegradation of TCE was observed under both aerobic and anaerobic conditions. No significant effects were observed on the intrinsic biodegradation of TCE under aerobic conditions with the presence of the dispersants. The addition of PAA seemed to have a slightly adverse impact on anaerobic TCE biodegradation. Higher accumulation of the byproducts of anaerobic TCE biodegradation was detected with the addition of PV3A and Tween 20. The diversity of the microbial community was enhanced under aerobic conditions with the presence of more biodegradable PV3A and Tween 20. The results of this study indicate that it is necessary to select an appropriate dispersant for nZVI to prevent a residual of the dispersant in the subsurface. Additionally, the effects of the dispersant on TCE biodegradation and the accumulation of TCE biodegrading byproducts should also be considered.

DDT, DDD, AND DDE DECHLORINATION BY ZERO-VALENT IRON

EPA Science Inventory

Traditionally, destruction of DDT [1,1,1-trichIoro-2,2-bis(p-chlorophenyl)ethane] for environmental remediation required high-energy processes such as incineration. Here, the capability of powdered zero-valent iron to dechlorinate DDT and related compounds at room tempera...

Electron donor preference of a reductive dechlorinating consortium

USGS Publications Warehouse

Lorah, M.M.; Majcher, E.; Jones, E.; Driedger, G.; Dworatzek, S.; Graves, D.

2005-01-01

A wetland sediment-derived microbial consortium was developed by the USGS and propagated in vitro to large quantities by SiREM Laboratory for use in bioaugmentation applications. The consortium had the capacity to completely dechlorinate 1,1,2,2-tetrachloroethene, tetrachloroethylene, trichloroethylene, 1,1,2-trichloroethane, cis- and trans-1,2-dichoroethylene, 1.1-dichloroethylene, 1,2-dichloroethane, vinyl chloride, carbon tetrachloride and chloroform. A suite of electron donors with characteristics useful for bioaugmentation applications was tested. The electron donors included lactate (the donor used during WBC-2 development), ethanol, chitin (Chitorem???), hydrogen releasing compound (HRC???), emulsified vegetable oil (Newman Zone???), and hydrogen gas. Ethanol, lactate, and chitin were particularly effective with respect to stimulating, supporting, and sustaining reductive dechlorination of the broad suite of chemicals that WBC-2 biodegraded. Chitorem??? was the most effective "slow release" electron donor tested. This is an abstract of a paper presented at the Proceedings of the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).

Dechlorination of trichloroethylene formed from 1,1,2,2-tetrachloroethane by dehydrochlorination in Portland cement slurry including Fe(II).

PubMed

Jung, Bahngmi; Batchelor, Bill

2008-03-01

Transformation of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) by Fe(II) in 10% cement slurries was characterized using a batch reactor system. 1,1,2,2-TeCA was completely converted to trichloroethylene (TCE) within 1h in all experiments, even in controls with cement that did not include Fe(II). Therefore, complete degradation of 1,1,2,2-TeCA depends on the behavior of TCE. The half-life of TCE was observed to be 15d when concentrations of Fe(II) and 1,1,2,2-TeCA were 98mM and 0.245mM, respectively. The kinetics of TCE removal was observed to be dependent on Fe(II) dose, pH and initial substrate concentration. Pseudo-first-order rate constants linearly increased with Fe(II) dose up to 198mM when initial target concentration was 0.245mM. Pseudo-first-order kinetics generally described the degradation reactions of TCE at a specific initial concentration, but a modified Langmuir-Hinshelwood model was necessary to describe the degradation kinetics of TCE over a wide range of initial concentrations. A surface reaction of TCE on active solids, which were formed from Fe(II) and products of cement hydration appears to control observed TCE degradation kinetics.

Mammalian cytochrome CYP2E1 triggered differential gene regulation in response to trichloroethylene (TCE) in a transgenic poplar.

PubMed

Kang, Jun Won; Wilkerson, Hui-Wen; Farin, Federico M; Bammler, Theo K; Beyer, Richard P; Strand, Stuart E; Doty, Sharon L

2010-08-01

Trichloroethylene (TCE) is an important environmental contaminant of soil, groundwater, and air. Studies of the metabolism of TCE by poplar trees suggest that cytochrome P450 enzymes are involved. Using poplar genome microarrays, we report a number of putative genes that are differentially expressed in response to TCE. In a previous study, transgenic hybrid poplar plants expressing mammalian cytochrome P450 2E1 (CYP2E1) had increased metabolism of TCE. In the vector control plants for this construct, 24 h following TCE exposure, 517 genes were upregulated and 650 genes were downregulated over 2-fold when compared with the non-exposed vector control plants. However, in the transgenic CYP2E1 plant, line 78, 1,601 genes were upregulated and 1,705 genes were downregulated over 2-fold when compared with the non-exposed transgenic CYP2E1 plant. It appeared that the CYP2E1 transgenic hybrid poplar plants overexpressing mammalian CYP2E1 showed a larger number of differentially expressed transcripts, suggesting a metabolic pathway for TCE to metabolites had been initiated by activity of CYP2E1 on TCE. These results suggest that either the over-expression of the CYP2E1 gene or the abundance of TCE metabolites from CYP450 2E1 activity triggered a strong genetic response to TCE. Particularly, cytochrome p450s, glutathione S-transferases, glucosyltransferases, and ABC transporters in the CYP2E1 transgenic hybrid poplar plants were highly expressed compared with in vector controls.

Anaerobic bioremediation of groundwater containing a mixture of 1,1,2,2-tetrachloroethane and chloroethenes.

PubMed

Aulenta, Federico; Potalivo, Monica; Majone, Mauro; Papini, Marco Petrangeli; Tandoi, Valter

2006-06-01

This study investigated the biotransformation pathways of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) in the presence of chloroethenes (i.e. tetrachloroethene, PCE; trichloroethene, TCE) in anaerobic microcosms constructed with subsurface soil and groundwater from a contaminated site. When amended with yeast extract, lactate, butyrate, or H2 and acetate, 1,1,2,2-TeCA was initially dechlorinated via both hydrogenolysis to 1,1,2-trichloroethane (1,1,2-TCA) (major pathway) and dichloroelimination to dichloroethenes (DCEs) (minor pathway), with both reactions occurring under sulfidogenic conditions. In the presence of only H2, the hydrogenolysis of 1,1,2,2-TeCA to 1,1,2-TCA apparently required the presence of acetate to occur. Once formed, 1,1,2-TCA was degraded predominantly via dichloroelimination to vinyl chloride (VC). Ultimately, chloroethanes were converted to chloroethenes (mainly VC and DCEs) which persisted in the microcosms for very long periods along with PCE and TCE originally present in the groundwater. Hydrogenolysis of chloroethenes occurred only after highly reducing methanogenic conditions were established. However, substantial conversion to ethene (ETH) was observed only in microcosms amended with yeast extract (200 mg/l), suggesting that groundwater lacked some nutritional factors which were likely provided to dechlorinating microorganisms by this complex organic substrate. Bioaugmentation with an H2-utilizing PCE-dechlorinating Dehalococcoides spp. -containing culture resulted in the conversion of 1,1,2,2-TeCA, PCE and TCE to ETH and VC. No chloroethanes accumulated during degradation suggesting that 1,1,2,2-TeCA was degraded through initial dichloroelimination into DCEs and then typical hydrogenolysis into ETH and VC.

System for In-Situ Detection of Plant Exposure to Trichloroethylene (TCE)

NASA Technical Reports Server (NTRS)

Newman, Lee A. (Inventor); Lewis, Mark D. (Inventor); Anderson, Daniel J. (Inventor); Keith, Amy G. (Inventor)

2013-01-01

A system detects a plant's exposure to trichloroethylene (TCE) through plant leaf imaging. White light impinging upon a plant's leaf interacts therewith to produce interacted light. A detector is positioned to detect at least one spectral band of the interacted light. A processor coupled to the detector performs comparisons between photonic energy of the interacted light at the one or more spectral bands thereof and reference data defining spectral responses indicative of leaf exposure to TCE. An output device coupled to the processor provides indications of the comparisons.

Transformation of mackinawite to greigite by trichloroethylene and tetrachloroethylene.

PubMed

Lan, Ying; Elwood Madden, Andrew S; Butler, Elizabeth C

2016-10-12

Trichloroethylene (TCE) and tetrachloroethylene (PCE) are common ground water contaminants susceptible to reductive dechlorination by FeS (mackinawite) in anaerobic environments. The objective of this study was to characterize the mineral-associated products that form when mackinawite reacts with TCE and PCE. The dissolved products of the reaction included Cl - and Fe 2+ , and trace amounts of cis 1,2-dichloroethylene (for TCE) and TCE (for PCE). Selected area electron diffraction (SAED) analysis identified greigite as a mackinawite oxidation product formed after reaction between TCE or PCE and FeS over seven weeks. Release of Fe 2+ is consistent with the solid state transformation of mackinawite to greigite, resulting in depletion of the solid with Fe. X-ray photoelectron spectroscopy of the sulfur 2p peak showed a shift to a higher binding energy after FeS reacted with TCE or PCE, also observed in other studies of mackinawite oxidation to greigite. The results may help efforts to maintain the reactivity of FeS generated to remediate chlorinated aliphatic contaminants in ground water.

Microbial community analysis of switchgrass planted and unplanted soil microcosms displaying PCB dechlorination

PubMed Central

Liang, Yi; Meggo, Richard; Hu, Dingfei; Schnoor, Jerald L.; Mattes, Timothy E.

2015-01-01

Polychlorinated biphenyls (PCBs) pose potential risks to human and environmental health because they are carcinogenic, persistent and bioaccumulative. In this study we investigated bacterial communities in soil microcosms spiked with PCB 52, 77 and 153. Switchgrass (Panicum virgatum) was employed to improve overall PCB removal and redox cycling (i.e. sequential periods of flooding followed by periods of no flooding) was performed in an effort to promote PCB dechlorination. Lesser chlorinated PCB transformation products were detected in all microcosms, indicating the occurrence of PCB dechlorination. Terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis showed that PCB spiking, switchgrass planting and redox cycling affected the microbial community structure. Putative organohalide-respiring Chloroflexi populations, which were not found in unflooded microcosms, were enriched after two weeks of flooding in the redox-cycled microcosms. Sequences classified as Geobacter sp. were detected in all microcosms, and were most abundant in the switchgrass-planted microcosm spiked with PCB congeners. The presence of possible organohalide-respiring bacteria in these soil microcosms suggests they play a role in PCB dechlorination therein. PMID:25820643

Microbial community analysis of switchgrass planted and unplanted soil microcosms displaying PCB dechlorination.

PubMed

Liang, Yi; Meggo, Richard; Hu, Dingfei; Schnoor, Jerald L; Mattes, Timothy E

2015-08-01

Polychlorinated biphenyls (PCBs) pose potential risks to human and environmental health because they are carcinogenic, persistent, and bioaccumulative. In this study, we investigated bacterial communities in soil microcosms spiked with PCB 52, 77, and 153. Switchgrass (Panicum virgatum) was employed to improve overall PCB removal, and redox cycling (i.e., sequential periods of flooding followed by periods of no flooding) was performed in an effort to promote PCB dechlorination. Lesser chlorinated PCB transformation products were detected in all microcosms, indicating the occurrence of PCB dechlorination. Terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis showed that PCB spiking, switchgrass planting, and redox cycling affected the microbial community structure. Putative organohalide-respiring Chloroflexi populations, which were not found in unflooded microcosms, were enriched after 2 weeks of flooding in the redox-cycled microcosms. Sequences classified as Geobacter sp. were detected in all microcosms and were most abundant in the switchgrass-planted microcosm spiked with PCB congeners. The presence of possible organohalide-respiring bacteria in these soil microcosms suggests that they play a role in PCB dechlorination therein.

PILOT SCALE REACTOR FOR ELECTROCHEMICAL DECHLORINATION OF MODEL CHLORINATED CONTAMINANTS

EPA Science Inventory

Electrochemical degradation (ECD) is a promising technology for in-situ remediation of diversely contaminated submarine matrices, by the application of low level DC electric fields. This study, prompted by successful bench-scale electrochemical dechlorination of Trichloroe...

RELATIONSHIP BETWEEN DEHALOCOCCOIDES DNA AND DECHLORINATION RATES AT FIELD SITES

EPA Science Inventory

Chlorinated ethenes are common contaminants in groundwater. To date, Dehalococcoides species are the only known organisms capable of completely dechlorinating all chlorinated ethenes to non-toxic ethene. Studies in the laboratory have shown a good correlation between Dehalococco...

Impact of FeS Mineralogy on TCE Degradation

EPA Science Inventory

Iron- and sulfate-reducing conditions are often encountered in permeable reactive barrier (PRB) systems that are constructed to remove TCE from groundwater, which usually leads to the accumulation of FeS mineral phases in the matrix of the PRB. Poorly crystalline mackinawite (Fe...

Evaluation of biodegradable plastics as solid hydrogen donors for the reductive dechlorination of fthalide by Dehalobacter species.

PubMed

Yoshida, Naoko; Ye, Lizhen; Liu, Fengmao; Li, Zhiling; Katayama, Arata

2013-02-01

Biodegradable plastics (BPs) were evaluated for their applicability as sustainable and solid H(2) donors for microbial reductive dechlorination of 4,5,6,7-tetrachlorophthalide (fthalide). After a screening test of several BPs, the starch-based plastic (SP) that produced the highest levels of H(2) was selected for its use as the sole H(2) donor in this reaction. Fthalide dechlorination was successfully accomplished by combining an H(2)-producing SP culture and a KFL culture containing Dehalobacter species, supplemented with 0.13% and 0.5% SP, respectively. The efficiency of H(2) use in dechlorination was evaluated in a combined culture containing the KFL culture and strain Clostridium sp. Ma13, a new isolate that produces H(2) from SP. Results obtained with this culture indicated increased H(2)-fraction for fthalide dechlorination much more in this culture than in compared with a KFL culture supplemented with 20mM lactate, which are 0.75 H(2)·glucose(-1) and 0.015 H(2)·lactate(-1) in mol ratio, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

75 FR 25319 - Tax Counseling for the Elderly (TCE) Program Availability of Application Packages; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-07

... DEPARTMENT OF THE TREASURY Internal Revenue Service Tax Counseling for the Elderly (TCE) Program...: Correction to a notice. SUMMARY: This document contains a correction to a notice of the Tax Counseling for... application packages for the 2011 Tax Counseling for the Elderly (TCE) Program. FOR FURTHER INFORMATION...

The influence of different geotechnically relevant amendments on the reductive degradation of TCE by nZVI

NASA Astrophysics Data System (ADS)

Freitag, Peter; Schöftner, Philipp; Waldner, Georg; Reichenauer, Thomas G.; Nickel, Claudia; Spitz, Marcus; Dietzel, Martin

2014-05-01

Trichloroethylene (TCE) was widely used as a cleaning and degreasing agent. Companies needing these agents were often situated in or close to built up areas, so spillage led to contaminated sites which now can only be remediated using in situ techniques. The situation is compounded by the fact that TCE tends to seep through ground water bodies forming pools at the bottom of the aquifer. When reacting with TCE, nanoscale zero valent iron (nZVI) is known to reduce it into non-toxic substances. The difficulty is to bring it in contact with the pollutant. Attempts using passive insertion into the groundwater via wells yielded mixed results. Reasons for this are that ZVI tends to coagulate, to sediment and to adsorb on the matrix of the aquifer. Also, in inhomogeneous aquifers a passive application of nZVI can be difficult and might not bring the desired results, due to existence of preferential flow paths. A possible solution to this problem is the physical in situ mixing of ZVI into the contaminant source. This can, in principle, be done by adapting jet grouting - a method that uses a high pressure slurry jet, consisting of water and geotechnical additives ("binders"), to mix and compact zones ("columns") in soil. These columns are commonly used to solve foundation problems but can also be used to solve the problem of delivering nZVI to TCE source zones. This paper examines the influence binders have on the degradation reaction between TCE and nZVI. The necessity of these binders is explained by the fact that the subsoil structure is rearranged during the jetting process leading to subsidence on the surface. These subsidences could result in damage to neighbouring structures. A series of batch experiments was conducted in this study. Contaminated groundwater was brought into contact with samples of slurries commonly used in geotechnical applications. We tested the effects of concresole, bentonite, zeolithe, fly ash, slag sand and cement on the kinetics of TCE

Accelerated anaerobic dechlorination of DDT in slurry with Hydragric Acrisols using citric acid and anthraquinone-2,6-disulfonate (AQDS).

PubMed

Liu, Cuiying; Xu, Xianghua; Fan, Jianling

2015-12-01

The application of electron donor and electron shuttle substances has a vital influence on electron transfer, thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis(p-chlorophenyl)ethane (DDT) in anaerobic reaction systems. To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate (AQDS) in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide, a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of (1) control, (2) citric acid, (3) AQDS, and (4) citric acid+AQDS. Results showed that DDT residues decreased by 78.93%-92.11% of the initial quantities after 20days of incubation, and 1,1-dichloro-2,2-bis(4-chlorophenyl)-ethane (DDD) was the dominant metabolite. The application of citric acid accelerated DDT dechlorination slightly in the first 8days, while the methanogenesis rate increased quickly, and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased. The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe(III) oxides to generate Fe(II), which was an efficient electron donor, thus enhancing the reductive dechlorination rate of DDT. The addition of citric acid+AQDS was most efficient in stimulating DDT dechlorination, but no significant interaction between citric acid and AQDS on DDT dechlorination was observed. The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites. Copyright © 2015. Published by Elsevier B.V.

Aerobic Degradation of Trichloroethylene by Co-Metabolism Using Phenol and Gasoline as Growth Substrates

PubMed Central

Li, Yan; Li, Bing; Wang, Cui-Ping; Fan, Jun-Zhao; Sun, Hong-Wen

2014-01-01

Trichloroethylene (TCE) is a common groundwater contaminant of toxic and carcinogenic concern. Aerobic co-metabolic processes are the predominant pathways for TCE complete degradation. In this study, Pseudomonas fluorescens was studied as the active microorganism to degrade TCE under aerobic condition by co-metabolic degradation using phenol and gasoline as growth substrates. Operating conditions influencing TCE degradation efficiency were optimized. TCE co-metabolic degradation rate reached the maximum of 80% under the optimized conditions of degradation time of 3 days, initial OD600 of microorganism culture of 0.14 (1.26 × 107 cell/mL), initial phenol concentration of 100 mg/L, initial TCE concentration of 0.1 mg/L, pH of 6.0, and salinity of 0.1%. The modified transformation capacity and transformation yield were 20 μg (TCE)/mg (biomass) and 5.1 μg (TCE)/mg (phenol), respectively. Addition of nutrient broth promoted TCE degradation with phenol as growth substrate. It was revealed that catechol 1,2-dioxygenase played an important role in TCE co-metabolism. The dechlorination of TCE was complete, and less chlorinated products were not detected at the end of the experiment. TCE could also be co-metabolized in the presence of gasoline; however, the degradation rate was not high (28%). When phenol was introduced into the system of TCE and gasoline, TCE and gasoline could be removed at substantial rates (up to 59% and 69%, respectively). This study provides a promising approach for the removal of combined pollution of TCE and gasoline. PMID:24857922

Aerobic degradation of trichloroethylene by co-metabolism using phenol and gasoline as growth substrates.

PubMed

Li, Yan; Li, Bing; Wang, Cui-Ping; Fan, Jun-Zhao; Sun, Hong-Wen

2014-05-22

Trichloroethylene (TCE) is a common groundwater contaminant of toxic and carcinogenic concern. Aerobic co-metabolic processes are the predominant pathways for TCE complete degradation. In this study, Pseudomonas fluorescens was studied as the active microorganism to degrade TCE under aerobic condition by co-metabolic degradation using phenol and gasoline as growth substrates. Operating conditions influencing TCE degradation efficiency were optimized. TCE co-metabolic degradation rate reached the maximum of 80% under the optimized conditions of degradation time of 3 days, initial OD600 of microorganism culture of 0.14 (1.26×10⁷ cell/mL), initial phenol concentration of 100 mg/L, initial TCE concentration of 0.1 mg/L, pH of 6.0, and salinity of 0.1%. The modified transformation capacity and transformation yield were 20 μg (TCE)/mg (biomass) and 5.1 μg (TCE)/mg (phenol), respectively. Addition of nutrient broth promoted TCE degradation with phenol as growth substrate. It was revealed that catechol 1,2-dioxygenase played an important role in TCE co-metabolism. The dechlorination of TCE was complete, and less chlorinated products were not detected at the end of the experiment. TCE could also be co-metabolized in the presence of gasoline; however, the degradation rate was not high (28%). When phenol was introduced into the system of TCE and gasoline, TCE and gasoline could be removed at substantial rates (up to 59% and 69%, respectively). This study provides a promising approach for the removal of combined pollution of TCE and gasoline.

GREEN AND SUSTAINABLE REMEDIATION BEST MANAGEMENT PRACTICES

DTIC Science & Technology

2016-09-07

adoption. The technologies covered include air sparging, biosparging, soil vapor extraction (SVE), enhanced reductive dechlorination (ERD), in situ...RPM Remedial Project Manager SCR selective catalytic reduction SEE steam enhanced extraction SVE soil vapor extraction TCE trichloroethene...further promote their adoption. The technologies covered include air sparging, biosparging, soil vapor extraction (SVE), enhanced reductive

An Approach Using Gas Monitoring to Find the Residual TCE Location in the Unsaturated Zone of Woosan Industrial Complex (WIC), Korea

NASA Astrophysics Data System (ADS)

Koh, Y.; Lee, S.; Yang, J.; Lee, K.

2012-12-01

An area accommodating various industrial facilities has fairly high probability of groundwater contamination with multiple chlorinated solvents such as trichloroethene (TCE), carbon tetrachloride (CT), and chloroform (CF). Source tracing of chlorinated solvents in the unsaturated zone is an essential procedure for the management and remediation of contaminated area. From the previous study on seasonal variations in hydrological stresses and spatial variations in geologic conditions on a TCE plume, the existence of residual DNAPLs at or above the water table has proved. Since TCE is one of the frequently detected VOCs (Volatile Organic Compounds) in groundwater, residual TCE can be detected by gas monitoring. Therefore, monitoring of temporal and spatial variations in the gas phase TCE contaminant at an industrial complex in Wonju, Korea, were used to find the residual TCE locations. As pilot tests, TCE gas samples collected in the unsaturated zone at 4 different wells were analyzed using SPME (Solid Phase MicroExtraction) fiber and Gas Chromatography (GC). The results indicated that detecting TCE in gas phase was successful from these wells and TCE analysis on gas samples, collected from the unsaturated zone, will be useful for source area characterization. However, some values were too high to doubt the accuracy of the current method, which needs a preliminary lab test with known concentrations. The modified experiment setups using packer at different depths are in process to find residual TCE locations in the unsaturated zone. Meanwhile, several PVD (polyethylene-membrane Passive Vapor Diffusion) samplers were placed under water table to detect VOCs by equilibrium between air in the vial and VOCs in pore water.

Enhanced degradation of trichloroethene by calcium peroxide activated with Fe(III) in the presence of citric acid

PubMed Central

ZHANG, Xiang; GU, Xiaogang; LU, Shuguang; MIAO, Zhouwei; XU, Minhui; FU, Xiaori; DANISH, Muhammad; Brusseau, Mark L.; QIU, Zhaofu; SUI, Qian

2017-01-01

Trichloroethene (TCE) degradation by Fe(III)-activated calcium peroxide (CP) in the presence of citric acid (CA) in aqueous solution was investigated. The results demonstrated that the presence of CA enhanced TCE degradation significantly by increasing the concentration of soluble Fe(III) and promoting H2O2 generation. The generation of HO• and O2−• in both the CP/Fe(III) and CP/Fe(III)/CA systems was confirmed with chemical probes. The results of radical scavenging tests showed that TCE degradation was due predominantly o direct oxidation by HO•, while O2−• strengthened the generation of HO• by promoting Fe(III) transformation in the CP/Fe(III)/CA system. Acidic pH conditions were favorable for TCE degradation, and the TCE degradation rate decreased with increasing pH. The presence of Cl−, HCO3−, and humic acid (HA) inhibited TCE degradation to different extents for the CP/Fe(III)/CA system. Analysis of Cl− production suggested that TCE degradation in the CP/Fe(III)/CA system occurred through a dechlorination process. In summary, this study provided detailed information for the application of CA-enhanced Fe(III)-activated calcium peroxide for treating TCE contaminated groundwater. PMID:28959499

Assessment of trichloroethylene (TCE) exposure in murine strains genetically-prone and non-prone to develop autoimmune disease.

PubMed

Keil, Deborah E; Peden-Adams, Margie M; Wallace, Stacy; Ruiz, Phillip; Gilkeson, Gary S

2009-04-01

There is increasing laboratory and epidemiologic evidence relating exposure to trichloroethylene (TCE) with autoimmune disease including scleroderma and lupus. New Zealand Black/New Zealand White (NZBWF1) and B6C3F1 mice were exposed to TCE (0, 1, 400 or 14,000 ppb) via drinking water for 27 or 30 weeks, respectively. NZBWF1 mice spontaneously develop autoimmune disease while B6C3F1 mice, a standard strain used in immunotoxicology testing, are not genetically prone to develop autoimmune disease. During the TCE exposure period, serum levels of total IgG, and autoantibodies (anti-ssDNA, -dsDNA, and -glomerular antigen [GA]) were monitored. At the termination of the study, renal pathology, natural killer (NK) cell activity, total IgG levels, autoantibody production, T-cell activation, and lymphocytic proliferative responses were evaluated. TCE did not alter NK cell activity, or T- and B-cell proliferation in either strain. Numbers of activated T-cells (CD4+/CD44+) were increased in the B6C3F1 mice but not in the NZBWF1 mice. Renal pathology, as indicated by renal score, was significantly increased in the B6C3F1, but not in the NZBWF1 mice. Serum levels of autoantibodies to dsDNA and ssDNA were increased at more time points in B6C3F1, as compared to the NZBWF1 mice. Anti-GA autoantibodies were increased by TCE treatment in early stages of the study in NZBWF1 mice, but by 23 weeks of age, control levels were comparable to those of TCE-exposed animals. Serum levels anti-GA autoantibodies in B6C3F1 were not affected by TCE exposure. Overall, these data suggest that TCE did not contribute to the progression of autoimmune disease in autoimmune-prone mice during the period of 11-36 weeks of age, but rather lead to increased expression of markers associated with autoimmune disease in a non-genetically prone mouse strain.

Enhancement of TCE removal by a static magnetic field in a fungal biotrickling filter.

PubMed

Quan, Yue; Wu, Hao; Guo, Chunyu; Han, Yu; Yin, Chengri

2018-07-01

A fungal biotrickling filter (BTF) was employed to treat trichloroethylene (TCE) gas under different magnetic field intensities (MFIs). When the TCE inlet concentrations were approximately 370, 500-900, and 1000 mg/m 3 , the removal performances followed the order: MFI 20.0 mT > MFI 60.0 mT > MFI 80.0 mT > MFI 0 mT. In particular, at a TCE inlet concentration of 1000 mg/m 3 , MFI 20.0 mT was significantly better than MFI 0 mT performance. The corresponding removal efficiencies and maximum elimination capacities were 52.9%, 4854.1 mg/m 3  h and 39.4%, 3594.8 mg/m 3  h, respectively. BTF was shut down completely for 7 days and rapidly recovered in 6-10 days. High-throughput sequencing indicated that MF significantly affected the fungal community and significantly improved the relative abundance of the phylum Ascomycota, achieving the highest abundance of Ascomycota at MFI 20.0. These results indicated that a lower MFI can efficiently improve TCE removal performance in a fungal BTF. Copyright © 2018 Elsevier Ltd. All rights reserved.

Feasibility study of Tethered Capsule Endomicroscopy (TCE) deployment in the small intestine (Conference Presentation)

NASA Astrophysics Data System (ADS)

Otuya, David O.; Verma, Yogesh; Dong, Jing; Gora, Michalina J.; Tearney, Guillermo J.

2017-02-01

Environmental enteric dysfunction (EED) is a poorly understood disease of the small intestine that causes nutrient malabsorption in children, predominantly from low and middle income countries. The clinical importance of EED is neurological and growth stunting that remains as the child grows into adulthood. Tethered capsule endomicroscopy (TCE) has the potential to improve the understanding of EED and could be used to determine the effectiveness of EED interventions. TCE in the adult esophagus and the duodenum has been demonstrated for Barrett`s esophagus and celiac disease diagnosis, respectively. While adult subjects can independently swallow these capsules, it is likely that infants will not, and, as a result, new strategies for introducing these devices in young children aged 0.5-2 years need to be investigated. Our first approach will be to introduce the TCE devices in infants under the aid of endoscopic guidance. To determine the most effective method, we have tested endoscopic approaches for introducing TCE devices into the small intestine of living swine. These methods will be compared and contrasted to discuss the most effective means for endoscopic tethered capsule introduction into the small intestine.

TCE TRANSPORT AND DEGRADATION IN SOIL USING ELECTROOSMOSIS

EPA Science Inventory

Laboratory experiments were used to characterize the transport and chemical transformation of TCE in undisturbed soil cores. Electroosmotic fluid flow was vertically downwards from anode to cathode. A voltage of 1.4 V/cm was applied to the soil for 4 weeks. More than 95% of the T...

Discovery of a trans-Dichloroethene-Respiring Dehalogenimonas Species in the 1,1,2,2-Tetrachloroethane-Dechlorinating WBC-2 Consortium

PubMed Central

Manchester, Marie J.; Hug, Laura A.; Zarek, Matt; Zila, Anna

2012-01-01

The WBC-2 consortium is an organohalide-respiring anaerobic microbial enrichment culture capable of dechlorinating 1,1,2,2-tetrachloroethane (TeCA) to ethene. In the WBC-2 culture, TeCA is first transformed to trans-dichloroethene (tDCE) by dichloroelimination; tDCE is subsequently transformed to vinyl chloride (VC) and then to ethene by hydrogenolysis. Analysis of 16S rRNA gene clone libraries from culture DNA revealed sequences from three putative dechlorinating organisms belonging to Dehalococcoides, Dehalobacter, and Dehalogenimonas genera. Quantitative PCR primers were designed for each of these sequences, and their abundance was quantified in enrichment cultures over time. These data revealed that complete dechlorination of TeCA to ethene involves all three organisms. Dehalobacter spp. grew during the dihaloelimination of TeCA to tDCE, while Dehalococcoides and Dehalogenimonas spp. grew during hydrogenolysis of tDCE to ethene. This is the first time a genus other than Dehalococcoides has been implicated in dechlorination of tDCE to VC. PMID:22635995

A Planet Hunters Search of the Kepler TCE Inventory

NASA Astrophysics Data System (ADS)

Schwamb, Meg; Lintott, Chris; Fischer, Debra; Smith, Arfon; Boyajian, Tabetha; Brewer, John; Giguere, Matt; Lynn, Stuart; Schawinski, Kevin; Simpson, Rob; Wang, Ji

2013-07-01

NASA's Kepler spacecraft has spent the past 4 years monitoring ~160,000 stars for the signatures of transiting exoplanets. Planet Hunters (http://www.planethunters.org), part of the Zooniverse (http://www.zooniverse.org) collection of citizen science projects, uses the power of human pattern recognition via the World Wide Web to identify transits in the Kepler public data. We have demonstrated the success of a citizen science approach with the project's discoveries including PH1 b, a transiting circumbinary planet in a four star system., and over 20 previously unknown planet candidates. The Kepler team has released the list of 18,406 potential transit signals or threshold-crossing events (TCEs) identified in Quarters 1-12 (~1000 days) by their automated Transit Planet Search (TPS) algorithm. The majority of these detections found by TPS are triggered by transient events and are not valid planet candidates. To identify planetary candidates from the detected TCEs, a human review of the validation reports, generated by the Kepler pipeline for each TCE, is performed by several Kepler team members. We have undertaken an independent crowd-sourced effort to perform a systematic search of the Kepler Q1-12 TCE list. With the Internet we can obtain multiple assessments of each TCE's data validation report. Planet Hunters volunteers evaluate whether a transit is visible in the Kepler light curve folded on the expected period identified by TPS. We present the first results of this analysis.

IRIS Toxicological Review of Trichloroethylene (TCE) (External Review Draft)

EPA Science Inventory

EPA is conducting a peer review and public comment of the scientific basis supporting the human health hazard and dose-response assessment of Trichloroethylene (TCE) that when finalized will appear on the Integrated Risk Information System (IRIS) database.

Complementing approaches to demonstrate chlorinated solvent biodegradation in a complex pollution plume: Mass balance, PCR and compound-specific stable isotope analysis

NASA Astrophysics Data System (ADS)

Courbet, Christelle; Rivière, Agnès; Jeannottat, Simon; Rinaldi, Sandro; Hunkeler, Daniel; Bendjoudi, Hocine; de Marsily, Ghislain

2011-11-01

This work describes the use of different complementing methods (mass balance, polymerase chain reaction assays and compound-specific stable isotope analysis) to demonstrate the existence and effectiveness of biodegradation of chlorinated solvents in an alluvial aquifer. The solvent-contaminated site is an old chemical factory located in an alluvial plain in France. As most of the chlorinated contaminants currently found in the groundwater at this site were produced by local industries at various times in the past, it is not enough to analyze chlorinated solvent concentrations along a flow path to convincingly demonstrate biodegradation. Moreover, only a few data were initially available to characterize the geochemical conditions at this site, which were apparently complex at the source zone due to (i) the presence of a steady oxygen supply to the groundwater by irrigation canal losses and river infiltration and (ii) an alkaline pH higher than 10 due to former underground lime disposal. A demonstration of the existence of biodegradation processes was however required by the regulatory authority within a timeframe that did not allow a full geochemical characterization of such a complex site. Thus a combination of different fast methods was used to obtain a proof of the biodegradation occurrence. First, a mass balance analysis was performed which revealed the existence of a strong natural attenuation process (biodegradation, volatilization or dilution), despite the huge uncertainty on these calculations. Second, a good agreement was found between carbon isotopic measurements and PCR assays (based on 16S RNA gene sequences and functional genes), which clearly indicated reductive dechlorination of different hydrocarbons (Tetrachloroethene—PCE-, Trichloroethene—TCE-, 1,2- cisDichloroethene— cis-1,2-DCE-, 1,2- transDichloroethene— trans-1,2-DCE-, 1,1-Dichloroethene—1,1-DCE-, and Vinyl Chloride—VC) to ethene. According to these carbon isotope measurements

USE OF CARBON STABLE ISOTOPE FOR THE DECHLORINATION OF TRICHLOROETHYLENE ON GRANULAR-GRAPHITE PACKED ELECTRODES (PRESENTATION)

EPA Science Inventory

Trichloroethylene (TCE) is widely used as a solvent in metal processing and electronic manufacturing industries, but waste and spilled TCE often results in blocks of non-aqueous liquid in vadose and saturated zones which become continuous contamination sources for groundwater. El...

Evaluation of areas of contribution and water quality at receptors related to TCE plumes in a valley fill aquifer system

NASA Astrophysics Data System (ADS)

Lefebvre, R.; Ouellon, T.; Blais, V.; Ballard, J.; Brunet, P.

2009-05-01

The Val-Belair sector is located within Quebec City, about 20 km from downtown. Potential source zones and TCE plumes in groundwater are found at the western limit of the sector. At the center of the sector, four municipal water supply wells pump groundwater from an aquifer in surficial sediments where dissolved TCE is found. Private residential wells are also found in the sector. The Nelson River and its tributaries drain the sector and flows from west to east. New characterization results and available data were used to develop a numerical model of groundwater flow and mass transport to 1) define geological and hydrogeological contexts, 2) delineate the distribution of TCE and identify its migration paths and 3) evaluate the effect of TCE on the water quality of receptors (Nelson River, municipal and residential wells). In the sector, 30 to 40 m of sediments filling a buried valley form two aquifers separated by an aquitard: an unconfined deltaic aquifer at surface, an underlying silty prodeltaic aquitard and a semi-confined aquifer of deltaic sands and diamictons. Groundwater exchanges between the aquifers are generally downward through the aquitard, but near the Nelson River there is upward flow. Monitoring has led to sparse TCE detections in the Nelson River, regular detections at a mean value of 0.62 μg/L at one municipal well, occasional detections at another well and no detection at the other two wells. No TCE was detected in private wells, which are located outside the migration paths of TCE plumes. The context and numerical modeling with particle tracking and mass transport show the relationships between the two source zones, three TCE plumes and three receptors. Municipal wells pump in the semi-confined aquifer at a level appearing sustainable, but use most of the recharge in the sub-watershed. Areas of contribution to the wells thus cover almost all the study area with a complex pattern. These wells compete with the effect of the Nelson River to drain

Air purification from TCE and PCE contamination in a hybrid bioreactors and biofilter integrated system.

PubMed

Tabernacka, Agnieszka; Zborowska, Ewa; Lebkowska, Maria; Borawski, Maciej

2014-01-15

A two-stage waste air treatment system, consisting of hybrid bioreactors (modified bioscrubbers) and a biofilter, was used to treat waste air containing chlorinated ethenes - trichloroethylene (TCE) and tetrachloroethylene (PCE). The bioreactor was operated with loadings in the range 0.46-5.50gm(-3)h(-1) for TCE and 2.16-9.02gm(-3)h(-1) for PCE. The biofilter loadings were in the range 0.1-0.97gm(-3)h(-1) for TCE and 0.2-2.12gm(-3)h(-1) for PCE. Under low pollutant loadings, the efficiency of TCE elimination was 23-25% in the bioreactor and 54-70% in the biofilter. The efficiency of PCE elimination was 44-60% in the bioreactor and 50-75% in the biofilter. The best results for the bioreactor were observed one week after the pollutant loading was increased. However, the process did not stabilize. In the next seven days contaminant removal efficiency, enzymatic activity and biomass content were all diminished. Copyright © 2013 Elsevier B.V. All rights reserved.

Exposure of Daphnia magna to trichloroethylene (TCE) and vinyl chloride (VC): evaluation of gene transcription, cellular activity, and life-history parameters.

PubMed

Houde, Magali; Douville, Mélanie; Gagnon, Pierre; Sproull, Jim; Cloutier, François

2015-06-01

Trichloroethylene (TCE) is a ubiquitous contaminant classified as a human carcinogen. Vinyl chloride (VC) is primarily used to manufacture polyvinyl chloride and can also be a degradation product of TCE. Very few data exist on the toxicity of TCE and VC in aquatic organisms particularly at environmentally relevant concentrations. The aim of this study was to evaluate the sub-lethal effects (10 day exposure; 0.1; 1; 10 µg/L) of TCE and VC in Daphnia magna at the gene, cellular, and life-history levels. Results indicated impacts of VC on the regulation of genes related to glutathione-S-transferase (GST), juvenile hormone esterase (JHE), and the vitelline outer layer membrane protein (VMO1). On the cellular level, exposure to 0.1, 1, and 10 µg/L of VC significantly increased the activity of JHE in D. magna and TCE increased the activity of chitinase (at 1 and 10 µg/L). Results for life-history parameters indicated a possible tendency of TCE to affect the number of molts at the individual level in D. magna (p=0.051). Measurement of VG-like proteins using the alkali-labile phosphates (ALP) assay did not show differences between TCE treated organisms and controls. However, semi-quantitative measurement using gradient gel electrophoresis (213-218 kDa) indicated significant decrease in VG-like protein levels following exposure to TCE at all three concentrations. Overall, results indicate effects of TCE and VC on genes and proteins related to metabolism, reproduction, and growth in D. magna. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

Numerical simulation of transport and sequential biodegradation of chlorinated aliphatic hydrocarbons using CHAIN_2D

NASA Astrophysics Data System (ADS)

Schaerlaekens, J.; Mallants, D.; Imûnek, J.; van Genuchten, M. Th.; Feyen, J.

1999-12-01

Microbiological degradation of perchloroethylene (PCE) under anaerobic conditions follows a series of chain reactions, in which, sequentially, trichloroethylene (TCE), cis-dichloroethylene (c-DCE), vinylchloride (VC) and ethene are generated. First-order degradation rate constants, partitioning coefficients and mass exchange rates for PCE, TCE, c-DCE and VC were compiled from the literature. The parameters were used in a case study of pump-and-treat remediation of a PCE-contaminated site near Tilburg, The Netherlands. Transport, non-equilibrium sorption and biodegradation chain processes at the site were simulated using the CHAIN_2D code without further calibration. The modelled PCE compared reasonably well with observed PCE concentrations in the pumped water. We also performed a scenario analysis by applying several increased reductive dechlorination rates, reflecting different degradation conditions (e.g. addition of yeast extract and citrate). The scenario analysis predicted considerably higher concentrations of the degradation products as a result of enhanced reductive dechlorination of PCE. The predicted levels of the very toxic compound VC were now an order of magnitude above the maximum permissible concentration levels.

Enhanced reactivity of nanoscale iron particles through a vacuum annealing process

NASA Astrophysics Data System (ADS)

Riba, Olga; Barnes, Robert J.; Scott, Thomas B.; Gardner, Murray N.; Jackman, Simon A.; Thompson, Ian P.

2011-10-01

A reactivity study was undertaken to compare and assess the rate of dechlorination of chlorinated aliphatic hydrocarbons (CAHs) by annealed and non-annealed nanoscale iron particles. The current study aims to resolve the uncertainties in recently published work studying the effect of the annealing process on the reduction capability of nanoscale Fe particles. Comparison of the normalized rate constants (m2/h/L) obtained for dechlorination reactions of trichloroethene (TCE) and cis-1,2-dichloroethene (cis-1,2-DCE) indicated that annealing nanoscale Fe particles increases their reactivity 30-fold. An electron transfer reaction mechanism for both types of nanoscale particles was found to be responsible for CAH dechlorination, rather than a reduction reaction by activated H2 on the particle surface (i.e., hydrogenation, hydrogenolysis). Surface analysis of the particulate material using X-ray diffraction (XRD) and transmission electron microscopy (TEM) together with surface area measurement by Brunauer, Emmett, Teller (BET) indicate that the vacuum annealing process decreases the surface area and increases crystallinity. BET surface area analysis recorded a decrease in nanoscale Fe particle surface area from 19.0 to 4.8 m2/g and crystallite dimensions inside the particle increased from 8.7 to 18.2 nm as a result of annealing.

The Impact of FeS Mineralogy on TCE Degradation

EPA Science Inventory

Iron- and sulfate-reducing conditions are often encountered in permeable reactive barrier (PRB) systems that are constructed to remove TCE from groundwater, which usually leads to the accumulation of FeS mineral phases in the matrix of the PRB. Poorly crystalline mackinawite (Fe...

Dechlorination of Polychlorinated Biphenyls by Pd/Mg Bimetallic Corrosion Nano-Cells

EPA Science Inventory

Polychlorinated biphenyls (PCBs), manufactured until mid-1970's for use as electrical insulators, were banned in 1979 due to their toxicity and persistence in the environment (1). Dechlorination of PCBs using bimetallic systems is a promising technology wherein enhanced corrosio...

INHIBITION OF REDUCTIVE DECHLORINATION BY SULFATE REDUCTION IN MICROCOSMS (ABSTRACT ONLY)

EPA Science Inventory

High sulfate (>1,000 mg/L) concentrations are potentially problematic for field implementation of in situ bioremediation of chlorinated ethenes because its reduction competes for electron donor with reductive dechlorination. As a result of this competition, reductive dechl...

Flowpath independent monitoring of reductive dechlorination potential in a fractured rock aquifer

USGS Publications Warehouse

Bradley, P.M.; Lacombe, P.J.; Imbrigiotta, T.E.; Chapelle, F.H.; Goode, D.J.

2009-01-01

The flowpath dependent approaches that are typically employed to assess biodegradation of chloroethene contaminants in unconsolidated aquifers are problematic in fractured rock settings, due to difficulties defining discrete groundwater flowpaths in such systems. In this study, the variation in the potential for chloroethene biodegradation with depth was evaluated in a fractured rock aquifer using two flowpath independent lines of field evidence: (1) the presence of the three biochemical prerequisites [electron donor(s), chloroethene electron acceptor(s), and chlororespiring microorganism(s)] for efficient chloroethene chlororespiration and (2) the in situ accumulation of chloroethene reductive dechlorination daughter products. The validity of this approach was assessed by comparing field results with the results of [1, 2- 14C] cis-DCE microcosm experiments. Microcosms were prepared with depth-specific core material, which was crushed and emplaced in discrete packer intervals for 1 year to allow colonization by the indigenous microbial community. Packer intervals characterized by significant electron donor concentrations, elevated numbers of chlororespiring microorganisms, and high reductive dechlorination product to parent contaminant ratios correlated well with the production of 14C-labeled reductive dechlorination products in the microcosm experiments. These results indicate that, in the absence of information on discrete groundwater flowpaths, a modified approach emphasizing flowpath independent lines of evidence can provide insight into the temporal and spatial variability of contaminant biodegradation in fractured rock systems. ?? 2009 National Ground Water Association.

The Microbial Degradation of TCE (Trichloroethylene).

DTIC Science & Technology

1987-04-01

enrichment studies . All the sample flasks , including the controls, contained 14C in the 14C02 trap. The 14C measured in the control flask 14C02...layer compared to the controls. These data again suggested that TCE was being biologically modified. Those flasks flushed with air gave the first hard...only slightly soluble in water. All culture flasks were incubated at 250C for a minimum of a week. Results in the carbon and nitrogen source studies are

IRIS Toxicological Review of Trichloroethylene (TCE) ...

EPA Pesticide Factsheets

EPA is conducting a peer review and public comment of the scientific basis supporting the human health hazard and dose-response assessment of Trichloroethylene (TCE) that when finalized will appear on the Integrated Risk Information System (IRIS) database. The purpose of this Toxicological Review is to provide scientific support and rationale for the hazard and dose-response assessment in IRIS pertaining to chronic exposure to trichloroethylene. It is not intended to be a comprehensive treatise on the chemical or toxicological nature of trichloroethylene.

A global historical data set of tropical cyclone exposure (TCE-DAT)

NASA Astrophysics Data System (ADS)

Geiger, Tobias; Frieler, Katja; Bresch, David N.

2018-01-01

Tropical cyclones pose a major risk to societies worldwide, with about 22 million directly affected people and damages of USD 29 billion on average per year over the last 20 years. While data on observed cyclones tracks (location of the center) and wind speeds are publicly available, these data sets do not contain information about the spatial extent of the storm and people or assets exposed. Here, we apply a simplified wind field model to estimate the areas exposed to wind speeds above 34, 64, and 96 knots (kn). Based on available spatially explicit data on population densities and gross domestic product (GDP) we estimate (1) the number of people and (2) the sum of assets exposed to wind speeds above these thresholds accounting for temporal changes in historical distribution of population and assets (TCE-hist) and assuming fixed 2015 patterns (TCE-2015). The associated spatially explicit and aggregated country-event-level exposure data (TCE-DAT) cover the period 1950 to 2015 and are freely available at https://doi.org/10.5880/pik.2017.011 (Geiger at al., 2017c). It is considered key information to (1) assess the contribution of climatological versus socioeconomic drivers of changes in exposure to tropical cyclones, (2) estimate changes in vulnerability from the difference in exposure and reported damages and calibrate associated damage functions, and (3) build improved exposure-based predictors to estimate higher-level societal impacts such as long-term effects on GDP, employment, or migration. We validate the adequateness of our methodology by comparing our exposure estimate to estimated exposure obtained from reported wind fields available since 1988 for the United States. We expect that the free availability of the underlying model and TCE-DAT will make research on tropical cyclone risks more accessible to non-experts and stakeholders.

Kinetic research on dechlorinating dichlorobenzene in aqueous system by nano-scale nickel/iron loaded with CMC/NFC hydrogel.

PubMed

Wan, Xiao-Fang; Guo, Congbao; Liu, Yu; Chai, Xin-Sheng; Li, Youming; Chen, Guangxue

2018-03-01

In this study, we reported on the nano-scale nickel/iron particles loaded in carboxymethyl/nanofibrillated cellulose (CMC/NFC) hydrogel for the dechlorination of o-dichlorobenzene (DCB) in aqueous solution. The biodegradable hydrogel may provide an ideal supporting material for fastening the bimetallic nano-scale particles, which was examined and characterized by TEM, SEM-EDX, FT-IR and BET. The performance of the selected bimetallic particles was evaluated by conducting the dechlorination of DCB in the solution under different reaction conditions (e.g., pH, dosage of nickel/iron nanoparticles and temperature). The results showed that about 70% of DCB could be dechlorinated at 20 °C in 8 h, which indicated that the immobilized reactive material had a high reduction activity when Ni/Fe loading dosage in the hydrogel (18 wt%) was considered. Moreover, the reduction behavior agreed to the pseudo-first order reaction, in which the dechlorination rate was irrelative to the pH aqueous solution. A kinetic model for predicting the concentration of DCB during the reduction reaction was established based on the experimental data. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of aging and oxidation of palladized iron embedded in activated carbon on the dechlorination of 2-chlorobiphenyl

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

Hyeok Choi; Souhail R. Al-Abed; Shirish Agarwal

2009-06-15

Reactive activated carbon (RAC) impregnated with palladized iron has been developed to effectively treat polychlorinated biphenyls (PCBs) in the environment by coupling adsorption and dechlorination of PCBs. In this study, we addressed the dechlorination reactivity and capacity of RAC toward aqueous 2-chlorobiphenyl (2-ClBP), and its aging and longevity under various oxidizing environments. RAC containing 14.4% Fe and 0.68% Pd used in this study could adsorb 122.6 mg 2-ClBP/g RAC, and dechlorinate 56.5 mg 2-ClBP/g RAC which corresponds to 12% (yield) of its estimated dechlorination capacity. Due to Fe0 oxidation to form oxide passivating layers, Fe{sub 2}O{sub 3}/Fe{sub 3}O{sub 4} (oxide-watermore » interface) and FeOOH/FeO (oxide-metal interface), RAC reactivity decreased progressively over aging under N{sub 2} < H{sub 2}O + N{sub 2} < H{sub 2}O + O{sub 2} conditions. Considering nanoscale Fe/Pd corrosion chemistry, the decline was quite slow at only 5.6%, 19.5%, and 32.5% over one year, respectively. Dissolved oxygen played a crucial role in enhancing 2-ClBP adsorption but inhibiting its dechlorination. The reactivity change could be explained with the properties of the aged RAC including surface area, Fe0 content, and Fe species. During the aging and oxidation, the RAC showed limited dissolution of Fe and Pd. Finally, implementation issues regarding application of RAC system to contaminated sites are discussed. 25 refs., 6 figs., 1 tab.« less

Evaluation of Performance and Costs Associated with Anaerobic Dechlorination Techniques. Phase 1 Site Survey, Rev 2

DTIC Science & Technology

2002-12-01

OF ORGANIC SUBSTRATES USED FOR ANAEROBIC DECHLORINATION Substrate Bulk Price per Pound (dollars) Advantages Disadvantages Sugar ( Corn Syrup ...that have been added to stimulate dechlorination reactions in the subsurface include: lactate, butyrate, acetate, molasses, refined sugars ( fructose ...1 11 3 Butyrate 3 3 1 3 2 3 3 0 Molasses 19 15 7 9 5 0 9 9 Fructose 1 1 0 1 0 0 1 0 Lactose 1 1 1 1 1 0 0 1 Acetate 3 3 1 2 1 0 3 0 Methanol/Acetate

Electrospun and functionalized PVDF/PAN nanocatalyst-loaded composite for dechlorination and photodegradation of pesticides in contaminated water.

PubMed

Nthumbi, Richard M; Ngila, Jane C

2016-10-01

A novel approach for the electrospinning and functionalization of nanocatalyst-loaded polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN) composite grafted with acrylic acid (AA; which form polyacrylic acid (PAA) brush) and decorated with silver (Ag/PAN/PVDF-g-PAA-TiO 2 /Fe-Pd) designed for the dechlorination and photodegradation of pesticides was carried out. PAN was used both as a nitrogen dopant as well as a co-polymer. Smooth nanofibers were obtained by electrospinning a solution of 12:2 wt.% PVDF/PAN blend using dimethylformamide (DMF) as solvent. The nanofibers were grafted with AA by free-radical polymerization using 2,2'azobis(2-methylpropionitrile) (AIBN) as initiator. Both bimetallic iron-palladium (Fe-Pd) and titania (TiO 2 ) nanoparticles (NP) were anchored on the grafted nanofibers via the carboxylate groups by in situ and ex situ synthesis. The Fe-Pd and nitrogen-doped TiO 2 nanoparticles were subsequently used for dechlorination and oxidation of target pollutants (dieldrin, chlorpyrifos, diuron, and fipronil) to benign products. Structural and chemical characterizations of the composites were done using various techniques. These include surface area and porosity analyzer (ASAP) using the technique by Brunner Emmett Teller (BET), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM) analyses were done. After dechlorination, the transformation products (TPs) for dieldrin, chlorpyrifos, diuron, and fipronil were obtained and identified using two-dimensional gas chromatography (time-of-flight) with a mass spectrometer detector (GCxGC-TOFMS). Analysis of total organic carbon (TOC) was carried out and used to extrapolate percentage mineralization. Experimental results showed that dechlorination efficiencies of 96, 93, 96, and 90 % for 1, 2, 2, and 3 h treatment period were respectively achieved for 5 ppm solutions of dieldrin, chlorpyrifos, diuron, and fipronil. The

Biodegradation of chlorinated ethenes at a karst site in middle Tennessee

USGS Publications Warehouse

Byl, Thomas Duane; Williams, Shannon D.

2000-01-01

This report presents results of field and laboratory investigations examining the biodegradation of chlorinated ethenes in a karst aquifer contaminated with trichloroethylene (TCE). The study site, located in Middle Tennessee, was selected because of the presence of TCE degradation byproducts in the karst aquifer and available site hydrologic and chlorinated-ethene information. Additional chemical, biological, and hydrologic data were gathered to evaluate whether the occurrence of TCE degradation byproducts in the karst aquifer was the result of biodegradation within the aquifer or simply transport into the aquifer. Geochemical analysis established that sulfate-reducing conditions, essential for reductive dechlorination of chlorinated solvents, existed in parts of the contaminated karst aquifer. Other areas of the aquifer fluctuated between anaerobic and aerobic conditions and contained compounds associated with cometabolism, such as ethane, methane, ammonia, and dissolved oxygen. A large, diverse bacteria population inhabits the contaminated aquifer. Bacteria known to biodegrade TCE and other chlorinated solvents, such as sulfate-reducers, methanotrophs, and ammonia-oxidizers, were identified from karst-aquifer water using the RNA-hybridization technique. Results from microcosms using raw karst-aquifer water found that aerobic cometabolism and anaerobic reductive-dechlorination degradation processes were possible when appropriate conditions were established in the microcosms. These chemical and biological results provide circumstantial evidence that several biodegradation processes are active in the aquifer. Additional site hydrologic information was developed to determine if appropriate conditions persist long enough in the karst aquifer for these biodegradation processes to be significant. Continuous monitoring devices placed in four wells during the spring of 1998 indicated that pH, specific conductance, dissolved oxygen, and oxidation-reduction potentials

Transformation efficiency and formation of transformation products during photochemical degradation of TCE and PCE at micromolar concentrations

PubMed Central

2014-01-01

Background Trichloroethene and tetrachloroethene are the most common pollutants in groundwater and two of the priority pollutants listed by the U.S. Environmental Protection Agency. In previous studies on TCE and PCE photolysis and photochemical degradation, concentration ranges exceeding environmental levels by far with millimolar concentrations of TCE and PCE have been used, and it is not clear if the obtained results can be used to explain the degradation of these contaminants at more realistic environmental concentration levels. Methods Experiments with micromolar concentrations of TCE and PCE in aqueous solution using direct photolysis and UV/H2O2 have been conducted and product formation as well as transformation efficiency have been investigated. SPME/GC/MS, HPLC/UV and ion chromatography with conductivity detection have been used to determine intermediates of degradation. Results The results showed that chloride was a major end product in both TCE and PCE photodegradation. Several intermediates such as formic acid, dichloroacetic acid, dichloroacetaldehyede, chloroform, formaldehyde and glyoxylic acid were formed during both, UV and UV/H2O2 treatment of TCE. However chloroacetaldehyde and chloroacetic acid were only detected during direct UV photolysis of TCE and oxalic acid was only formed during the UV/H2O2 process. For PCE photodegradation, formic acid, di- and trichloroacetic acids were detected in both UV and UV/H2O2 systems, but formaldehyde and glyoxylic acid were only detected during direct UV photolysis. Conclusions For water treatment UV/H2O2 seems to be favorable over direct UV photolysis because of its higher degradation efficiency and lower risk for the formation of harmful intermediates. PMID:24401763

Transformation efficiency and formation of transformation products during photochemical degradation of TCE and PCE at micromolar concentrations.

PubMed

Dobaradaran, Sina; Lutze, Holger; Mahvi, Amir Hossein; Schmidt, Torsten C

2014-01-08

Trichloroethene and tetrachloroethene are the most common pollutants in groundwater and two of the priority pollutants listed by the U.S. Environmental Protection Agency. In previous studies on TCE and PCE photolysis and photochemical degradation, concentration ranges exceeding environmental levels by far with millimolar concentrations of TCE and PCE have been used, and it is not clear if the obtained results can be used to explain the degradation of these contaminants at more realistic environmental concentration levels. Experiments with micromolar concentrations of TCE and PCE in aqueous solution using direct photolysis and UV/H2O2 have been conducted and product formation as well as transformation efficiency have been investigated. SPME/GC/MS, HPLC/UV and ion chromatography with conductivity detection have been used to determine intermediates of degradation. The results showed that chloride was a major end product in both TCE and PCE photodegradation. Several intermediates such as formic acid, dichloroacetic acid, dichloroacetaldehyede, chloroform, formaldehyde and glyoxylic acid were formed during both, UV and UV/H2O2 treatment of TCE. However chloroacetaldehyde and chloroacetic acid were only detected during direct UV photolysis of TCE and oxalic acid was only formed during the UV/H2O2 process. For PCE photodegradation, formic acid, di- and trichloroacetic acids were detected in both UV and UV/H2O2 systems, but formaldehyde and glyoxylic acid were only detected during direct UV photolysis. For water treatment UV/H2O2 seems to be favorable over direct UV photolysis because of its higher degradation efficiency and lower risk for the formation of harmful intermediates.

Using slow-release permanganate candles to remove TCE from a low permeable aquifer at a former landfill.

PubMed

Christenson, Mark D; Kambhu, Ann; Comfort, Steve D

2012-10-01

Past disposal of industrial solvents into unregulated landfills is a significant source of groundwater contamination. In 2009, we began investigating a former unregulated landfill with known trichloroethene (TCE) contamination. Our objective was to pinpoint the location of the plume and treat the TCE using in situ chemical oxidation (ISCO). We accomplished this by using electrical resistivity imaging (ERI) to survey the landfill and map the subsurface lithology. We then used the ERI survey maps to guide direct push groundwater sampling. A TCE plume (100-600 μg L(-1)) was identified in a low permeable silty-clay aquifer (K(h)=0.5 md(-1)) that was within 6m of ground surface. To treat the TCE, we manufactured slow-release potassium permanganate candles (SRPCs) that were 91.4 cm long and either 5. cm or 7.6 cm in dia. For comparison, we inserted equal masses of SRPCs (7.6-cm versus 5.1-cm dia) into the low permeable aquifer in staggered rows that intersected the TCE plume. The 5.1-cm dia candles were inserted using direct push rods while the 7.6-cm SRPCs were placed in 10 permanent wells. Pneumatic circulators that emitted small air bubbles were placed below the 7.6-cm SRPCs in the second year. Results 15 months after installation showed significant TCE reductions in the 7.6-cm candle treatment zone (67-85%) and between 10% and 66% decrease in wells impacted by the direct push candles. These results support using slow-release permanganate candles as a means of treating chlorinated solvents in low permeable aquifers. Copyright © 2012 Elsevier Ltd. All rights reserved.

Morphological characteristics of polyvinyl chloride (PVC) dechlorination during pyrolysis process: Influence of PVC content and heating rate.

PubMed

Cao, Qiongmin; Yuan, Guoan; Yin, Lijie; Chen, Dezhen; He, Pinjing; Wang, Hai

2016-12-01

In this research morphological techniques were used to characterize dechlorination process of PVC when it is in the mixed waste plastics and the two important factors influencing this process, namely, the proportion of PVC in the mixed plastics and heating rate adopted in the pyrolysis process were investigated. During the pyrolysis process for the mixed plastics containing PVC, the morphologic characteristics describing PVC dechlorination behaviors were obtained with help of a high-speed infrared camera and image processing tools. At the same time emission of hydrogen chloride (HCl) was detected to find out the start and termination of HCl release. The PVC contents in the mixed plastics varied from 0% to 12% in mass and the heating rate for PVC was changed from 10 to 60°C/min. The morphologic parameters including "bubble ratio" (BR) and "pixel area" (PA) were found to have obvious features matching with PVC dechlorination process therefore can be used to characterize dechlorination of PVC alone and in the mixed plastics. It has been also found that shape of HCl emission curve is independent of PVC proportions in the mixed plastics, but shifts to right side with elevated heating rate; and all of which can be quantitatively reflected in morphologic parameters vs. temperature curves. Copyright © 2016 Elsevier Ltd. All rights reserved.

Trichloroethylene (TCE) in tree cores to complement a subsurface investigation on residential property near a former electroplating facility.

PubMed

Wilcox, Jeffrey D; Johnson, Kathy M

2016-10-01

Tree cores were collected and analyzed for trichloroethylene (TCE) on a private property between a former electroplating facility in Asheville, North Carolina (USA), and a contaminated wetland/spring complex. TCE was detected in 16 of 31 trees, the locations of which were largely consistent with a "plume core" delineated by a more detailed subsurface investigation nearly 2 years later. Concentrations in tree cores and nearby soil borings were not correlated, perhaps due to heterogeneities in both geologic and tree root structure, spatial and temporal variability in transpiration rates, or interferences caused by other contaminants at the site. Several tree cores without TCE provided evidence for significantly lower TCE concentrations in shallow groundwater along the margins of the contaminated spring complex in an area with limited accessibility. This study demonstrates that tree core analyses can complement a more extensive subsurface investigation, particularly in residential or ecologically sensitive areas.

Microfabricated gas chromatograph for on-site determinations of TCE in indoor air arising from vapor intrusion. 2. Spatial/temporal monitoring.

PubMed

Kim, Sun Kyu; Burris, David R; Bryant-Genevier, Jonathan; Gorder, Kyle A; Dettenmaier, Erik M; Zellers, Edward T

2012-06-05

We demonstrate the use of two prototype Si-microfabricated gas chromatographs (μGC) for continuous, short-term measurements of indoor trichloroethylene (TCE) vapor concentrations related to the investigation of TCE vapor intrusion (VI) in two houses. In the first house, with documented TCE VI, temporal variations in TCE air concentrations were monitored continuously for up to 48 h near the primary VI entry location under different levels of induced differential pressure (relative to the subslab). Concentrations ranged from 0.23 to 27 ppb by volume (1.2-150 μg/m(3)), and concentration trends agreed closely with those determined from concurrent reference samples. The sensitivity and temporal resolution of the measurements were sufficiently high to detect transient fluctuations in concentration resulting from short-term changes in variables affecting the extent of VI. Spatial monitoring showed a decreasing TCE concentration gradient with increasing distance from the primary VI entry location. In the second house, with no TCE VI, spatial profiles derived from the μGC prototype data revealed an intentionally hidden source of TCE within a closet, demonstrating the capability for locating non-VI sources. Concentrations measured in this house ranged from 0.51 to 56 ppb (2.7-300 μg/m(3)), in good agreement with reference method values. This first field demonstration of μGC technology for automated, near-real-time, selective VOC monitoring at low- or subppb levels augurs well for its use in short- and long-term on-site analysis of indoor air in support of VI assessments.

Threshold amounts of organic carbon needed to initiate reductive dechlorination in groundwater systems

USGS Publications Warehouse

Chapelle, Francis H.; Thomas, Lashun K.; Bradley, Paul M.; Rectanus, Heather V.; Widdowson, Mark A.

2012-01-01

Aquifer sediment and groundwater chemistry data from 15 Department of Defense facilities located throughout the United States were collected and analyzed with the goal of estimating the amount of natural organic carbon needed to initiate reductive dechlorination in groundwater systems. Aquifer sediments were analyzed for hydroxylamine and NaOH-extractable organic carbon, yielding a probable underestimate of potentially bioavailable organic carbon (PBOC). Aquifer sediments were also analyzed for total organic carbon (TOC) using an elemental combustion analyzer, yielding a probable overestimate of bioavailable carbon. Concentrations of PBOC correlated linearly with TOC with a slope near one. However, concentrations of PBOC were consistently five to ten times lower than TOC. When mean concentrations of dissolved oxygen observed at each site were plotted versus PBOC, it showed that anoxic conditions were initiated at approximately 200 mg/kg of PBOC. Similarly, the accumulation of reductive dechlorination daughter products relative to parent compounds increased at a PBOC concentration of approximately 200 mg/kg. Concentrations of total hydrolysable amino acids (THAA) in sediments also increased at approximately 200 mg/kg, and bioassays showed that sediment CO2 production correlated positively with THAA. The results of this study provide an estimate for threshold amounts of bioavailable carbon present in aquifer sediments (approximately 200 mg/kg of PBOC; approximately 1,000 to 2,000 mg/kg of TOC) needed to support reductive dechlorination in groundwater systems.

Architecture, persistence and dissolution of a 20 to 45 year old trichloroethene DNAPL source zone

NASA Astrophysics Data System (ADS)

Rivett, Michael O.; Dearden, Rachel A.; Wealthall, Gary P.

2014-12-01

A detailed field-scale investigation of processes controlling the architecture, persistence and dissolution of a 20 to 45 year old trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) source zone located within a heterogeneous sand/gravel aquifer at a UK industrial site is presented. The source zone was partially enclosed by a 3-sided cell that allowed detailed longitudinal/fence transect monitoring along/across a controlled streamtube of flow induced by an extraction well positioned at the cell closed end. Integrated analysis of high-resolution DNAPL saturation (Sn) (from cores), dissolved-phase plume concentration (from multilevel samplers), tracer test and permeability datasets was undertaken. DNAPL architecture was determined from soil concentration data using partitioning calculations. DNAPL threshold soil concentrations and low Sn values calculated were sensitive to sorption assumptions. An outcome of this was the uncertainty in demarcation of secondary source zone diffused and sorbed mass that is distinct from trace amounts of low Sn DNAPL mass. The majority of source mass occurred within discrete lenses or pools of DNAPL associated with low permeability geological units. High residual saturation (Sn > 10-20%) and pools (Sn > 20%) together accounted for almost 40% of the DNAPL mass, but only 3% of the sampled source volume. High-saturation DNAPL lenses/pools were supported by lower permeability layers, but with DNAPL still primarily present within slightly more permeable overlying units. These lenses/pools exhibited approximately linearly declining Sn profiles with increasing elevation ascribed to preferential dissolution of the uppermost DNAPL. Bi-component partitioning calculations on soil samples confirmed that the dechlorination product cDCE (cis-dichloroethene) was accumulating in the TCE DNAPL. Estimated cDCE mole fractions in the DNAPL increased towards the DNAPL interface with the uppermost mole fraction of 0.04 comparable to literature

Architecture, persistence and dissolution of a 20 to 45 year old trichloroethene DNAPL source zone.

PubMed

Rivett, Michael O; Dearden, Rachel A; Wealthall, Gary P

2014-12-01

A detailed field-scale investigation of processes controlling the architecture, persistence and dissolution of a 20 to 45year old trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) source zone located within a heterogeneous sand/gravel aquifer at a UK industrial site is presented. The source zone was partially enclosed by a 3-sided cell that allowed detailed longitudinal/fence transect monitoring along/across a controlled streamtube of flow induced by an extraction well positioned at the cell closed end. Integrated analysis of high-resolution DNAPL saturation (Sn) (from cores), dissolved-phase plume concentration (from multilevel samplers), tracer test and permeability datasets was undertaken. DNAPL architecture was determined from soil concentration data using partitioning calculations. DNAPL threshold soil concentrations and low Sn values calculated were sensitive to sorption assumptions. An outcome of this was the uncertainty in demarcation of secondary source zone diffused and sorbed mass that is distinct from trace amounts of low Sn DNAPL mass. The majority of source mass occurred within discrete lenses or pools of DNAPL associated with low permeability geological units. High residual saturation (Sn>10-20%) and pools (Sn>20%) together accounted for almost 40% of the DNAPL mass, but only 3% of the sampled source volume. High-saturation DNAPL lenses/pools were supported by lower permeability layers, but with DNAPL still primarily present within slightly more permeable overlying units. These lenses/pools exhibited approximately linearly declining Sn profiles with increasing elevation ascribed to preferential dissolution of the uppermost DNAPL. Bi-component partitioning calculations on soil samples confirmed that the dechlorination product cDCE (cis-dichloroethene) was accumulating in the TCE DNAPL. Estimated cDCE mole fractions in the DNAPL increased towards the DNAPL interface with the uppermost mole fraction of 0.04 comparable to literature laboratory

FRACTIONATION OF STABLE CARBON ISOTOPES DURING ABIOTIC TRANSFORMATION OF TCE

EPA Science Inventory

At a Superfund Site in Minnesota, ground water is contaminated with trichloroethylene (TCE) with the contaminant plume stretching over five miles long. The ground water is iron and manganese reducing, and the complete absence of dichloroethylene, vinyl chloride, and ethene in th...

Effect of toluene concentration and hydrogen peroxide on Pseudomonas plecoglossicida cometabolizing mixture of cis-DCE and TCE in soil slurry.

PubMed

Li, Junhui; Lu, Qihong; de Toledo, Renata Alves; Lu, Ying; Shim, Hojae

2015-12-01

An indigenous Pseudomonas sp., isolated from the regional contaminated soil and identified as P. plecoglossicida, was evaluated for its aerobic cometabolic removal of cis-1,2-dichloroethylene (cis-DCE) and trichloroethylene (TCE) using toluene as growth substrate in a laboratory-scale soil slurry. The aerobic simultaneous bioremoval of the cis-DCE/TCE/toluene mixture was studied under different conditions. Results showed that an increase in toluene concentration level from 300 to 900 mg/kg prolonged the lag phase for the bacterial growth, while the bioremoval extent for cis-DCE, TCE, and toluene declined as the initial toluene concentration increased. In addition, the cometabolic bioremoval of cis-DCE and TCE was inhibited by the presence of hydrogen peroxide as the additional oxygen source, while the bioremoval of toluene (900 mg/kg) was enhanced after 9 days of incubation. The subsequent addition of toluene did not improve the cometabolic bioremoval of cis-DCE and TCE. The obtained results would help to enhance the applicability of bioremediation technology to the mixed waste contaminated sites.

PARTITIONING, DESORPTION, AND DECHLORINATION OF A PCB CONGENER IN SEDIMENT SLURRY SUPERNATANTS

EPA Science Inventory

Partitioning and desorption played specific roles in the dechlorination of 2-chlorobiphenyl (2-ClBP) in sediment slurry supernatants, which are suspensions of disssolved organic matter(DOM). In short-term experiments, the partition coefficient (K_p) was related to the a...

Target Organ Metabolism, Toxicity, and Mechanisms of Trichloroethylene and Perchloroethylene: Key Similarities, Differences, and Data Gaps

PubMed Central

Cichocki, Joseph A.; Guyton, Kathryn Z.; Guha, Neela; Chiu, Weihsueh A.

2016-01-01

Trichloroethylene (TCE) and perchloroethylene or tetrachloroethylene (PCE) are high–production volume chemicals with numerous industrial applications. As a consequence of their widespread use, these chemicals are ubiquitous environmental contaminants to which the general population is commonly exposed. It is widely assumed that TCE and PCE are toxicologically similar; both are simple olefins with three (TCE) or four (PCE) chlorines. Nonetheless, despite decades of research on the adverse health effects of TCE or PCE, few studies have directly compared these two toxicants. Although the metabolic pathways are qualitatively similar, quantitative differences in the flux and yield of metabolites exist. Recent human health assessments have uncovered some overlap in target organs that are affected by exposure to TCE or PCE, and divergent species- and sex-specificity with regard to cancer and noncancer hazards. The objective of this minireview is to highlight key similarities, differences, and data gaps in target organ metabolism and mechanism of toxicity. The main anticipated outcome of this review is to encourage research to 1) directly compare the responses to TCE and PCE using more sensitive biochemical techniques and robust statistical comparisons; 2) more closely examine interindividual variability in the relationship between toxicokinetics and toxicodynamics for TCE and PCE; 3) elucidate the effect of coexposure to these two toxicants; and 4) explore new mechanisms for target organ toxicity associated with TCE and/or PCE exposure. PMID:27511820

Removal of 2-ClBP from soil-water system using activated carbon supported nanoscale zerovalent iron.

PubMed

Zhang, Wei; Yu, Tian; Han, Xiaolin; Ying, Weichi

2016-09-01

We explored the feasibility and removal mechanism of removing 2-chlorobiphenyl (2-ClBP) from soil-water system using granular activated carbon (GAC) impregnated with nanoscale zerovalent iron (reactive activated carbon or RAC). The RAC samples were successfully synthesized by the liquid precipitation method. The mesoporous GAC based RAC with low iron content (1.32%) exhibited higher 2-ClBP removal efficiency (54.6%) in the water phase. The result of Langmuir-Hinshelwood kinetic model implied that the different molecular structures between 2-ClBP and trichloroethylene (TCE) resulted in more difference in dechlorination reaction rates on RAC than adsorption capacities. Compared to removing 2-ClBP in the water phase, RAC removed the 2-ClBP more slowly in the soil phase due to the significant external mass transfer resistance. However, in the soil phase, a better removal capacity of RAC was observed than its base GAC because the chemical dechlorination played a more important role in total removal process for 2-ClBP. This important result verified the effectiveness of RAC for removing 2-ClBP in the soil phase. Although reducing the total RAC removal rate of 2-ClBP, soil organic matter (SOM), especially the soft carbon, also served as an electron transfer medium to promote the dechlorination of 2-ClBP in the long term. Copyright © 2016. Published by Elsevier B.V.

Thermal dechlorination of PCB-209 over Ca species-doped Fe₂O₃.

PubMed

Su, Guijin; Huang, Linyan; Shi, Ruifang; Liu, Yexuan; Lu, Huijie; Zhao, Yuyang; Yang, Fan; Gao, Lirong; Zheng, Minghui

2016-02-01

Degradation reaction of decachlorobiphenyl (PCB-209) was investigated over the synthesized Ca species-doped Fe2O3 at 300 °C. The 1%Ca-Fe2O3 exhibited the highest activity among the four catalysts prepared with the pseudo-first order reaction at k(obs) = 0.103 min(-1). PCB-207, PCB-197, PCB-176, PCB-184, PCB-150, PCB-136, PCB-148, PCB-104, PCB-96, PCB-54, PCB-19, PCB-4 and PCB-1 were identified as the dominant isomers in their respective nonachlorobiphenyl (NonaCB) to monochlorobiphenyl (MonoCB) homologue groups. Analysis of the hydrodechlorination products indicated that dechlorination was much more favored on meta- and para-than on ortho-positions. The formation of significantly predominant NonaCB and octachlorobiphenyl (OctaCB) isomers was attributed to lower energy principles and to the 90° dihedral angles of two aromatic rings which prevented the hydrodechlorination at ortho-positions. When the number of chlorine atoms is not more than 7, the steric effect supports the formation of predominant PCB isomers having chlorines at four ortho-positions. During the dechlorination of tetrachlorobiphenyl (TetraCB) formed to generate monochlorobiphenyl (MonoCB) isomers, the chlorine atoms fully substituted at the ortho-positions have to be successively removed, with the first two dechlorinations preferentially occurring at the two different benzene rings. This is dissimilar to that of octachloronaphthalene (PCN-75) in which the hydrodechlorination reaction happened preferentially at ortho-position due to the existence of steric effects. The opposite roles of the steric effect in ortho-position between PCB-209 and PCN-75 might be due to the difference of the π-conjugated plane caused by the dihedral angle of 90° and 0° of the two aromatic rings. Copyright © 2015 Elsevier Ltd. All rights reserved.

Efficacy of controlled-release KMnO4 (CRP) for controlling dissolved TCE plume in groundwater: a large flow-tank study.

PubMed

Lee, Byung Sun; Kim, Jeong Hee; Lee, Ki Churl; Kim, Yang Bin; Schwartz, Franklin W; Lee, Eung Seok; Woo, Nam Chil; Lee, Myoung Ki

2009-02-01

A well-based, reactive barrier system using controlled-release potassium permanganate (CRP system) was recently developed as a long-term treatment option for dilute plumes of chlorinated solvents in groundwater. In this study, we performed large-scale (L x W x D = 8 m x 4 m x 2 m) flow-tank experiments to examine remedial efficacy of the CRP system. A total of 110 CRP rods (OD x L=5 cm x 150 cm) were used to construct a well-based CRP system (L x W x D = 3 m x 4 m x 1.5 m) comprising three discrete barriers installed at 1-m interval downstream. Natural sands having oxidant demand of 3.7 g MnO(4)(-)kg(-1) for 500 mg L(-1)MnO(4)(-) were used as porous media. After MnO(4)(-) concentrations were somewhat stabilized (0.5-6.0 mg L(-1)), trichloroethylene (TCE) plume was flowed through the flow-tank for 53 d by supplying 1.19 m(3)d(-1) of TCE solution. Mean initial TCE concentrations were 87 microg L(-1) for first 20 d and 172 microg L(-1) for the next 33 d. During TCE treatment, flow velocity (0.60md(-1)), pH (7.0-8.2), and concentrations of dissolved metals ([Al]=0.7 mg L(-1), [Fe]=0.01 mg L(-1)) showed little variations. The MnO(2)(s) contents in the sandy media measured after the TCE treatment ranged from 21 to 26 mg kg(-1), slightly increased from mean baseline value of 17 mg kg(-1). Strengths of the TCE plume considerably diminished by the CRP system. For the 87 microg L(-1) plume, TCE concentrations decreased by 38% (53), 67% (29), and 74% (23 microg L(-1)) after 1st, 2nd, and 3rd barriers, respectively. For the 172 microg L(-1) plume, TCE concentrations decreased by 27% (125), 46% (93), and 65% (61 microg L(-1)) after 1st, 2nd, and 3rd barriers, respectively. Incomplete destruction of TCE plume was attributed to the lack of lateral dispersion in the unpumped well-based barrier system. Development of delivery systems that can facilitate lateral spreading and mixing of permanganate with contaminant plume is warranted.

Effects of pyrolysis temperature on soybean stover- and peanut shell-derived biochar properties and TCE adsorption in water.

PubMed

Ahmad, Mahtab; Lee, Sang Soo; Dou, Xiaomin; Mohan, Dinesh; Sung, Jwa-Kyung; Yang, Jae E; Ok, Yong Sik

2012-08-01

Conversion of crop residues into biochars (BCs) via pyrolysis is beneficial to environment compared to their direct combustion in agricultural field. Biochars developed from soybean stover at 300 and 700 °C (S-BC300 and S-BC700, respectively) and peanut shells at 300 and 700 °C (P-BC300 and P-BC700, respectively) were used for the removal of trichloroethylene (TCE) from water. Batch adsorption experiments showed that the TCE adsorption was strongly dependent on the BCs properties. Linear relationships were obtained between sorption parameters (K(M) and S(M)) and molar elemental ratios as well as surface area of the BCs. The high adsorption capacity of BCs produced at 700 °C was attributed to their high aromaticity and low polarity. The efficacy of S-BC700 and P-BC700 for removing TCE from water was comparable to that of activated carbon (AC). Pyrolysis temperature influencing the BC properties was a critical factor to assess the removal efficiency of TCE from water. Copyright © 2012 Elsevier Ltd. All rights reserved.

Comment on "Photo-assisted degradation of 2, 4, 6-trichlorophenol by an advanced reduction process based on sulfite anion radical: Degradation, dechlorination and mineralization" [Chemosphere 191 (2018) 156-165].

PubMed

Tang, Min

2018-07-01

The sulfite-mediated photoreduction (SMP) with UV-C light showed promising performances especially for dechlorination of chlorinated organic compounds (e.g., 2, 4, 6-trichlorophenol (TCP)). The investigation of SMP for TCP is commented and proposed in order to clarify the mechanisms involved. Copyright © 2018 Elsevier Ltd. All rights reserved.

Coupling Aggressive Mass Removal with Microbial Reductive Dechlorination for Remediation of DNAPL Source Zones: A Review and Assessment

PubMed Central

Christ, John A.; Ramsburg, C. Andrew; Abriola, Linda M.; Pennell, Kurt D.; Löffler, Frank E.

2005-01-01

The infiltration of dense non-aqueous-phase liquids (DNAPLs) into the saturated subsurface typically produces a highly contaminated zone that serves as a long-term source of dissolved-phase groundwater contamination. Applications of aggressive physical–chemical technologies to such source zones may remove > 90% of the contaminant mass under favorable conditions. The remaining contaminant mass, however, can create a rebounding of aqueous-phase concentrations within the treated zone. Stimulation of microbial reductive dechlorination within the source zone after aggressive mass removal has recently been proposed as a promising staged-treatment remediation technology for transforming the remaining contaminant mass. This article reviews available laboratory and field evidence that supports the development of a treatment strategy that combines aggressive source-zone removal technologies with subsequent promotion of sustained microbial reductive dechlorination. Physical–chemical source-zone treatment technologies compatible with posttreatment stimulation of microbial activity are identified, and studies examining the requirements and controls (i.e., limits) of reductive dechlorination of chlorinated ethenes are investigated. Illustrative calculations are presented to explore the potential effects of source-zone management alternatives. Results suggest that, for the favorable conditions assumed in these calculations (i.e., statistical homogeneity of aquifer properties, known source-zone DNAPL distribution, and successful bioenhancement in the source zone), source longevity may be reduced by as much as an order of magnitude when physical–chemical source-zone treatment is coupled with reductive dechlorination. PMID:15811838

[Endonasal Dacryocystorhinostomy (DCR) with Transcanalicular Endoillumination (TCE) of the Saccus Lacrimalis].

PubMed

Hefner, J; Klask, J; Gerding, H

2016-04-01

Endonasal dacryocystorhinostomy (DCR) has been established as a standard procedure of lacrimal surgery, since it causes much less tissue damage than ab externo procedures. Diffiulties in visualization of the target area has been a limitation to the transnasal approach. An improvement of the classical endonasal DCR was achieved by the introduction of a transcanalicular endoillumination (TCE) of the lacrimal sac using a 23-Gauge vitreoretinal light probe, which can easily be intubated into the cannaliculi and advanced into the the lacrimal sac. Illumination of the lacrimal sac guides the endonasal approach and facilitates the creation of a lacrimal bypass. In our standard procedure a bicanalicular silicone intubation through the osteotomy is finally placed. Due to the introduction of TCE of the lacrimal sac, the surgical procedure of endonasal DCR became less traumatic and needed a significantly reduced operating time. Georg Thieme Verlag KG Stuttgart · New York.

Development of an updated PBPK model for trichloroethylene and metabolites in mice, and its application to discern the role of oxidative metabolism in TCE-induced hepatomegaly.

PubMed

Evans, M V; Chiu, W A; Okino, M S; Caldwell, J C

2009-05-01

Trichloroethylene (TCE) is a lipophilic solvent rapidly absorbed and metabolized via oxidation and conjugation to a variety of metabolites that cause toxicity to several internal targets. Increases in liver weight (hepatomegaly) have been reported to occur quickly in rodents after TCE exposure, with liver tumor induction reported in mice after long-term exposure. An integrated dataset for gavage and inhalation TCE exposure and oral data for exposure to two of its oxidative metabolites (TCA and DCA) was used, in combination with an updated and more accurate physiologically-based pharmacokinetic (PBPK) model, to examine the question as to whether the presence of TCA in the liver is responsible for TCE-induced hepatomegaly in mice. The updated PBPK model was used to help discern the quantitative contribution of metabolites to this effect. The update of the model was based on a detailed evaluation of predictions from previously published models and additional preliminary analyses based on gas uptake inhalation data in mice. The parameters of the updated model were calibrated using Bayesian methods with an expanded pharmacokinetic database consisting of oral, inhalation, and iv studies of TCE administration as well as studies of TCE metabolites in mice. The dose-response relationships for hepatomegaly derived from the multi-study database showed that the proportionality of dose to response for TCE- and DCA-induced hepatomegaly is not observed for administered doses of TCA in the studied range. The updated PBPK model was used to make a quantitative comparison of internal dose of metabolized and administered TCA. While the internal dose of TCA predicted by modeling of TCE exposure (i.e., mg TCA/kg-d) showed a linear relationship with hepatomegaly, the slope of the relationship was much greater than that for directly administered TCA. Thus, the degree of hepatomegaly induced per unit of TCA produced through TCE oxidation is greater than that expected per unit of TCA

Target Organ Metabolism, Toxicity, and Mechanisms of Trichloroethylene and Perchloroethylene: Key Similarities, Differences, and Data Gaps.

PubMed

Cichocki, Joseph A; Guyton, Kathryn Z; Guha, Neela; Chiu, Weihsueh A; Rusyn, Ivan; Lash, Lawrence H

2016-10-01

Trichloroethylene (TCE) and perchloroethylene or tetrachloroethylene (PCE) are high-production volume chemicals with numerous industrial applications. As a consequence of their widespread use, these chemicals are ubiquitous environmental contaminants to which the general population is commonly exposed. It is widely assumed that TCE and PCE are toxicologically similar; both are simple olefins with three (TCE) or four (PCE) chlorines. Nonetheless, despite decades of research on the adverse health effects of TCE or PCE, few studies have directly compared these two toxicants. Although the metabolic pathways are qualitatively similar, quantitative differences in the flux and yield of metabolites exist. Recent human health assessments have uncovered some overlap in target organs that are affected by exposure to TCE or PCE, and divergent species- and sex-specificity with regard to cancer and noncancer hazards. The objective of this minireview is to highlight key similarities, differences, and data gaps in target organ metabolism and mechanism of toxicity. The main anticipated outcome of this review is to encourage research to 1) directly compare the responses to TCE and PCE using more sensitive biochemical techniques and robust statistical comparisons; 2) more closely examine interindividual variability in the relationship between toxicokinetics and toxicodynamics for TCE and PCE; 3) elucidate the effect of coexposure to these two toxicants; and 4) explore new mechanisms for target organ toxicity associated with TCE and/or PCE exposure. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Characterization of inter-tissue and inter-strain variability of TCE glutathione conjugation metabolites DCVG, DCVC, and NAcDCVC in the mouse.

PubMed

Luo, Yu-Syuan; Furuya, Shinji; Chiu, Weihsueh; Rusyn, Ivan

2018-01-01

Trichloroethylene (TCE) is a ubiquitous environmental toxicant that is a liver and kidney carcinogen. Conjugation of TCE with glutathione (GSH) leads to formation of nepthrotoxic and mutagenic metabolites postulated to be critical for kidney cancerdevelopment; however, relatively little is known regarding their tissue levels as previous analytical methods for their detection lacked sensitivity. Here, an LC-MS/MS-based method for simultaneous detection of S-(1,2-dichlorovinyl)-glutathione (DCVG), S-(1,2-dichlorovinyl)-L-cysteine (DCVC), and N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (NAcDCVC) in multiple mouse tissues was developed. This analytical method is rapid, sensitive (limits of detection (LOD) 3-30 fmol across metabolites and tissues), and robust to quantify all three metabolites in liver, kidneys, and serum. The method was used to characterize inter-tissue and inter-strain variability in formation of conjugative metabolites of TCE. Single oral dose of TCE (24, 240 or 800 mg/kg) was administered to male mice from 20 inbred strains of Collaborative Cross. Inter-strain variability in the levels of DCVG, DCVC, and NAcDCVC (GSD = 1.6-2.9) was observed. Whereas NAcDCVC was distributed equally among analyzed tissues, highest levels of DCVG were detected in liver and DCVC in kidneys. Evidence indicated that inter-strain variability in conjugative metabolite formation of TCE might affect susceptibility to adverse health effects and that this method might aid in filling data gaps in human health assessment of TCE.

Analysis of sources of bulk conductivity change in saturated silica sand after unbuffered TCE oxidation by permanganate.

PubMed

Hort, Ryan D; Revil, André; Munakata-Marr, Junko

2014-09-01

Time lapse resistivity surveys could potentially improve monitoring of permanganate-based in situ chemical oxidation (ISCO) of organic contaminants such as trichloroethene (TCE) by tracking changes in subsurface conductivity that result from injection of permanganate and oxidation of the contaminant. Bulk conductivity and pore fluid conductivity changes during unbuffered TCE oxidation using permanganate are examined through laboratory measurements and conductivity modeling using PHREEQC in fluid samples and porous media samples containing silica sand. In fluid samples, oxidation of one TCE molecule produces three chloride ions and one proton, resulting in an increase in fluid electrical conductivity despite the loss of two permanganate ions in the reaction. However, in saturated sand samples in which up to 8mM TCE was oxidized, at least 94% of the fluid conductivity associated with the presence of protons was removed within 3h of sand contact, most likely through protonation of silanol groups found on the surface of the sand grains. Minor conductivity effects most likely associated with pH-dependent reductive dissolution of manganese dioxide were also observed but not accounted for in pore-fluid conductivity modeling. Unaccounted conductivity effects resulted in an under-calculation of post-reaction pore fluid conductivity of 2.1% to 5.5%. Although small increases in the porous media formation factor resulting from precipitation of manganese dioxide were detected (about 3%), these increases could not be confirmed to be statistically significant. Both injection of permanganate and oxidation of TCE cause increases in bulk conductivity that would be detectable through time-lapse resistivity surveys in field conditions. Copyright © 2014 Elsevier B.V. All rights reserved.

PILOT-SCALE EVALUATION OF THE IRON-ENHANCED DECHLORINATION TECHNOLOGY FOR REMEDIATION OF CONTAMINATED GROUNDWATER

EPA Science Inventory

An iron-enhanced dechlorination technology was evaluated, under the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation (SITE) program, at a contaminated printed circuit board manufacturing site in New Jersey. This paper describes the feasibility...

Organohalide Respiration with Chlorinated Ethenes under Low pH Conditions

DOE PAGES

Yang, Yi; Cápiro, Natalie L.; Marcet, Tyler F.; ...

2017-06-30

Bioremediation at chlorinated solvent sites often leads to groundwater acidification due to electron donor fermentation and enhanced dechlorination activity. The microbial reductive dechlorination process is robust at circumneutral pH, but activity declines at groundwater pH values below 6.0. Consistent with this observation, the activity of tetrachloroethene (PCE) dechlorinating cultures declined at pH 6.0 and was not sustained in pH 5.5 medium, with one notable exception. Sulf urospirillum multivorans dechlorinated PCE to cis-1,2-dichloroethene (cDCE) in pH 5.5 medium and maintained this activity upon repeated transfers. Microcosms established with soil and aquifer materials from five distinct locations dechlorinated PCE-to-ethene at pH 5.5more » and pH 7.2. Dechlorination to ethene was maintained following repeated transfers at pH 7.2, but no ethene was produced at pH 5.5, and only the transfer cultures derived from the Axton Cross Superfund (ACS) microcosms sustained PCE dechlorination to cDCE as a final product. 16S rRNA gene amplicon sequencing of pH 7.2 and pH 5.5 ACS enrichments revealed distinct microbial communities, with the dominant dechlorinator being Dehalococcoides in pH 7.2 and Sulf urospirillum in pH 5.5 cultures. PCE-to-trichloroethene- (TCE-) and PCE-to-cDCEdechlorinating isolates obtained from the ACS pH 5.5 enrichment shared 98.6%, and 98.5% 16S rRNA gene sequence similarities to Sulf urospirillum multivorans. Lastly, these findings imply that sustained Dehalococcoides activity cannot be expected in low pH (i.e., ≤ 5.5) groundwater, and organohalide-respiring Sulf urospirillum spp. are key contributors to in situ PCE reductive dechlorination under low pH conditions.« less

Organohalide Respiration with Chlorinated Ethenes under Low pH Conditions

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

Yang, Yi; Cápiro, Natalie L.; Marcet, Tyler F.

Bioremediation at chlorinated solvent sites often leads to groundwater acidification due to electron donor fermentation and enhanced dechlorination activity. The microbial reductive dechlorination process is robust at circumneutral pH, but activity declines at groundwater pH values below 6.0. Consistent with this observation, the activity of tetrachloroethene (PCE) dechlorinating cultures declined at pH 6.0 and was not sustained in pH 5.5 medium, with one notable exception. Sulf urospirillum multivorans dechlorinated PCE to cis-1,2-dichloroethene (cDCE) in pH 5.5 medium and maintained this activity upon repeated transfers. Microcosms established with soil and aquifer materials from five distinct locations dechlorinated PCE-to-ethene at pH 5.5more » and pH 7.2. Dechlorination to ethene was maintained following repeated transfers at pH 7.2, but no ethene was produced at pH 5.5, and only the transfer cultures derived from the Axton Cross Superfund (ACS) microcosms sustained PCE dechlorination to cDCE as a final product. 16S rRNA gene amplicon sequencing of pH 7.2 and pH 5.5 ACS enrichments revealed distinct microbial communities, with the dominant dechlorinator being Dehalococcoides in pH 7.2 and Sulf urospirillum in pH 5.5 cultures. PCE-to-trichloroethene- (TCE-) and PCE-to-cDCEdechlorinating isolates obtained from the ACS pH 5.5 enrichment shared 98.6%, and 98.5% 16S rRNA gene sequence similarities to Sulf urospirillum multivorans. Lastly, these findings imply that sustained Dehalococcoides activity cannot be expected in low pH (i.e., ≤ 5.5) groundwater, and organohalide-respiring Sulf urospirillum spp. are key contributors to in situ PCE reductive dechlorination under low pH conditions.« less

Microbially enhanced dissolution and reductive dechlorination of PCE by a mixed culture: Model validation and sensitivity analysis

NASA Astrophysics Data System (ADS)

Chen, Mingjie; Abriola, Linda M.; Amos, Benjamin K.; Suchomel, Eric J.; Pennell, Kurt D.; Löffler, Frank E.; Christ, John A.

2013-08-01

Reductive dechlorination catalyzed by organohalide-respiring bacteria is often considered for remediation of non-aqueous phase liquid (NAPL) source zones due to cost savings, ease of implementation, regulatory acceptance, and sustainability. Despite knowledge of the key dechlorinators, an understanding of the processes and factors that control NAPL dissolution rates and detoxification (i.e., ethene formation) is lacking. A recent column study demonstrated a 5-fold cumulative enhancement in tetrachloroethene (PCE) dissolution and ethene formation (Amos et al., 2009). Spatial and temporal monitoring of key geochemical and microbial (i.e., Geobacter lovleyi and Dehalococcoides mccartyi strains) parameters in the column generated a data set used herein as the basis for refinement and testing of a multiphase, compositional transport model. The refined model is capable of simulating the reactive transport of multiple chemical constituents produced and consumed by organohalide-respiring bacteria and accounts for substrate limitations and competitive inhibition. Parameter estimation techniques were used to optimize the values of sensitive microbial kinetic parameters, including maximum utilization rates, biomass yield coefficients, and endogenous decay rates. Comparison and calibration of model simulations with the experimental data demonstrate that the model is able to accurately reproduce measured effluent concentrations, while delineating trends in dechlorinator growth and reductive dechlorination kinetics along the column. Sensitivity analyses performed on the optimized model parameters indicate that the rates of PCE and cis-1,2-dichloroethene (cis-DCE) transformation and Dehalococcoides growth govern bioenhanced dissolution, as long as electron donor (i.e., hydrogen flux) is not limiting. Dissolution enhancements were shown to be independent of cis-DCE accumulation; however, accumulation of cis-DCE, as well as column length and flow rate (i.e., column residence time

Electrochemically induced dual reactive barriers for transformation of TCE and mixture of contaminants in groundwater.

PubMed

Mao, Xuhui; Yuan, Songhu; Fallahpour, Noushin; Ciblak, Ali; Howard, Joniqua; Padilla, Ingrid; Loch-Caruso, Rita; Alshawabkeh, Akram N

2012-11-06

A novel reactive electrochemical flow system consisting of an iron anode and a porous cathode is proposed for the remediation of mixture of contaminants in groundwater. The system consists of a series of sequentially arranged electrodes, a perforated iron anode, a porous copper cathode followed by a mesh-type mixed metal oxide anode. The iron anode generates ferrous species and a chemically reducing environment, the porous cathode provides a reactive electrochemically reducing barrier, and the inert anode provides protons and oxygen to neutralize the system. The redox conditions of the electrolyte flowing through this system can be regulated by controlling the distribution of the electric current. Column experiments are conducted to evaluate the process and study the variables. The electrochemical reduction on a copper foam cathode produced an electrode-based reductive potential capable of reducing TCE and nitrate. Rational electrodes arrangement, longer residence time of electrolytes and higher surface area of the foam electrode improve the reductive transformation of TCE. More than 82.2% TCE removal efficiency is achieved for the case of low influent concentration (<7.5 mg/L) and high current (>45 mA). The ferrous species produced from the iron anode not only enhance the transformation of TCE on the cathode, but also facilitates transformation of other contaminants including dichromate, selenate and arsenite. Removal efficiencies greater than 80% are achieved for these contaminants in flowing contaminated water. The overall system, comprising the electrode-based and electrolyte-based barriers, can be engineered as a versatile and integrated remedial method for a relatively wide spectrum of contaminants and their mixtures.

PCE DNAPL degradation using ferrous iron solid mixture (ISM).

PubMed

Lee, Hong-Kyun; Do, Si-Hyun; Batchelor, Bill; Jo, Young-Hoon; Kong, Sung-Ho

2009-08-01

Ferrous iron solid mixture (ISM) containing Fe(II), Fe(III), and Cl was synthesized for degradation of tetrachloroethene (PCE) as a dense non-aqueous phase liquid (DNAPL), and an extraction procedure was developed to measure concentrations of PCE in both the aqueous and non-aqueous phases. This procedure included adding methanol along with hexane in order to achieve the high extraction efficiency, particularly when solids were present. When PCE was present as DNAPL, dechlorination of PCE was observed to decrease linearly with respect to the total PCE concentration (aqueous and non-aqueous phases) and the concentration of PCE in the aqueous phase was observed to be approximately constant. In the absence of DNAPL, the rate of PCE degradation was observed to be the first-order with respect to the concentration in the aqueous phase. A kinetic model was developed to describe these observations and it was able to fit experimental data well. Increasing the concentration of Fe(II) in ISM increased the values of rate constants, while increasing the concentration of PCE DNAPL did not affect the value of the rate constant. The reactivity of ISM for PCE dechlorination might be close to that of Friedel's salt, and the accumulation of trichloroethylene (TCE) might imply the lower reactivity of ISM for degradation of TCE or the necessity of large amount of Fe(II) in ISM. TCE (the major chlorinated intermediate), ethene (the major non-chlorinated compound), acetylene and ethane were detected, which implied that both hydrogenolysis and beta-elimination were pathways of PCE DNAPL degradation on ISM.

Effect of emplaced nZVI mass and groundwater velocity on PCE dechlorination and hydrogen evolution in water-saturated sand.

PubMed

Kim, Hye-Jin; Leitch, Megan; Naknakorn, Bhanuphong; Tilton, Robert D; Lowry, Gregory V

2017-01-15

The effect of nZVI mass loading and groundwater velocity on the tetrachloroethylene (PCE) dechlorination rate and the hydrogen evolution rate for poly(maleic acid-co-olefin) (MW=12K) coated nZVI was examined. In batch reactors, the PCE reaction rate constant (3.7×10 -4 Lhr -1 m -2 ) and hydrogen evolution rate constant (1.4 nanomolLhr -1 m -2 ) were independent of nZVI concentration above 10g/L, but the PCE dechlorination rate decreased and the hydrogen evolution rate increased for nZVI concentration below 10g/L. The nonlinearity between nZVI mass loading and PCE dechlorination and H 2 evolution was explained by differences in pH and E h at each nZVI mass loading; PCE reactivity increased when solution E h decreased, and the H 2 evolution rate increased with decreasing pH. Thus, nZVI mass loading of <5g/L yields lower reactivity with PCE and lower efficiency of Fe° utilization than for higher nZVI mass loading. The PCE dechlorination rate increased with increasing pore-water velocity, suggesting that mass transfer limits the reaction at low porewater velocity. Overall, this work suggests that design of nZVI-based reactive barriers for groundwater treatment should consider the non-linear effects of both mass loading and flow velocity on performance and expected reactive lifetime. Copyright © 2016 Elsevier B.V. All rights reserved.

Heterogeneous carbonaceous matter in sedimentary rock lithocomponents causes significant trichloroethylene (TCE) sorption in a low organic carbon content aquifer/aquitard system.

PubMed

Choung, Sungwook; Zimmerman, Lisa R; Allen-King, Richelle M; Ligouis, Bertrand; Feenstra, Stanley

2014-10-15

This study evaluated the effects of heterogeneous thermally altered carbonaceous matter (CM) on trichloroethylene (TCE) sorption for a low fraction organic carbon content (foc) alluvial sedimentary aquifer and aquitard system (foc=0.046-0.105%). The equilibrium TCE sorption isotherms were highly nonlinear with Freundlich exponents of 0.46-0.58. Kerogen+black carbon was the dominant CM fraction extracted from the sediments and accounted for >60% and 99% of the total in the sands and silt, respectively. Organic petrological examination determined that the kerogen included abundant amorphous organic matter (bituminite), likely of marine origin. The dark calcareous siltstone exhibited the greatest TCE sorption among aquifer lithocomponents and accounted for most sorption in the aquifer. The results suggest that the source of the thermally altered CM, which causes nonlinear sorption, was derived from parent Paleozoic marine carbonate rocks that outcrop throughout much of New York State. A synthetic aquifer-aquitard unit system (10% aquitard) was used to illustrate the effect of the observed nonlinear sorption on mass storage potential at equilibrium. The calculation showed that >80% of TCE mass contained in the aquifer was sorbed on the aquifer sediment at aqueous concentration <1000 μgL(-1). These results show that sorption is likely a significant contributor to the persistence of a TCE groundwater plume in the aquifer studied. It is implied that sorption may similarly contribute to TCE persistence in other glacial alluvial aquifers with similar geologic characteristics, i.e., comprised of sedimentary rock lithocomponents that contain thermally altered CM. Copyright © 2014 Elsevier B.V. All rights reserved.

Heterogeneous carbonaceous matter in sedimentary rock lithocomponents causes significant trichloroethylene (TCE) sorption in a low organic carbon content aquifer/aquitard system

NASA Astrophysics Data System (ADS)

Choung, Sungwook; Zimmerman, Lisa R.; Allen-King, Richelle M.; Ligouis, Bertrand; Feenstra, Stanley

2014-10-01

This study evaluated the effects of heterogeneous thermally altered carbonaceous matter (CM) on trichloroethylene (TCE) sorption for a low fraction organic carbon content (foc) alluvial sedimentary aquifer and aquitard system (foc = 0.046-0.105%). The equilibrium TCE sorption isotherms were highly nonlinear with Freundlich exponents of 0.46-0.58. Kerogen + black carbon was the dominant CM fraction extracted from the sediments and accounted for > 60% and 99% of the total in the sands and silt, respectively. Organic petrological examination determined that the kerogen included abundant amorphous organic matter (bituminite), likely of marine origin. The dark calcareous siltstone exhibited the greatest TCE sorption among aquifer lithocomponents and accounted for most sorption in the aquifer. The results suggest that the source of the thermally altered CM, which causes nonlinear sorption, was derived from parent Paleozoic marine carbonate rocks that outcrop throughout much of New York State. A synthetic aquifer-aquitard unit system (10% aquitard) was used to illustrate the effect of the observed nonlinear sorption on mass storage potential at equilibrium. The calculation showed that > 80% of TCE mass contained in the aquifer was sorbed on the aquifer sediment at aqueous concentration < 1000 μg L- 1. These results show that sorption is likely a significant contributor to the persistence of a TCE groundwater plume in the aquifer studied. It is implied that sorption may similarly contribute to TCE persistence in other glacial alluvial aquifers with similar geologic characteristics, i.e., comprised of sedimentary rock lithocomponents that contain thermally altered CM.

Summary of External Peer Review and Public Comments and Disposition for Trichloroethylene (TCE)

EPA Pesticide Factsheets

This document summarizes the public and external peer review comments that the EPA’s Office of Pollution Prevention and Toxics (OPPT) received for the draft work plan risk assessment for trichloroethylene (TCE).

Monitoring trichloroethene remediation at an iron permeable reactive barrier using stable carbon isotopic analysis

NASA Astrophysics Data System (ADS)

VanStone, Nancy; Przepiora, Andrzej; Vogan, John; Lacrampe-Couloume, Georges; Powers, Brian; Perez, Ernesto; Mabury, Scott; Sherwood Lollar, Barbara

2005-08-01

Stable carbon isotopic analysis, in combination with compositional analysis, was used to evaluate the performance of an iron permeable reactive barrier (PRB) for the remediation of ground water contaminated with trichloroethene (TCE) at Spill Site 7 (SS7), F.E. Warren Air Force Base, Wyoming. Compositional data indicated that although the PRB appeared to be reducing TCE to concentrations below treatment goals within and immediately downgradient of the PRB, concentrations remained higher than expected at wells further downgradient (i.e. > 9 m) of the PRB. At two wells downgradient of the PRB, TCE concentrations were comparable to upgradient values, and δ13C values of TCE at these wells were not significantly different than upgradient values. Since the process of sorption/desorption does not significantly fractionate carbon isotope values, this suggests that the TCE observed at these wells is desorbing from local aquifer materials and was present before the PRB was installed. In contrast, three other downgradient wells show significantly more enriched δ13C values compared to the upgradient mean. In addition, δ13C values for the degradation products of TCE, cis-dichloroethene and vinyl chloride, show fractionation patterns expected for the products of the reductive dechlorination of TCE. Since concentrations of both TCE and degradation products drop to below detection limit in wells within the PRB and directly below it, these downgradient chlorinated hydrocarbon concentrations are attributed to desorption from local aquifer material. The carbon isotope values indicate that this dissolved contaminant is subject to local degradation, likely due to in situ microbial activity.

Monitoring trichloroethene remediation at an iron permeable reactive barrier using stable carbon isotopic analysis.

PubMed

VanStone, Nancy; Przepiora, Andrzej; Vogan, John; Lacrampe-Couloume, Georges; Powers, Brian; Perez, Ernesto; Mabury, Scott; Sherwood Lollar, Barbara

2005-08-01

Stable carbon isotopic analysis, in combination with compositional analysis, was used to evaluate the performance of an iron permeable reactive barrier (PRB) for the remediation of ground water contaminated with trichloroethene (TCE) at Spill Site 7 (SS7), F.E. Warren Air Force Base, Wyoming. Compositional data indicated that although the PRB appeared to be reducing TCE to concentrations below treatment goals within and immediately downgradient of the PRB, concentrations remained higher than expected at wells further downgradient (i.e. >9 m) of the PRB. At two wells downgradient of the PRB, TCE concentrations were comparable to upgradient values, and delta13C values of TCE at these wells were not significantly different than upgradient values. Since the process of sorption/desorption does not significantly fractionate carbon isotope values, this suggests that the TCE observed at these wells is desorbing from local aquifer materials and was present before the PRB was installed. In contrast, three other downgradient wells show significantly more enriched delta13C values compared to the upgradient mean. In addition, delta13C values for the degradation products of TCE, cis-dichloroethene and vinyl chloride, show fractionation patterns expected for the products of the reductive dechlorination of TCE. Since concentrations of both TCE and degradation products drop to below detection limit in wells within the PRB and directly below it, these downgradient chlorinated hydrocarbon concentrations are attributed to desorption from local aquifer material. The carbon isotope values indicate that this dissolved contaminant is subject to local degradation, likely due to in situ microbial activity.

Electrolytic Manipulation of Persulfate Reactivity by Iron Electrodes for TCE Degradation in Groundwater

PubMed Central

Yuan, Songhu; Liao, Peng; Alshawabkeh, Akram N.

2014-01-01

Activated persulfate oxidation is an effective in situ chemical oxidation process for groundwater remediation. However, reactivity of persulfate is difficult to manipulate or control in the subsurface causing activation before reaching the contaminated zone and leading to a loss of chemicals. Furthermore, mobilization of heavy metals by the process is a potential risk. An effective approach using iron electrodes is thus developed to manipulate the reactivity of persulfate in situ for trichloroethylene (TCE) degradation in groundwater, and to limit heavy metals mobilization. TCE degradation is quantitatively accelerated or inhibited by adjusting the current applied to the iron electrode, following k1 = 0.00053•Iv + 0.059 (−122 A/m3 ≤ Iv ≤ 244 A/m3) where k1 and Iv are the pseudo first-order rate constant (min−1) and volume normalized current (A/m3), respectively. Persulfate is mainly decomposed by Fe2+ produced from the electrochemical and chemical corrosion of iron followed by the regeneration via Fe3+ reduction on the cathode. SO4•− and •OH co-contribute to TCE degradation, but •OH contribution is more significant. Groundwater pH and oxidation-reduction potential can be restored to natural levels by the continuation of electrolysis after the disappearance of contaminants and persulfate, thus decreasing adverse impacts such as the mobility of heavy metals in the subsurface. PMID:24328192

Inhibition of Adrenergic and Non-Adrenergic Smooth Muscle Contraction in the Human Prostate by the Phosphodiesterase 10-Selective Inhibitor TC-E 5005.

PubMed

Hennenberg, Martin; Schott, Melanie; Kan, Aysenur; Keller, Patrick; Tamalunas, Alexander; Ciotkowska, Anna; Rutz, Beata; Wang, Yiming; Strittmatter, Frank; Herlemann, Annika; Yu, Qingfeng; Stief, Christian G; Gratzke, Christian

2016-11-01

The phosphodiesterase (PDE) 5 inhibitor tadalafil is available for treatment of male lower urinary tract symptoms (LUTS), while the role of other PDE isoforms for prostate smooth muscle tone is still unknown. Here, we examined effects of the PDE10-selective inhibitor TC-E 5005 on smooth muscle contraction in human prostate tissue. Prostate samples were obtained from patients undergoing radical prostatectomy. Expression of PDE10 was addressed by RT-PCR, Western blot, and fluorescence staining with different markers. Effects of TC-E 5005 and tadalafil on contraction, and relaxation of prostate strips were studied via organ bath. PDE10A was detectable by RT-PCR, Western blot, and fluorescence staining in prostate tissues. Colocalization with markers suggested expression of PDE10A in smooth muscle cells and catecholaminergic nerves. Norepinephrine, the α1 -adrenergic agonist phenylephrine, the thromboxane A2 analogue U46619, and endothelins 1-3 induced concentration-dependent contractions of prostate strips, while electric field stimulation (EFS) induced frequence-dependent contractions. Application of TC-E 5005 (500 nM) caused significant inhibition of norepinephrine-, phenylephrine-, and endothelin-3-induced contractions. Inhibition of EFS-induced contractions by TC-E 5005 ranged around 50%, resembling inhibition of EFS-induced contractions by tadalafil (10 μM). The prostacyclin analog treprostinil and the nitric oxide donor DEA NONOate induced relaxations of precontracted prostate strips, which were significantly amplified by TCE 5005. The PDE10-selective inhibitor TC-E 5005 inhibits adrenergic and neurogenic smooth muscle contractions in the human prostate. TC-E 5005 inhibits neurogenic contractions with similar efficacy than tadalafil, so that urodynamic effects in vivo appear possible. Prostate 76:1364-1374, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Time-dependent bacterial community and electrochemical characterizations of cathodic biofilms in the surfactant-amended sediment-based bioelectrochemical reactor with enhanced 2,3,4,5-tetrachlorobiphenyl dechlorination.

PubMed

Wan, Hui; Yi, Xiaoyun; Liu, Xiaoping; Feng, Chunhua; Dang, Zhi; Wei, Chaohai

2018-05-01

Applying an electric field to stimulate the microbial reductive dechlorination of polychlorinated biphenyls (PCBs) represents a promising approach for bioremediation of PCB-contaminated sites. This study aimed to demonstrate the biocathodic film-facilitated reduction of PCB 61 in a sediment-based bioelectrochemical reactor (BER) and, more importantly, the characterizations of electrode-microbe interaction from microbial and electrochemical perspectives particularly in a time-dependent manner. The application of a cathodic potential (-0.45 V vs. SHE) significantly improved the rate and extent of PCB 61 dechlorination compared to the open-circuit scenario (without electrical stimulation), and the addition of an external surfactant further increased the dechlorination, with Tween 80 exerting more pronounced effects than rhamnolipid. The bacterial composition of the biofilms and the bioelectrochemical kinetics of the BERs were found to be time-dependent and to vary considerably with the incubation time and slightly with the coexistence of an external surfactant. Excellent correlations were observed between the dechlorination rate and the relative abundance of Dehalogenimonas, Dechloromonas, and Geobacter, the dechlorination rate and the cathodic current density recorded from the chronoamperometry tests, and the dechlorination rate and the charge transfer resistance derived from the electrochemical impedance tests, with respect to the 120 day-operation. After day 120, PCB 61 was resistant to further appreciable reduction, but substantial hydrogen production was detected, and the bacterial community and electrochemical parameters observed on day 180 were not distinctly different from those on day 120. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dechlorination Kinetics Of Monochlorobiphenyls By Fe/Pd: Effects Of Solvent, Temperature, And PCB Concentration

EPA Science Inventory

Well-known, yet undefined, changes in the conditions and activity of palladized zerovalent iron (Fe/Pd) over an extended period of time hindered a careful study of dechlorination kinetics in long-term experiments. A short-term experimental method was, therefore, developed to stud...

Analysis of TCE Fate and Transport in Karst Groundwater Systems Using Statistical Mixed Models

NASA Astrophysics Data System (ADS)

Anaya, A. A.; Padilla, I. Y.

2012-12-01

Karst groundwater systems are highly productive and provide an important fresh water resource for human development and ecological integrity. Their high productivity is often associated with conduit flow and high matrix permeability. The same characteristics that make these aquifers productive also make them highly vulnerable to contamination and a likely for contaminant exposure. Of particular interest are trichloroethylene, (TCE) and Di-(2-Ethylhexyl) phthalate (DEHP). These chemicals have been identified as potential precursors of pre-term birth, a leading cause of neonatal complications with a significant health and societal cost. Both of these contaminants have been found in the karst groundwater formations in this area of the island. The general objectives of this work are to: (1) develop fundamental knowledge and determine the processes controlling the release, mobility, persistence, and possible pathways of contaminants in karst groundwater systems, and (2) characterize transport processes in conduit and diffusion-dominated flow under base flow and storm flow conditions. The work presented herein focuses on the use of geo-hydro statistical tools to characterize flow and transport processes under different flow regimes, and their application in the analysis of fate and transport of TCE. Multidimensional, laboratory-scale Geo-Hydrobed models (GHM) were used for this purpose. The models consist of stainless-steel tanks containing karstified limestone blocks collected from the karst aquifer formation of northern Puerto Rico. The models integrates a network of sampling wells to monitor flow, pressure, and solute concentrations temporally and spatially. Experimental work entails injecting dissolved CaCl2 tracers and TCE in the upstream boundary of the GHM while monitoring TCE and tracer concentrations spatially and temporally in the limestone under different groundwater flow regimes. Analysis of the temporal and spatial concentration distributions of solutes

DETERMINATION OF RATES AND EXTENT OF DECHLORINATION IN PCB-CONTAMINATED SEDIMENTS DURING MONITORED NATURAL RECOVERY

EPA Science Inventory

This "Sediment Issue" summarizes investigations carried out by the National Risk Management Research Laboratory (NRMRL) of U.S. EPA to evaluate the long-term recovery of polychlorinated biphenyl (PCB)-contaminated sediments via reductive dechlorination. The magnitude, extent, an...

COMPLETE NATURAL ATTENUATION OF A PCE AND TCE PLUME AFTER SOURCE REMOVAL

EPA Science Inventory

Disposal of the chlorinated solvents PCE and TCE at the Twin Cities Army Ammunition Plant (TCAAP) resulted in the contamination of groundwater in a shallow, unconsolidated sand aquifer. The resulting plume had moved over 1000 feet from the disposal source area and had impacted p...

Identification of TCE and PCE sorption and biodegradation parameters in a sandy aquifer for fate and transport modelling: batch and column studies.

PubMed

Kret, E; Kiecak, A; Malina, G; Nijenhuis, I; Postawa, A

2015-07-01

The main aim of this study was to determine the sorption and biodegradation parameters of trichloroethene (TCE) and tetrachloroethene (PCE) as input data required for their fate and transport modelling in a Quaternary sandy aquifer. Sorption was determined based on batch and column experiments, while biodegradation was investigated using the compound-specific isotope analysis (CSIA). The aquifer materials medium (soil 1) to fine (soil 2) sands and groundwater samples came from the representative profile of the contaminated site (south-east Poland). The sorption isotherms were approximately linear (TCE, soil 1, K d = 0.0016; PCE, soil 1, K d = 0.0051; PCE, soil 2, K d = 0.0069) except for one case in which the best fitting was for the Langmuir isotherm (TCE, soil 2, K f = 0.6493 and S max = 0.0145). The results indicate low retardation coefficients (R) of TCE and PCE; however, somewhat lower values were obtained in batch compared to column experiments. In the column experiments with the presence of both contaminants, TCE influenced sorption of PCE, so that the R values for both compounds were almost two times higher. Non-significant differences in isotope compositions of TCE and PCE measured in the observation points (δ(13)C values within the range of -23.6 ÷ -24.3‰ and -26.3 ÷-27.7‰, respectively) indicate that biodegradation apparently is not an important process contributing to the natural attenuation of these contaminants in the studied sandy aquifer.

Numerical simulations of the impact of seasonal heat storage on source zone emission in a TCE contaminated aquifer

NASA Astrophysics Data System (ADS)

Popp, Steffi; Beyer, Christof; Dahmke, Andreas; Bauer, Sebastian

2016-04-01

In urban regions, with high population densities and heat demand, seasonal high temperature heat storage in the shallow subsurface represents an attractive and efficient option for a sustainable heat supply. In fact, the major fraction of energy consumed in German households is used for room heating and hot water production. Especially in urbanized areas, however, the installation of high temperature heat storage systems is currently restricted due to concerns on negative influences on groundwater quality caused e.g. by possible interactions between heat storages and subsurface contaminants, which are a common problem in the urban subsurface. Detailed studies on the overall impact of the operation of high temperature heat storages on groundwater quality are scarce. Therefore, this work investigates possible interactions between groundwater temperature changes induced by heat storage via borehole heat exchangers and subsurface contaminations by numerical scenario analysis. For the simulation of non-isothermal groundwater flow, and reactive transport processes the OpenGeoSys code is used. A 2D horizontal cross section of a shallow groundwater aquifer is assumed in the simulated scenario, consisting of a sandy sediment typical for Northern Germany. Within the aquifer a residual trichloroethene (TCE) contaminant source zone is present. Temperature changes are induced by a seasonal heat storage placed within the aquifer with scenarios of maximum temperatures of 20°C, 40°C and 60°C, respectively, during heat injection and minimum temperatures of 2°C during heat extraction. In the scenario analysis also the location of the heat storage relative to the TCE source zone and plume was modified. Simulations were performed in a homogeneous aquifer as well as in a set of heterogeneous aquifers with hydraulic conductivity as spatially correlated random fields. In both cases, results show that the temperature increase in the heat plume and the consequential reduction of water

Dechlorination by ultraviolet radiation: a suitable alternative to activated carbon in dialysis water systems?

PubMed

James, Ray

2009-12-01

Chlorine-based products are widely used in the water supply industry, and the potential for adverse effects in the haemodialysis setting is well documented. To date, the most commonly used method of chlorine removal has been granular activated carbon filters. An increasingly popular method of dechlorination is the use of high intensity, broad-spectrum UV systems to reduce both free chlorine and combined chlorine compounds (chloramines) into easily removed by-products. UV radiation has been successfully used in the pharmaceutical and food industries to destroy free chlorine and/or chloramines present in water, and kill all known spoilage microorganisms including bacteria, viruses, yeasts and moulds (and their spores). This nonchemical method can offer significant advantages and benefits compared to conventional dechlorination technologies currently employed in dialysis water systems. Whilst UV treatment at 254 nm wavelength has been routinely used for disinfection purposes in dialysis water systems, this paper considers whether UV radiation can be used as an alternative to more traditional methods of chlorine removal.

UNCERTAINTY ANALYSIS OF TCE USING THE DOSE EXPOSURE ESTIMATING MODEL (DEEM) IN ACSL

EPA Science Inventory

The ACSL-based Dose Exposure Estimating Model(DEEM) under development by EPA is used to perform art uncertainty analysis of a physiologically based pharmacokinetic (PSPK) model of trichloroethylene (TCE). This model involves several circulating metabolites such as trichloroacet...

Resilience and recovery of Dehalococcoides mccartyi following low pH exposure.

PubMed

Yang, Yi; Cápiro, Natalie L; Yan, Jun; Marcet, Tyler F; Pennell, Kurt D; Löffler, Frank E

2017-12-01

Bioremediation treatment (e.g. biostimulation) can decrease groundwater pH with consequences for Dehalococcoides mccartyi (Dhc) reductive dechlorination activity. To explore the pH resilience of Dhc, the Dhc-containing consortium BDI was exposed to pH 5.5 for up to 40 days. Following 8- and 16-day exposure periods to pH 5.5, dechlorination activity and growth recovered when returned to pH 7.2; however, the ability of the culture to dechlorinate vinyl chloride (VC) to ethene was impaired (i.e. decreased rate of VC transformation). Dhc cells exposed to pH 5.5 for 40 days did not recover the ethene-producing phenotype upon transfer to pH 7.2 even after 200 days of incubation. When returned to pH 7.2 conditions after an 8-, a 16- and a 40-day low pH exposure, tceA and vcrA genes showed distinct fold increases, suggesting Dhc strain-specific responses to low pH exposure. Furthermore, a survey of Dhc biomarker genes in groundwater samples revealed the average abundances of Dhc 16S rRNA, tceA and vcrA genes in pH 4.5-6 groundwater were significantly lower (P-value < 0.05) than in pH 6-8.3 groundwater. Overall, the results of the laboratory study and the assessment of field data demonstrate that sustained Dhc activity should not be expected in low pH groundwater, and the duration of low pH exposure affects the ability of Dhc to recover activity at circumneutral pH. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Perfluoroalkyl Acids Shift Microbial Community Structure Across Experimental Scales

NASA Astrophysics Data System (ADS)

Weathers, T. S.; Sharp, J.

2016-12-01

Perfluoroalkyl acids (PFAAs) are contaminants of emerging concern that have increasingly been found in groundwater and drinking water systems. Previously, we demonstrated that PFAAs significantly alter the abundance of specific microbial clades in batch reductive dechlorinating systems, resulting in decreased chlorinated solvent attenuation capabilities. To further understand the impacts of PFAA exposure on subsurface microbial processes and PFAA transport, we investigated changes in microbial community structure as a function of PFAA presence in flow-through columns simulating aquifer transport. Phylogenetic analysis using high throughput, next generation sequencing performed after exposure to 250 pore volumes of source zone concentrations of PFAAs (10 mg/L each of 11 analytes including PFOS and PFOA) resulted in patterns that mirrored those observed in batch systems, demonstrating a conservation of community dynamics across experimental scales. Of the nine clades observed in both batch and flow-through systems, six were similarly impacted as a function of PFAA exposure, regardless of the experimental differences in transport and redox state. Specifically, the presence of PFAAs enhanced the relative abundance of Archaea, Bacteroidetes (phylum), and the family Veillonellaceae in both systems. Repressed clades include the genus Sedimentibacter, Ruminococcaceae (family), and the Anaerolineales, which contains Dehalococcoides, a genus known for its ability to fully dechlorinate TCE. As PFAAs are often co-located with TCE and BTEX, changes in microbial community structure can result in hindered bioremediation of these co-contaminants. Consideration of community shifts and corresponding changes in behavior, such as repressed reductive dechlorination or increased biofilm formation, will aid in the development of conceptual site models that account for co-contaminant bioremediation potential and PFAA transport.

In situ detection of organic molecules: Optrodes for TCE (trichloroethylene) and CHCl sub 3

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

Angel, S. M.; Langry, K. C.; Ridley, M. N.

1990-05-01

We have developed new absorption-based chemical indicators for detecting chloroform (CHCl{sub 3}) and trichloroethylene (TCE). These indicators were used to make very sensitive optical chemical sensors (optrodes) for each of these two contaminants. Concentrations below 10 ppb can be accurately measured using these sensors. Furthermore, they are selective and do not response to similar contaminants commonly found with TCE and CHCl{sub 3} in contaminated groundwater. In addition, the sensor response is linearly proportional to the chemical concentration. In this report, we describe the details of this optrode and the putative reaction sequences of the indicator chemistries with CHCl{sub 3} andmore » TCE and present an analysis of the spectral data obtained from the reaction products. A key part of the development of this optrode was designing a simple readout device. The readout is a dual-channel fiber-optic fluorimeter modified to measure transmission or absorption of light. The system is controlled by a lap-top microcomputer and is fully field portable. In addition to describing the final absorption optrode, details of the chemical indicator reactions are presented for both absorption- (colorimetric) and fluorescence-based optrodes. Finally, we report on the syntheses of several compounds used to evaluate the indicator chemical reactions that led to the development of the absorption optrode. 23 refs., 26 figs., 1 tab.« less

Potential for Methanotroph-Mediated Natural Attenuation of TCE in a Basalt Aquifer

NASA Astrophysics Data System (ADS)

Colwell, F. S.; Newby, D. T.; Reed, D. W.; Igoe, A.; Petzke, L.; Delwiche, M. E.; McKinley, J. P.; Roberto, F. F.; Whiticar, M. J.

2002-12-01

Methanotrophic bacteria are one of the microbial communities believed to be responsible for natural attenuation of a trichloroethylene (TCE) plume in the Snake River Plain Aquifer (SRPA). To better understand the role that indigenous methanotrophs may have in TCE degradation in the aquifer, groundwater was collected from four SRPA wells and analyzed for geochemical properties and methanotroph diversity. Dissolved methane concentrations in the aquifer ranged from 1 to >1000 nM. Stable carbon isotope ratios for dissolved methane suggest a microbial source for the methane (del 13C values of ca. -61 per mil in three wells). The combination of 13C enriched methane and 13C depleted-dissolved inorganic carbon in one of the wells suggests that microbial oxidation of methane occurs. Filtered groundwater yielded microorganisms that were used as inocula for enrichments or were frozen and subsequently extracted for DNA. Primers that target taxonomic (type I and type II 16S rDNA) or functional (mmoX and pmoA methane monooxygenase subunits) genes were used to characterize the indigenous methanotrophs via PCR, cloning, and sequencing. DNA sequencing and alignment results suggest that clones with sequences most similar to Methylocystis sp. (a type II methanotroph) and Methylobacter sp. (a type I methanotroph) are frequently present in filtered groundwater with the former often represented in enrichment cultures as well. Methanotroph genes are detected in the aquifer even in wells having methane concentrations as low as 1 nM. Methanotroph presence and a microbial origin for the dissolved methane indicate that microbial cycling of this key gas may play a role in the destruction of TCE in the aquifer.

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

NASA Astrophysics Data System (ADS)

Suchomel, Eric J.; Ramsburg, C. Andrew; Pennell, Kurt D.

2007-12-01

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween® 80) and sodium dihexyl sulfosuccinate (Aerosol® MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl 2 yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (> 30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR = 1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (< 5%) occurring when the total trapping number exceeded 2 × 10 - 5 . These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple

RATE OF TCE DEGRADATION IN A PLANT MULCH PASSIVE REACTIVE BARRIER (BIOWALL)

EPA Science Inventory

A passive reactive barrier was installed at the OU-1 site at Altus Air Force Base, Oklahoma to treat TCE contamination in ground water from a landfill. Depth to ground water varies from 1.8 to 2.4 meters below land surface. To intercept and treat the plume of contaminated groun...

Sustainable remediation: electrochemically assisted microbial dechlorination of tetrachloroethene-contaminated groundwater.

PubMed

Patil, Sayali S; Adetutu, Eric M; Rochow, Jacqueline; Mitchell, James G; Ball, Andrew S

2014-01-01

Microbial electric systems (MESs) hold significant promise for the sustainable remediation of chlorinated solvents such as tetrachlorethene (perchloroethylene, PCE). Although the bio-electrochemical potential of some specific bacterial species such as Dehalcoccoides and Geobacteraceae have been exploited, this ability in other undefined microorganisms has not been extensively assessed. Hence, the focus of this study was to investigate indigenous and potentially bio-electrochemically active microorganisms in PCE-contaminated groundwater. Lab-scale MESs were fed with acetate and carbon electrode/PCE as electron donors and acceptors, respectively, under biostimulation (BS) and BS-bioaugmentation (BS-BA) regimes. Molecular analysis of the indigenous groundwater community identified mainly Spirochaetes, Firmicutes, Bacteroidetes, and γ and δ-Proteobacteria. Environmental scanning electron photomicrographs of the anode surfaces showed extensive indigenous microbial colonization under both regimes. This colonization and BS resulted in 100% dechlorination in both treatments with complete dechlorination occurring 4 weeks earlier in BS-BA samples and up to 11.5 μA of current being generated. The indigenous non-Dehalococcoides community was found to contribute significantly to electron transfer with ∼61% of the current generated due to their activities. This study therefore shows the potential of the indigenous non-Dehalococcoides bacterial community in bio-electrochemically reducing PCE that could prove to be a cost-effective and sustainable bioremediation practice. © 2013 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Impact Of Organic Solvents And Common Anions On 2-Chlorobiphenyl Dechlorination Kinetics With Pd/Mg

EPA Science Inventory

The current study evaluates Pd/Mg performance for 2-chlorobiphenyl (2-CB) dechlorination in the presence of naturally abundant anions such as sulfate, chloride, nitrate, hydroxide and carbonates and organic solvents that are used for ex-situ PCB extraction or may accompany PCB co...

Degradation of Perchloroethene by zero-valent iron evaluated by carbon isotope fractionation

NASA Astrophysics Data System (ADS)

Leitner, Simon; Watzinger, Andrea; Reichenauer, Thomas G.

2014-05-01

Perchloroethene (PCE) is a widely spread groundwater contaminant in formally used industrial sites. Zero valent iron (ZVI) is used for in situ chemical reduction (ISCR) of PCE contaminants in the groundwater. A key factor in the application of in situ remediation technologies is a proper monitoring of contaminant reduction. The measurement of the stable isotope ratio is a promising method that is already used for quantifying microbial degradation of chlorinated contaminants. The carbon isotope ratio of PCE, measured by - isotope ratio mass spectrometry coupled to a gas chromatograph via a combustion interface (GC-C-IRMS), increases during degradation of PCE and can be directly related to the degree of degradation. It can be used to directly quantify chemical degradation and thus serves as a useful monitoring tool for groundwater remediation. An experiment to determine the carbon isotopic fractionation factor was performed as a lab experiment using Nanofer Star (NANOIRON). Two different PCE concentrations (c1: 220mgL-1, c2: 110mgL-1) mixed with 0.5 g of ZVI were sealed under deoxygenated conditions in 250 ml glas bottles locked with mininert caps. The bottles were incubated on a shaker for 865 h. Samples were taken weekly to measure the change in the carbon isotopic ratio of PCE as well as its concentration. Results showed a strong increase in the carbon isotope ratio (δ-value) of PCE (start: -27 o end: -4 ), which indicates a significant dechlorination process of PCE. Beside PCE also one degradation product (Trichloroethylene - TCE) was measured. TCE was further dechlorinated as indicated by the δ-value change of TCE from -26 o to -4 oȦn unexpected intermediate value of -45 o for TCE was observed in the experiment. This fluctuation could be induced by the time depending concentration due to degradation and conversation processes. Furthermore, it seems that the progress of the δ-value is affected by the starting concentration of PCE (δ-value of c1 < c2) as

The influence of in situ chemical oxidation on microbial community composition in groundwater contaminated with chlorinated solvents.

PubMed

Sercu, Bram; Jones, Antony D G; Wu, Cindy H; Escobar, Mauricio H; Serlin, Carol L; Knapp, Timothy A; Andersen, Gary L; Holden, Patricia A

2013-01-01

In situ chemical oxidation with permanganate has become an accepted remedial treatment for groundwater contaminated with chlorinated solvents. This study focuses on the immediate and short-term effects of sodium permanganate (NaMnO(4)) on the indigenous subsurface microbial community composition in groundwater impacted by trichloroethylene (TCE). Planktonic and biofilm microbial communities were studied using groundwater grab samples and reticulated vitreous carbon passive samplers, respectively. Microbial community composition was analyzed by terminal restriction fragment length polymorphism and a high-density phylogenetic microarray (PhyloChip). Significant reductions in microbial diversity and biomass were shown during NaMnO(4) exposure, followed by recovery within several weeks after the oxidant concentrations decreased to <1 mg/L. Bray-Curtis similarities and nonmetric multidimensional scaling showed that microbial community composition before and after NaMnO(4) was similar, when taking into account the natural variation of the microbial communities. Also, 16S rRNA genes of two reductive dechlorinators (Desulfuromonas spp. and Sulfurospirillum spp.) and diverse taxa capable of cometabolic TCE oxidation were detected in similar quantities by PhyloChip across all monitoring wells, irrespective of NaMnO(4) exposure and TCE concentrations. However, minimal biodegradation of TCE was observed in this study, based on oxidized conditions, concentration patterns of chlorinated and nonchlorinated hydrocarbons, geochemistry, and spatiotemporal distribution of TCE-degrading bacteria.

DEPENDENCE OF A HIGH-RATE, PCE-DECHLORINATING ENRICHMENT CULTURE ON METHANOGENIC ACTIVITY. (R825549C053)

EPA Science Inventory

The role served by the presence of methanogenic activity within a tetrachloroethene (PCE)-dechlorinating culture was investigated through a series of supplementation experiments. An acclimated lactate-enrichment culture (LEC 1) capable of rapidly converting PCE to ethene was s...

EFFECTS OF THREE CONCENTRATIONS OF MIXED FATTY ACIDS ON DECHLORINATION OF TETRACHLOROETHENE IN AQUIFER MICRO- COSMS

EPA Science Inventory

Chloroethenes are among the most common organic contaminants of ground water. The biotransformation of these compounds by reductive dechlorination is a promising technology for in situ treatment. The effects of three concentrations of a fatty acids mixture on the reductive dehalo...

A Functional Genomic Approach to Chlorinated Ethenes Bioremediation

NASA Astrophysics Data System (ADS)

Lee, P. K.; Brodie, E. L.; MacBeth, T. W.; Deeb, R. A.; Sorenson, K. S.; Andersen, G. L.; Alvarez-Cohen, L.

2007-12-01

With the recent advances in genomic sciences, a knowledge-based approach can now be taken to optimize the bioremediation of trichloroethene (TCE). During the bioremediation of a heterogeneous subsurface, it is vital to identify and quantify the functionally important microorganisms present, characterize the microbial community and measure their physiological activity. In our field experiments, quantitative PCR (qPCR) was coupled with reverse-transcription (RT) to analyze both copy numbers and transcripts expressed by the 16S rRNA gene and three reductive dehalogenase (RDase) genes as biomarkers of Dehalococcoides spp. in the groundwater of a TCE-DNAPL site at Ft. Lewis (WA) that was serially subjected to biostimulation and bioaugmentation. Genes in the Dehalococcoides genus were targeted as they are the only known organisms that can completely dechlorinate TCE to the innocuous product ethene. Biomarker quantification revealed an overall increase of more than three orders of magnitude in the total Dehalococcoides population and quantification of the more liable and stringently regulated mRNAs confirmed that Dehalococcoides spp. were active. Parallel with our field experiments, laboratory studies were conducted to explore the physiology of Dehalococcoides isolates in order to develop relevant biomarkers that are indicative of the metabolic state of cells. Recently, we verified the function of the nitrogenase operon in Dehalococcoides sp. strain 195 and nitrogenase-encoding genes are ideal biomarker targets to assess cellular nitrogen requirement. To characterize the microbial community, we applied a high-density phylogenetic microarray (16S PhyloChip) that simultaneous monitors over 8,700 unique taxa to track the bacterial and archaeal populations through different phases of treatment. As a measure of species richness, 1,300 to 1,520 taxa were detected in groundwater samples extracted during different stages of treatment as well as in the bioaugmentation culture. We

Biological reduction of chlorinated solvents: Batch-scale geochemical modeling

NASA Astrophysics Data System (ADS)

Kouznetsova, Irina; Mao, Xiaomin; Robinson, Clare; Barry, D. A.; Gerhard, Jason I.; McCarty, Perry L.

2010-09-01

Simulation of biodegradation of chlorinated solvents in dense non-aqueous phase liquid (DNAPL) source zones requires a model that accounts for the complexity of processes involved and that is consistent with available laboratory studies. This paper describes such a comprehensive modeling framework that includes microbially mediated degradation processes, microbial population growth and decay, geochemical reactions, as well as interphase mass transfer processes such as DNAPL dissolution, gas formation and mineral precipitation/dissolution. All these processes can be in equilibrium or kinetically controlled. A batch modeling example was presented where the degradation of trichloroethene (TCE) and its byproducts and concomitant reactions (e.g., electron donor fermentation, sulfate reduction, pH buffering by calcite dissolution) were simulated. Local and global sensitivity analysis techniques were applied to delineate the dominant model parameters and processes. Sensitivity analysis indicated that accurate values for parameters related to dichloroethene (DCE) and vinyl chloride (VC) degradation (i.e., DCE and VC maximum utilization rates, yield due to DCE utilization, decay rate for DCE/VC dechlorinators) are important for prediction of the overall dechlorination time. These parameters influence the maximum growth rate of the DCE and VC dechlorinating microorganisms and, thus, the time required for a small initial population to reach a sufficient concentration to significantly affect the overall rate of dechlorination. Self-inhibition of chlorinated ethenes at high concentrations and natural buffering provided by the sediment were also shown to significantly influence the dechlorination time. Furthermore, the analysis indicated that the rates of the competing, nonchlorinated electron-accepting processes relative to the dechlorination kinetics also affect the overall dechlorination time. Results demonstrated that the model developed is a flexible research tool that is

Catalytic dechlorination of diclofenac by biogenic palladium in a microbial electrolysis cell

PubMed Central

Gusseme, Bart De; Soetaert, Maarten; Hennebel, Tom; Vanhaecke, Lynn; Boon, Nico; Verstraete, Willy

2012-01-01

Summary Diclofenac is one of the most commonly detected pharmaceuticals in wastewater treatment plant (WWTP) effluents and the receiving water bodies. In this study, biogenic Pd nanoparticles (‘bio‐Pd’) were successfully applied in a microbial electrolysis cell (MEC) for the catalytic reduction of diclofenac. Hydrogen gas was produced in the cathodic compartment, and consumed as a hydrogen donor by the bio‐Pd on the graphite electrodes. In this way, complete dechlorination of 1 mg diclofenac l−1 was achieved during batch recirculation experiments, whereas no significant removal was observed in the absence of the biocatalyst. The complete dechlorination of diclofenac was demonstrated by the concomitant production of 2‐anilinophenylacetate (APA). Through the addition of −0.8 V to the circuit, continuous and complete removal of diclofenac was achieved in synthetic medium at a minimal HRT of 2 h. Continuous treatment of hospital WWTP effluent containing 1.28 µg diclofenac l−1 resulted in a lower removal efficiency of 57%, which can probably be attributed to the affinity of other environmental constituents for the bio‐Pd catalyst. Nevertheless, reductive catalysis coupled to sustainable hydrogen production in a MEC offers potential to lower the release of micropollutants from point‐sources such as hospital WWTPs. PMID:22221490

Transformation impacts of dissolved and solid phase Fe(II) on trichloroethylene (TCE) reduction in an iron-reducing bacteria (IRB) mixed column system: a mathematical model.

PubMed

Bae, Yeunook; Kim, Dooil; Cho, Hyun-Hee; Singhal, Naresh; Park, Jae-Woo

2012-12-01

In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)(dissolved)) and solid form ferrous iron (Fe(II)(solid)). Results showed that TCE reduction was strongly depressed by Fe(II)(solid) rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)(solid) might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)(dissolved) was a strong contributor to TCE reduction compared to Fe(II)(solid). In addition, our research confirmed that less Fe(II)(solid) production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)(solid), Fe(II)(dissolved), Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biophysical mechanisms of trichloroethene uptake and loss in baldcypress growing in shallow contaminated groundwater

USGS Publications Warehouse

Nietch, C.T.; Morris, J.T.; Vroblesky, D.A.

1999-01-01

Wetland vegetation may be useful in the remediation of shallow contaminated aquifers. Mesocosm experiments were conducted to describe the regulatory mechanisms affecting trichloroethene (TCE) removal rates from groundwater by flood-adapted wetland trees at a contaminated site. TCE flux through baldcypress [Taxodium distichum (L) Rich] seedlings grown in glass- carboys decreased from day to night and from August to December. The diel fluctuation coincided with changes in leaf-level physiology, as the daytime flux was significantly correlated with net photosynthesis but not with respiration at night. A decrease in seedling water use from summer to winter explained the large seasonal difference in TCE flux. A simple model that simulates gas-phase diffusion through aerenchyma tested the importance of diffusion of TCE vapor from roots to the stem. The modeled diffusive flux was within 64% of the observed value during the winter but could only explain 8% of the summer flux. Seedling water use was a good estimator of flux during the summer. Hence, evapotranspiration (ET) in the summer may serve as a good predictor for the potential of TCE removal by baldcypress trees, while diffusive flux may better approximate potential contaminant loss in the winter.Wetland vegetation may be useful in the remediation of shallow contaminated aquifers. Mesocosm experiments were conducted to describe the regulatory mechanisms affecting trichloroethene (TCE) removal rates from groundwater by flood-adapted wetland trees at a contaminated site. TCE flux through baldcypress [Taxodium distichum (L) Rich] seedlings grown in glass-carboys decreased from day to night and from August to December. The diel fluctuation coincided with changes in leaf-level physiology, as the daytime flux was significantly correlated with net photosynthesis but not with respiration at night. A decrease in seedling water use from summer to winter explained the large seasonal difference in TCE flux. A simple model that

Correlation Of 2-Chlorobiphenyl Dechlorination By Fe/Pd With Iron Corrosion At Different pH

EPA Science Inventory

The rate of 2-chlorobiphenyl dechlorination by palladized iron (Fe/Pd) decreased with increasing pH until pH > 12.5. Iron corrosion potential (E_c) and current (j_c), obtained from polarization curves of a rotating disk electrode of iron, followed the Tafel e...

Combined removal of a BTEX, TCE, and cis-DCE mixture using Pseudomonas sp. immobilized on scrap tyres.

PubMed

Lu, Qihong; de Toledo, Renata Alves; Xie, Fei; Li, Junhui; Shim, Hojae

2015-09-01

The simultaneous aerobic removal of a mixture of benzene, toluene, ethylbenzene, and o,m,p-xylene (BTEX); cis-dichloroethylene (cis-DCE); and trichloroethylene (TCE) from the artificially contaminated water using an indigenous bacterial isolate identified as Pseudomonas plecoglossicida immobilized on waste scrap tyres was investigated. Suspended and immobilized conditions were compared for the removal of these volatile organic compounds. For the immobilized system, toluene, benzene, and ethylbenzene were completely removed, while the highest removal efficiencies of 99.0 ± 0.1, 96.8 ± 0.3, 73.6 ± 2.5, and 61.6 ± 0.9% were obtained for o-xylene, m,p-xylene, TCE, and cis-DCE, respectively. The sorption kinetics of contaminants towards tyre surface was also evaluated, and the sorption capacity generally followed the order of toluene > benzene > m,p-xylene > o-xylene > ethylbenzene > TCE > cis-DCE. Scrap tyres showed a good capability for the simultaneous sorption and bioremoval of BTEX/cis-DCE/TCE mixture, implying a promising waste material for the removal of contaminant mixture from industrial wastewater or contaminated groundwater.

LESSONS LEARNED FROM IN-SITU RESISTIVE HEATING OF TCE AT FORT LEWIS, WASHINGTON

EPA Science Inventory

The EGDY is the source of a potentially expanding, three mile long TCE plume in a sole source drinking water aquifer. Thermal remediation is being employed to reduce source mass loading to the dissolved phase aquifer plume and reduce the time to reach site cleanup goals. This i...

Long-term changes in ground water chemistry at a phytoremediation demonstration site

USGS Publications Warehouse

Eberts, S.M.; Jones, S.A.; Braun, C.L.; Harvey, G.J.

2005-01-01

A field-scale demonstration project was conducted to evaluate the capability of eastern cottonwood trees (Populus deltoides) to attenuate trichloroethene (TCE) contamination of ground water. By the middle of the sixth growing season, trees planted where depth to water was < 3 m delivered enough dissolved organic carbon to the underlying aquifer to lower dissolved oxygen concentrations, to create iron-reducing conditions along the plume centerline and sulfate-reducing or methanogenic conditions in localized areas, and to initiate in situ reductive dechlorination of TCE. Apparent biodegradation rate constants for TCE along the centerline of the plume beneath the phytoremediation system increased from 0.0002/d to 0.02/d during the first six growing seasons. The corresponding increase in natural attenuation capacity of the aquifer along the plume centerline, from 0.0004/m to 0.024/m, is associated with a potential decrease in plume-stabilization distance from 9680 to 160 m. Demonstration results provide insight into the amount of vegetation and time that may be needed to achieve cleanup objectives at the field scale.

ENVIROMETAL TECHNOLOGIES, INC., METAL-ENHANCED DECHLORINATION OF VOLATILE ORGANIC COMPOUNDS USING AN IN-SITU REACTIVE IRON WALL

EPA Science Inventory

This report summarizes the results of a field demonstration conducted under the SITE program. The technology that was demonstrated was a metal-enhanced dechlorination process developed by EnviroMetal Technologies, Inc. to treat groundwater contaminated with chlorinated volatile ...

Effects of dynamic redox zonation on the potential for natural attenuation of trichloroethylene at a fire-training-impacted aquifer

USGS Publications Warehouse

Skubal, K.L.; Haack, S.K.; Forney, L.J.; Adriaens, P.

1999-01-01

Hydrogeochemical and microbiological methods were used to characterize temporal changes along a transect of an aquifer contaminated by mixed hydrocarbon and solvent wastes from fire training activities at Wurtsmith Air Force Base (Oscoda, MI). Predominant terminal electron accepting processes (TEAPs) as measured by dissolved hydrogen indicated reoxygenation along the transect between October 1995 and October 1996, possibly because of recharge, fluctuations in water table elevation, or microbial activity. Microbiological analyses using universal and archaeal probes revealed a relationship between groundwater hydrogen concentration, TEAP, and predominant bacterial phylogeny. Specifically, a raised water table level and evidence of methanogenesis corresponded to an order of magnitude increase in archaeal 16S rRNA relative to when this zone was unsaturated. Spatial microbial and geochemical dynamics did not result in measurable differences in trichloroethylene (TCE) mineralization potential in vadose, capillary fringe, and saturated zone soils during a 500-day microcosm experiment using unprocessed contaminated soil and groundwater. Aerobic systems indicated that methane, but not toluene, may serve as cosubstrate for TCE cometabolism. Anaerobic microcosms demonstrated evidence for methanogenesis, CO2 production and hydrogen consumption, yet dechlorination activity was only observed in a microcosm with sulfate-reduction as the dominant TEAP. Mass balance calculations indicated less than 5% mineralization, regardless of redox zone or degree of saturation, at maximum rates of 0.01-0.03 ??mol/g soil??d. The general lack of dechlorination activity under laboratory conditions corroborates the limited evidence for natural dechlorination at this site, despite abundant electron donor material and accumulated organic acids from microbial degradation of alkylbenzenes. Thus, the short-term temporal dynamics in redox conditions is unlikely to have measurable effects on the long

MICROBIAL REDUCTIVE DECHLORINATION OF HEXACHLORO-1,3-BUTADIENE IN A METHANOGENIC ENRICHMENT CULTURE. (R825513C007)

EPA Science Inventory

Sequential reductive dechlorination of hexachloro-1,3-butadiene (HCBD) was achieved by a mixed, methanogenic culture enriched from a contaminated estuarine sediment. Both methanol and lactate served as carbon and electron sources. Methanol was stoichiometrically converted to m...

Comparative Demonstration of Active and Semi-Passive In Situ Bioremediation Approaches for Perchlorate Impacted Groundwater: Active In Situ Bioremediation Demonstration (Aerojet Facility)

DTIC Science & Technology

2012-12-01

non-pathogenic microbial consortia that are capable of mediating complete dechlorination of TCE to ethene. For example, the General Electric Company...Piezometric Surface """""" ’"’"’ 16" Normal Resistivity Log Notes: 1. Water levels w:re measured October 2001, except EW-1, EW-2, and RW- 1, wh1ch...Wells by GeoTrans or Kleinfelder. Aerojet utilized various contractors for the installation of piping and electrical controls between the wells

77 FR 20695 - Tax Counseling for the Elderly (TCE) Program Availability of Application Packages

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-05

... DEPARTMENT OF THE TREASURY Internal Revenue Service Tax Counseling for the Elderly (TCE) Program...: This document provides notice of the availability of Application Packages for the 2013 Tax Counseling... . The deadline for submitting an application package to the IRS for the Tax Counseling for the Elderly...

76 FR 30243 - Tax Counseling for the Elderly (TCE) Program Availability of Application Packages

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-24

... DEPARTMENT OF THE TREASURY Internal Revenue Service Tax Counseling for the Elderly (TCE) Program...: This document provides notice of the availability of Application Packages for the 2012 Tax Counseling.... The deadline for submitting an application package to the IRS for the 2012 Tax Counseling for the...

75 FR 22437 - Tax Counseling for the Elderly (TCE) Program Availability of Application Packages

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-28

... DEPARTMENT OF THE TREASURY Internal Revenue Service Tax Counseling for the Elderly (TCE) Program...: This document provides notice of the availability of Application Packages for the 2011 Tax Counseling.... The deadline for submitting an application package to the IRS for the 2011 Tax Counseling for the...

Estimation of rate constants of PCB dechlorination reactions using an anaerobic dehalogenation model.

PubMed

Karakas, Filiz; Imamoglu, Ipek

2017-02-15

This study aims to estimate anaerobic dechlorination rate constants (k m ) of reactions of individual PCB congeners using data from four laboratory microcosms set up using sediment from Baltimore Harbor. Pathway k m values are estimated by modifying a previously developed model as Anaerobic Dehalogenation Model (ADM) which can be applied to any halogenated hydrophobic organic (HOC). Improvements such as handling multiple dechlorination activities (DAs) and co-elution of congeners, incorporating constraints, using new goodness of fit evaluation led to an increase in accuracy, speed and flexibility of ADM. DAs published in the literature in terms of chlorine substitutions as well as specific microorganisms and their combinations are used for identification of pathways. The best fit explaining the congener pattern changes was found for pathways of Phylotype DEH10, which has the ability to remove doubly flanked chlorines in meta and para positions, para flanked chlorines in meta position. The range of estimated k m values is between 0.0001-0.133d -1 , the median of which is found to be comparable to the few available published biologically confirmed rate constants. Compound specific modelling studies such as that performed by ADM can enable monitoring and prediction of concentration changes as well as toxicity during bioremediation. Copyright © 2016 Elsevier B.V. All rights reserved.

Efficient degradation of TCE in groundwater using Pd and electro-generated H2 and O2: a shift in pathway from hydrodechlorination to oxidation in the presence of ferrous ions.

PubMed

Yuan, Songhu; Mao, Xuhui; Alshawabkeh, Akram N

2012-03-20

Degradation of trichloroethylene (TCE) in simulated groundwater by Pd and electro-generated H(2) and O(2) is investigated in the absence and presence of Fe(II). In the absence of Fe(II), hydrodechlorination dominates TCE degradation, with accumulation of H(2)O(2) up to 17 mg/L. Under weak acidity, low concentrations of oxidizing •OH radicals are detected due to decomposition of H(2)O(2), slightly contributing to TCE degradation via oxidation. In the presence of Fe(II), the degradation efficiency of TCE at 396 μM improves to 94.9% within 80 min. The product distribution proves that the degradation pathway shifts from 79% hydrodechlorination in the absence of Fe(II) to 84% •OH oxidation in the presence of Fe(II). TCE degradation follows zeroth-order kinetics with rate constants increasing from 2.0 to 4.6 μM/min with increasing initial Fe(II) concentration from 0 to 27.3 mg/L at pH 4. A good correlation between TCE degradation rate constants and •OH generation rate constants confirms that •OH is the predominant reactive species for TCE oxidation. Presence of 10 mM Na(2)SO(4), NaCl, NaNO(3), NaHCO(3), K(2)SO(4), CaSO(4), and MgSO(4) does not significantly influence degradation, but sulfite and sulfide greatly enhance and slightly suppress degradation, respectively. A novel Pd-based electrochemical process is proposed for groundwater remediation.

Efficient Degradation of TCE in Groundwater Using Pd and Electro-generated H2 and O2: A Shift in Pathway from Hydrodechlorination to Oxidation in the Presence of Ferrous Ions

PubMed Central

Yuan, Songhu; Mao, Xuhui; Alshawabkeh, Akram N.

2012-01-01

Degradation of trichloroethylene (TCE) in simulated groundwater by Pd and electro-generated H2 and O2 is investigated in the absence and presence of Fe(II). In the absence of Fe(II), hydrodechlorination dominates TCE degradation, with accumulation of H2O2 up to 17 mg/L. Under weak acidity, low concentrations of oxidizing •OH radical are detected due to decomposition of H2O2, slightly contributing to TCE degradation via oxidation. In the presence of Fe(II), the degradation efficiency of TCE at 396 μM improves to 94.9% within 80 min. The product distribution proves that the degradation pathway shifts from 79% hydrodechlorination in the absence of Fe(II) to 84% •OH oxidation in the presence of Fe(II). TCE degradation follows zeroth-order kinetics with rate constants increasing from 2.0 to 4.6 μM/min with increasing initial Fe(II) concentration from 0 to 27.3 mg/L at pH 4. A good correlation between TCE degradation rate constants and •OH generation rate constants confirms that •OH is the predominant reactive species for TCE oxidation. Presence of 10 mM Na2SO4, NaCl, NaNO3, NaHCO3, K2SO4, CaSO4 and MgSO4 does not significantly influence degradation, but sulfite and sulfide greatly enhance and slightly suppresses degradation, respectively. A novel Pd-based electrochemical process is proposed for groundwater remediation. PMID:22315993

Abiotic and Biotic Transformation of TCE under Sulfate Reducing Conditions: the Role of Spatial Heterogeneity

EPA Science Inventory

At a number of sites in the USA, passive reactive barriers built with shredded plant mulch have been constructed to treat ground water contaminated with TCE. These barriers are called biowalls because anaerobic biodegradation of the plant mulch is expected to provide substrates...

A SEARCH FOR RESIDUAL BEHAVIORAL EFFECTS OF TRICHLOROETHYLENE (TCE) IN RATS EXPOSED AS YOUNG ADULTS

EPA Science Inventory

Trichloroethylene (TCE) is a solvent of concern to the EPA due to its extensive use in industry, its prevalence in urban air, and its appearance in water supplies. Human clinical studies have associated short and long-termsolvent exposures with cognitive dysfunction including att...

DFT Studies of SN2 Dechlorination of Polychlorinated Biphenyls.

PubMed

Krzemińska, Agnieszka; Paneth, Piotr

2016-06-21

Nucleophilic dechlorination of all 209 PCBs congeners by ethylene glycol anion has been studied theoretically at the DFT level. The obtained Gibbs free energies of activation are in the range 7-22 kcal/mol. The reaction Gibbs free energies indicate that all reactions are virtually irreversible. Due to geometric constrains these reactions undergo rather untypical attack with attacking oxygen atom being nearly perpendicular to the attacked C-Cl bond. The most prone to substitution are chlorine atoms that occupy ortho- (2, 2', 6, 6') positions. These results provide extensive information on the PEG/KOH dependent PCBs degradation. They can also be used in further developments of reaction class transition state theory (RC-TST) for description of complex reactive systems encountered for example in combustion processes.

Assessment of chloroethene biodegradation in the subsurface by microbiological, molecular and isotopic tools

NASA Astrophysics Data System (ADS)

Schmidt, K. R.; Kranzioch, I.; Heidinger, M.; Ertl, S.; Tiehm, A.

2012-04-01

A multiple lines of evidence approach to assess the biodegradation potential of contaminated sites includes - site investigation analysing pollutant distribution (compounds, concentrations, isotopic composition) and hydrochemical conditions (redox conditions) - determination of the presence of pollutant degrading bacteria in the field by microbiological (most probable number, MPN) and molecular (polymerase chain reaction, PCR) methods - analysis of degradation processes in the laboratory by microcosms with determination of site specific isotopic enrichment factors enabling the quantification of biodegradation processes in the field. Results will be shown of the application of such a multiple lines of evidence approach at a chloroethene-contaminated site in Frankenthal, Germany. In anaerobic groundwater microcosms, reductive transformation of perchloroethene (PCE) and trichloroethene (TCE) was observed to mainly proceed to cis-1,2-dichloroethene (cDCE). 16S-PCR analysis showed a wide distribution of halorespiring bacteria capable of PCE degradation to cDCE, whereas Dehalococcoides - the only organisms described so far being able of complete reductive dechlorination down to ethene - was only found in one groundwater sample. Aerobic microcosms showed metabolic degradation of the lower chlorinated compounds cDCE and vinyl chloride (VC). Co-metabolic degradation of cDCE with VC as auxiliary substrate occurred, too. Significant stable carbon isotope fractionation was observed during anaerobic degradation of PCE and TCE as well as during aerobic degradation of cDCE and VC. Compiling the results of the different assessment methods, sequential dechlorination - PCE/TCE to cDCE anaerobically and cDCE to CO2 aerobically - was demonstrated to occur at the Frankenthal site. The extent of biodegradation in the field was calculated based on the enrichment factors determined in microcosms and the 13C-isotopic composition of the contaminants on site. The application of molecular

REMEDIATION OF TCE-CONTAMINATED GROUNDWATER BY A PERMEABLE REACTIVE BARRIER FILLED WITH PLANT MULCH (BIOWALL)

EPA Science Inventory

A pilot-scale permeable reactive barrier filled with plant mulch was installed at Altus Air Force Base (in Oklahoma, USA) to treat trichloroethylene (TCE) contamination in ground water emanating from a landfill. The barrier was constructed in June 2002. It was 139 meters long, 7 ...

EFFECTIVE REMOVAL OF TCE IN A LABORATORY MODEL OF A PRB CONSTRUCTED WITH PLANT MULCH

EPA Science Inventory

Ground water contaminated with TCE is commonly treated with a permeable reactive barrier (PRB) constructed with zero-valence iron. The cost of iron as the reactive matrix has driven a search for less costly alternatives, and composted plant mulch has been used as an alternative ...

Documents for SBAR Panel: Trichloroethylene (TCE); Regulation of Use in Vapor Degreasing under TSCA §6(a)

EPA Pesticide Factsheets

SBAR panel to to address risks resulting from the manufacture, import, processing, distribution in commerce, and use of chemicals, as well as any manner or method of disposal of chemicals: Trichloroethylene (TCE)

LONG-TERM RECOVERY OF PCB-CONTAMINATED SEDIMENTS AT THE LAKE HARTWELL SUPERFUND SITE: PCB DECHLORINATION. 1. END-MEMBER CHARACTERIZATION

EPA Science Inventory

Under anaerobic conditions, such as those typically found in buried sediments, the primary metabolic pathway for polychlorinated biphenyls (PCBs) is reductive dechlorination in which chlorine removal and substitution with hydrogen by bacteria result in a reduced organic compound ...

Microbial degradation of chloroethenes in groundwater systems

NASA Astrophysics Data System (ADS)

Bradley, Paul M.

The chloroethenes, tetrachloroethene (PCE) and trichloroethene (TCE) are among the most common contaminants detected in groundwater systems. As recently as 1980, the consensus was that chloroethene compounds were not significantly biodegradable in groundwater. Consequently, efforts to remediate chloroethene-contaminated groundwater were limited to largely unsuccessful pump-and-treat attempts. Subsequent investigation revealed that under reducing conditions, aquifer microorganisms can reductively dechlorinate PCE and TCE to the less chlorinated daughter products dichloroethene (DCE) and vinyl chloride (VC). Although recent laboratory studies conducted with halorespiring microorganisms suggest that complete reduction to ethene is possible, in the majority of groundwater systems reductive dechlorination apparently stops at DCE or VC. However, recent investigations conducted with aquifer and stream-bed sediments have demonstrated that microbial oxidation of these reduced daughter products can be significant under anaerobic redox conditions. The combination of reductive dechlorination of PCE and TCE under anaerobic conditions followed by anaerobic microbial oxidation of DCE and VC provides a possible microbial pathway for complete degradation of chloroethene contaminants in groundwater systems. Résumé Les chloroéthanes, tétrachloroéthane (PCE) et trichloroéthane (TCE) sont parmi les polluants les plus communs trouvés dans les aquifères. Depuis les années 1980, on considère que les chloroéthanes ne sont pas significativement biodégradables dans les aquifères. Par conséquent, les efforts pour dépolluer les nappes contaminées par des chloroéthanes se sont limités à des tentatives de pompage-traitement globalement sans succès. Des travaux ultérieurs ont montré que dans des conditions réductrices, des micro-organismes présents dans les aquifères peuvent, par réduction, dégrader les PCE et TCE en composés moins chlorés, comme le dichlor

ENVIROMETAL TECHNOLOGIES, INC. - METAL-ENHANCED DECHLORINATION OF VOLATILE ORGANIC COMPOUNDS USING AN ABOVE-GROUND REACTOR, INNOVATIVE TECHNOLOGY EVALUATION REPORT

EPA Science Inventory

EnviroMetal Technology's metal-enhanced dechlorination technology employs an electrochemical process that involves oxidation of iron and reductive dehalogenation of halogenated VOCs in aqueous media. The process can be operated as an above ground reactor or can alternatively perf...

Vacuum distillation of a mixture of LiCl-KCl eutectic salts and RE oxidative precipitates and a dechlorination and oxidation of RE oxychlorides.

PubMed

Eun, Hee Chul; Yang, Hee Chul; Cho, Yung Zun; Lee, Han Soo; Kim, In Tae

2008-12-30

In this study, a vacuum distillation of a mixture of LiCl-KCl eutectic salt and rare-earth oxidative precipitates was performed to separate a pure LiCl-KCl eutectic salt from the mixture. Also, a dechlorination and oxidation of the rare-earth oxychlorides was carried out to stabilize a final waste form. The mixture was distilled under a range of 710-759.5Torr of a reduced pressure at a fixed heating rate of 4 degrees C/min and the LiCl-KCl eutectic salt was completely separated from the mixture. The required time for the salt distillation and the starting temperature for the salt vaporization were lowered with a reduction in the pressure. Dechlorination and oxidation of the rare-earth oxychlorides was completed at a temperature below 1300 degrees C and this was dependent on the partial pressure of O2. The rare-earth oxychlorides (NdOCl/PrOCl) were transformed to oxides (Nd2O3/PrO2) during the dechlorination and oxidation process. These results will be utilized to design a concept for a process for recycling the waste salt from an electrorefining process.

Oxidative degradation and toxicity reduction of trichloroethylene (TCE) in water using TiO2/solar light: comparative study of TiO2 slurry and immobilized systems.

PubMed

Cho, Il-Hyoung; Park, Jae-Hong; Kim, Young-Gyu

2005-01-01

A solar-driven, photocatalyzed degradation system using TiO2 slurry and immobilized systems was constructed and applied to the degradation of trichloroethylene (TCE) contaminated water using TiO2 with solar light. The experiments were carried out under constant weather conditions on a sunny day. Solar photocatalytic treatment efficiency of the solar light/TiO2 slurry system was compared with that of the solar light/TiO2 immobilized system. The operation of the solar light/TiO2 slurry and immobilized systems showed 100% (TiO2 slurry system), 80% (TiO2 immobilized system) degradation of the TCE after 6 h, with a chloride production yield of approximately 89% (TiO2 slurry system), 72% (TiO2 immobilized system). The oxidants such as H2O2 and S2O8(2-) in the TiO2 slurry and immobilized systems increased TCE degradation rate by suppressing the electron/hole recombination process. The degradation rate and relative toxicity reduction of TCE followed the order of solar light/TiO2 slurry + S2O8(2-) > solar light/TiO2 slurry + H2O2 > solar light/TiO2 immobilized + S2O8(2-) > solar light/TiO2 slurry > solar light/TiO2 immobilized + H2O2 > solar light/TiO2 immobilized. Finally, following to the toxicity result, the acute toxicity was reduced by below toxicity endpoint (EC50 concentration) following the treatment. It means that many of the metabolites of TCE reduction are less toxic to Vibrio fischeri than the parent compound. Based on these results, TCE can be efficiently and safely treated in a solar-driven, photocatalyzed degradation system.

Sulfidation of Nano Zerovalent Iron (nZVI) for Improved Selectivity During In-Situ Chemical Reduction (ISCR).

PubMed

Fan, Dimin; O'Brien Johnson, Graham; Tratnyek, Paul G; Johnson, Richard L

2016-09-06

The high reactivity of nano zerovalent iron (nZVI) leads to inefficient treatment due to competition with various natural reductant demand (NRD) processes, especially the reduction of water to hydrogen. Here we show that this limitation can be alleviated by sulfidation (i.e., modification by reducing sulfur compounds). nZVI synthesized on carboxylmethylcelluose (CMC-nZVI) was sulfidated with either sulfide or dithionite. The reactivity of the resulting materials was examined with three complementary assays: (i) direct measurement of hydrogen production, (ii) reduction of a colorimetric redox probe (indigo disulfonate, I2S), and (iii) dechlorination of trichloroethylene (TCE). The results indicate that sulfidation at S/Fe molar ratios of ≥0.3, effectively eliminates reaction with water, but retains significant reactivity with TCE. However, sulfidation with sulfide leaves most of the nZVI as Fe(0), whereas dithionite converts a majority of the nZVI to FeS (thus consuming much of the reducing capacity originally provided by the Fe(0)). Simplified numerical models show that the reduction kinetics of I2S and TCE are mainly dependent on the initial reducing equivalents and that the TCE reduction rate is affected by the aging of FeS. Overall, the results suggest that pretreatment of nZVI with reducing sulfur compounds could result in substantial improvement in nZVI selectivity.

LONG-TERM RECOVERY OF PCB-CONTAMINATED SEDIMENTS AT THE LAKE HARTWELL SUPERFUND SITE: PCB DECHLORINATION. 2. RATES AND EXTENT

EPA Science Inventory

This paper reports on extensive polychlorinated biphenyl (PCB) dechlorination measured in Lake Hartwell (Pickens County, SC) sediments. Vertical sediment cores were collected from 18 locations in Lake Hartwell (Pickens County, SC) and analyzed in 5-cm increments for PCB congeners...

Abiotic Removal of TCE and cis-DCE by Magnetite under Aerobic Conditions in Ground Water (Maryland)

EPA Science Inventory

The former Twin Cities Army Ammunition Plant (TCAAP) is located just north of St. Paul, Minnesota. Disposal of chlorinated solvents at the Building102 site on the TCAAP contaminated groundwater in the shallow, unconsolidated sand aquifer with TCE and cis-DCE. Concentrations of ...

FIELD SCALE EVALUATION OF TREATMENT OF TCE IN A BIOWALL AT THE OU-1 SITE

EPA Science Inventory

A passive reactive barrier (Biowall) was installed at the OU-1 site at Altus Air Force Base, Oklahoma to treat TCE contamination in ground water from a landfill. Depth to ground water varies from 1.8 to 2.4 meters below land surface. To intercept and treat the plume of contamin...

ABIOTIC REACTIONS MAY BE THE MOST IMPORTANT MECHANISM IN NATURAL ATTENUATION OF CHLORINATED SOLVENTS

EPA Science Inventory

The EPA Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water was developed with the assumption that natural biological reductive dechlorination was the only important mechanism for destruction of chlorinated solvents and their reduction ...

Reinterpreting the importance of oxygen-based biodegradation in chloroethene-contaminated groundwater

USGS Publications Warehouse

Bradley, Paul M.

2011-01-01

Chlororespiration is common in shallow aquifer systems under conditions nominally identified as anoxic. Consequently, chlororespiration is a key component of remediation at many chloroethene-contaminated sites. In some instances, limited accumulation of reductive dechlorination daughter products is interpreted as evidence that natural attenuation is not adequate for site remediation. This conclusion is justified when evidence for parent compound (tetrachloroethene, PCE, or trichloroethene, TCE) degradation is lacking. For many chloroethene-contaminated shallow aquifer systems, however, nonconservative losses of the parent compounds are clear but the mass balance between parent compound attenuation and accumulation of reductive dechlorination daughter products is incomplete. Incomplete mass balance indicates a failure to account for important contaminant attenuation mechanisms and is consistent with contaminant degradation to nondiagnostic mineralization products like CO2. While anoxic mineralization of chloroethene compounds has been proposed previously, recent results suggest that oxygen-based mineralization of chloroethenes also can be significant at dissolved oxygen concentrations below the currently accepted field standard for nominally anoxic conditions. Thus, reassessment of the role and potential importance of low concentrations of oxygen in chloroethene biodegradation are needed, because mischaracterization of operant biodegradation processes can lead to expensive and ineffective remedial actions. A modified interpretive framework is provided for assessing the potential for chloroethene biodegradation under different redox conditions and the probable role of oxygen in chloroethene biodegradation.

Microbial mineralization of cis-dichloroethene and vinyl chloride as a component of natural attenuation of chloroethene contaminants under conditions identified in the field as anoxic

USGS Publications Warehouse

Bradley, Paul M.

2012-01-01

Chlororespiration is a key component of remediation at many chloroethene-contaminated sites. In some instances, limited accumulation of reductive dechlorination daughter products may suggest that natural attenuation is not adequate for site remediation. This conclusion is justified when evidence for parent compound (tetrachloroethene, PCE, or trichloroethene, TCE) degradation is lacking. For many chloroethene-contaminated shallow aquifer systems, however, non-conservative losses of the parent compounds are clear but the mass balance between parent compound attenuation and accumulation of reductive dechlorination daughter products is incomplete. Incomplete mass balance indicates a failure to account for important contaminant attenuation mechanisms, and is consistent with contaminant degradation to non-diagnostic mineralization products. An ongoing technical debate over the potential for mineralization of dichloroethene (DCE) and vinyl chloride (VC) to CO2 in the complete absence of diatomic oxygen has largely obscured the importance of microbial DCE/VC mineralization at dissolved oxygen (DO) concentrations below the current field standard (DO < 0.1-0.5 milligrams per liter) for nominally anoxic conditions. This study demonstrates that oxygen-based microbial mineralization of DCE and VC can be substantial under field conditions that are frequently characterized as "anoxic." Because mischaracterization of operant contaminant biodegradation processes can lead to expensive and ineffective remedial actions, a modified framework for assessing the potential importance of oxygen during chloroethene biodegradation was developed.

The effects of co-contaminants and native wetland sediments on the activity and dominant transformation mechanisms of a 1,1,2,2-tetrachloroethane (TeCA)-degrading enrichment culture

USGS Publications Warehouse

Lorah, Michelle M.; Schiffmacher, Emily N.; Becker, Jennifer G.; Voytek, Mary A.

2016-01-01

Bioremediation strategies, including bioaugmentation with chlorinated ethene-degrading enrichment cultures, have been successfully applied in the cleanup of subsurface environments contaminated with tetrachloroethene (PCE) and/or trichloroethene (TCE). However, these compounds are frequently found in the environment as components of mixtures that may also contain chlorinated ethanes and methanes. Under these conditions, the implementation of bioremediation may be complicated by inhibition effects, particularly when multiple dehalorespirers are present. We investigated the ability of the 1,1,2,2-tetrachloroethane (TeCA)-dechlorinating culture WBC-2 to biotransform TeCA alone, or a mixture of TeCA plus PCE and carbon tetrachloride (CT), in microcosms. The microcosms contained electron donors provided to biostimulate the added culture and sediment collected from a wetland where numerous “hotspots” of contamination with chlorinated solvent mixtures exist. The dominant TeCA biodegradation mechanism mediated by the WBC-2 culture in the microcosms was different in the presence of these wetland sediments than in the sediment-free enrichment culture or in previous WBC-2 bioaugmented microcosms and column tests conducted with wetland sediment collected at nearby sites. The co-contaminants and their daughter products also inhibited TeCA biodegradation by WBC-2. These results highlight the need to conduct biodegradability assays at new sites, particularly when multiple contaminants and dehalorespiring populations are present.

Degradation of trichloroethylene (TCE) by nanoscale zero-valent iron (nZVI) immobilized in alginate bead.

PubMed

Kim, Hojeong; Hong, Hye-Jin; Jung, Juri; Kim, Seong-Hye; Yang, Ji-Won

2010-04-15

Nowadays, many researchers have studied the environmental application of the nanoscale zero-valent iron (nZVI) and several field applications for the groundwater remediation have been reported. Still, there are many concerns on the fate and transport of the nZVI and the corresponding risks. To avoid such concerns, it was investigated to immobilize nZVI in a support and then it was applied to degrade trichloroethylene (TCE). The nZVI and palladium-doped nZVI (Fe(0)- and Fe/Pd-alginate) were immobilized in the alginate bead where ferric and barium ions are used as the cross-linking cations of the bead. According to TEM (transmission electron microscopy), the size of the immobilized ZVI was as small as a few nanometers. From the surface analysis of the Fe/Pd-alginate, it is found that the immobilized nZVI has the core-shell structure. The core is composed of single crystal Fe(0), while most of irons on the surface are oxidized to Fe(3+). When 50 g/L of Fe/Pd-alginate (3.7 g Fe/L) was introduced to the aqueous solution, >99.8% of TCE was removed and the release of metal from the support was <3% of the loaded iron. The removal of TCE by Fe/Pd-alginate followed pseudo-first-order kinetics. The observed pseudo-first-order reaction constant (k(obs)) of Fe/Pd-alginate was 6.11 h(-1) and the mass normalized rate constant (k(m)) was 1.6 L h(-1) g(-1). The k(m) is the same order of magnitude with that of iron nanoparticles. In conclusion, it is considered that Fe/Pd-alginate can be used efficiently in the treatment of chlorinated solvent. 2009 Elsevier B.V. All rights reserved.

Investigating the efficiency of microscale zero valent iron-based in situ reactive zone (mZVI-IRZ) for TCE removal in fresh and saline groundwater.

PubMed

Xin, Jia; Tang, Fenglin; Yan, Jing; La, Chenghong; Zheng, Xilai; Liu, Wei

2018-06-01

In this study, long-term column experiments were conducted in three media (Milli-Q water, fresh groundwater and saline groundwater) to evaluate the trichloroethylene (TCE) removal performance, electron efficiency (EE), and permeability loss of a microscale zero valent iron-based in situ reactive zone (mZVI-IRZ) under different field conditions. A potential scenario of in situ contamination plume remediation was simulated by adding a TCE-containing influent to columns filled with mixed mZVI particles and silica sand at a flow rate of 4 mL h -1 for 6 months. Results showed that, over the course of 100 pore volumes (PV) for 6 months, mZVI displayed the lowest TCE breakthrough rate (0.0026 PV -1 ) and highest TCE removal capacity (43.72 mg) but the poorest EE value (25-40%) in saline groundwater. Mineral characterization (SEM, XRD), ion concentration analysis, and geochemical modeling corroborated that different dominant solid precipitates (magnetite, siderite, dolomite/magnetite) were identified inside the three columns. The column containing saline groundwater experienced the greatest porosity loss, approximately 30.23 mL over the course of 100 PVs. This study illustrates that, to improve designs of mZVI-IRZs, EE as well as hydraulic conductivity should be taken into consideration for predictive evaluations. Copyright © 2018 Elsevier B.V. All rights reserved.

A three-electrode column for Pd-catalytic oxidation of TCE in groundwater with automatic pH-regulation and resistance to reduced sulfur compound foiling.

PubMed

Yuan, Songhu; Chen, Mingjie; Mao, Xuhui; Alshawabkeh, Akram N

2013-01-01

A hybrid electrolysis and Pd-catalytic oxidation process is evaluated for degradation of trichloroethylene (TCE) in groundwater. A three-electrode, one anode and two cathodes, column is employed to automatically develop a low pH condition in the Pd vicinity and a neutral effluent. Simulated groundwater containing up to 5 mM bicarbonate can be acidified to below pH 4 in the Pd vicinity using a total of 60 mA with 20 mA passing through the third electrode. By packing 2 g of Pd/Al(2)O(3) pellets in the developed acidic region, the column efficiency for TCE oxidation in simulated groundwater (5.3 mg/L TCE) increases from 44 to 59 and 68% with increasing Fe(II) concentration from 0 to 5 and 10 mg/L, respectively. Different from Pd-catalytic hydrodechlorination under reducing conditions, this hybrid electrolysis and Pd-catalytic oxidation process is advantageous in controlling the fouling caused by reduced sulfur compounds (RSCs) because the in situ generated reactive oxidizing species, i.e., O(2), H(2)O(2) and OH, can oxidize RSCs to some extent. In particular, sulfite at concentrations less than 1 mM even greatly increases TCE oxidation by the production of SO(4)(•-), a strong oxidizing radical, and more OH. Copyright © 2012 Elsevier Ltd. All rights reserved.

Abiotic and Biotic Transformation of TCE under Sulfate Reducing Conditions: the Role of Spatial Heterogeneity (Monterey, CA)

EPA Science Inventory

At a number of sites in the USA, passive reactive barriers built with shredded plant mulch have been constructed to treat ground water contaminated with TCE. These barriers are called biowalls because anaerobic biodegradation of the plant mulch is expected to provide substrates ...

Natural attenuation of trichloroethylene in fractured shale bedrock.

PubMed

Lenczewski, M; Jardine, P; McKay, L; Layton, A

2003-07-01

This paper describes one of the first well-documented field examples of natural attenuation of trichloroethylene (TCE) in groundwater in a fractured shale bedrock. The study was carried out adjacent to a former waste burial site in Waste Area Grouping 5 (WAG5) on the Oak Ridge Reservation, Oak Ridge, TN. A contaminant plume containing TCE and its daughter products were detected downgradient from the buried waste pits, with most of the contamination occurring in the upper 6 m of the bedrock. The monitoring well array consists of a 35-m-long transect of multilevel sampling wells, situated along a line between the waste pits and a seep which discharges into a small stream. Concentrations of volatile organic carbons (VOCs) were highest in the waste trenches and decreased with distance downgradient towards the seep. Sampling wells indicated the presence of overlapping plumes of TCE, cis-dichloroethylene (cDCE), vinyl chloride (VC), ethylene, ethane, and methane, with the daughter products extending further downgradient than the parent (TCE). This type of distribution suggests anaerobic biodegradation. Measurements of redox potential at the site indicated that iron-reduction, sulfate reduction, and potentially methanogensis were occurring and are conducive to dechlorination of TCE. Bacteria enrichment of groundwater samples revealed the presence of methanotrophs, methanogens, iron-reducing bacteria and sulfate-reducing bacteria, all of which have previously been implicated in anaerobic biodegradation of TCE. 16S rDNA sequence from DNA extracted from two wells were similar to sequences of organisms previously implicated in the anaerobic biodegradation of chlorinated solvents. The combined data strongly suggest that anaerobic biodegradation of the highly chlorinated compounds is occurring. Aerobic biodegradation may also be occurring in oxygenated zones, including near a seep where groundwater exits the site, or in the upper bedrock during seasonal fluctuations in water

CHANGES IN ENANTIOMERIC FRACTIONS DURING MICROBIAL REDUCTIVE DECHLORINATION OF PCB132, PCB149, AND AROCLOR 1254 IN LAKE HARTWELL SEDIMENT MICROCOSMS

EPA Science Inventory

Enantioselectivity of microbial reductive dechlorination of chiral PCBs in sediments from Lake Hartwell, SC, was determined by microcosm studies and enantiomer-specific GC analysis. Sediments from two locations in the vicinity of the highest levels of PCB contamination were used...

Degradation of soil-sorbed trichloroethylene by stabilized zero valent iron nanoparticles: Effects of sorption, surfactants, and natural organic matter

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

Zhang, Man; He, Feng; Zhao, Dongye

2011-01-01

Zero valent iron (ZVI) nanoparticles have been studied extensively for degradation of chlorinated solvents in the aqueous phase, and have been tested for in-situ remediation of contaminated soil and groundwater. However, little is known about its effectiveness for degrading soil-sorbed contaminants. This work studied reductive dechlorination of trichloroethylene (TCE) sorbed in two model soils (a potting soil and Smith Farm soil) using carboxymethyl cellulose (CMC) stabilized Fe-Pd bimetallic nanoparticles. Effects of sorption, surfactants and dissolved organic matter (DOC) were determined through batch kinetic experiments. While the nanoparticles can effectively degrade soil-sorbed TCE, the TCE degradation rate was strongly limited bymore » desorption kinetics, especially for the potting soil which has a higher organic matter content of 8.2%. Under otherwise identical conditions, {approx}44% of TCE sorbed in the potting soil was degraded in 30 h, compared to {approx}82% for Smith Farm soil (organic matter content = 0.7%). DOC from the potting soil was found to inhibit TCE degradation. The presence of the extracted SOM at 40 ppm and 350 ppm as TOC reduced the degradation rate by 34% and 67%, respectively. Four prototype surfactants were tested for their effects on TCE desorption and degradation rates, including two anionic surfactants known as SDS (sodium dodecyl sulfate) and SDBS (sodium dodecyl benzene sulfonate), a cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide, and a non-ionic surfactant Tween 80. All four surfactants were observed to enhance TCE desorption at concentrations below or above the critical micelle concentration (cmc), with the anionic surfactant SDS being most effective. Based on the pseudo-first-order reaction rate law, the presence of 1 x cmc SDS increased the reaction rate by a factor of 2.5 when the nanoparticles were used for degrading TCE in a water solution. SDS was effective for enhancing degradation of TCE sorbed in Smith

Reductive dechlorination of atrazine catalyzed by metalloporphyrins.

PubMed

Nelkenbaum, Elza; Dror, Ishai; Berkowitz, Brian

2009-03-01

Atrazine (2-chloro-4-(ethylamine)-6-(isopropylamine)-s-triazine) is a widely used herbicide which is considered a persistent groundwater contaminant. Its selective transformation mediated by cobalt or nickel porphyrins was studied in aqueous solutions at room temperature and ambient pressure. Several metalloporphyrins were examined as catalysts for the reaction and all yielded the same reaction, transforming atrazine solely to the seldomly reported form 2,4-bis(ethylamine)-6-methyl-s-triazine. The reaction involves dechlorination and migration of a methyl group to yield a symmetric product. Nickel 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP) was activated by nanosized zero-valent iron (nZVI) while cobalt porphyrins (TMPyP, 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphine-(TP(OH)P) and 4,4',4'',4'''-(porphine-5,10,15,20-tetrayl)tetrakis (benzenesulfonic acid)-(TBSP)) were activated by titanium(III) citrate as the electron donor. The effect of pH on atrazine transformation was demonstrated for the catalytic system of TP(OH)P-Co/Ti(III) citrate. Finally, a comparison of the reactivities of cobalt TMPyP and TP(OH)P was given and the differences discussed.

Electron efficiency of nZVI does not change with variation of environmental parameters.

PubMed

Schöftner, Philipp; Waldner, Georg; Lottermoser, Werner; Stöger-Pollach, Michael; Freitag, Peter; Reichenauer, Thomas G

2015-12-01

Nanoscale zero-valent iron particles (nZVI) are already applied for in-situ dechlorination of halogenated organic contaminants in the field. We performed batch experiments whereby trichloroethene (TCE) was dehalogenated by nZVI under different environmental conditions that are relevant in practice. The tested conditions include different ionic strengths, addition of polyelectrolytes (carboxymethylcellulose and ligninsulphonate), lowered temperature, dissolved oxygen and different particle contents. Particle properties were determined by Mössbauer spectroscopy, XRD, TEM, SEM, AAS and laser obscuration time measurements. TCE dehalogenation and H2 evolution were decelerated by reduced ionic strength, addition of polyelectrolytes, temperature reduction, the presence of dissolved oxygen and reduced particle content. The partitioning of released electrons between reactions with the contaminant vs. with water (selectivity) was low, independent of the tested conditions. Basically out of hundred electrons that were released via nZVI oxidation only 3.1±1.4 were used for TCE dehalogenation. Even lower selectivities were observed at TCE concentrations below 3.5 mg l(-1), hence particle modifications and/or combination of nZVI with other remediation technologies seem to be necessary to reach target concentrations for remediation. Our results suggest that selectivity is particle intrinsic and not as much condition dependent, hence particle synthesis and potential particle modifications of nZVI particles may be more important for optimization of the pollutant degradation rate, than tested environmental conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Chelate-Modified Fenton Reaction for the Degradation of Trichloroethylene in Aqueous and Two-Phase Systems

PubMed Central

Lewis, Scott; Lynch, Andrew; Bachas, Leonidas; Hampson, Steve; Ormsbee, Lindell; Bhattacharyya, Dibakar

2009-01-01

Abstract The primary objective of this research was to model and understand the chelate-modified Fenton reaction for the destruction of trichloroethylene (TCE) present in both the aqueous and organic (in the form of droplets) phases. The addition of a nontoxic chelate (L), such as citrate or gluconic acid, allows for operation at near-neutral pH and controlled release of Fe(II)/Fe(III). For the standard Fenton reaction at low pH in two-phase systems, an optimum H2O2:Fe(II) molar ratio was found to be between 1:1 and 2:1. Experimentation proved the chelate-modified Fenton reaction effectively dechlorinated TCE in both the aqueous and organic phases at pH 6–7 using low H2O2:Fe(II) molar ratios (4:1 to 8:1). Increasing the L:Fe ratio was found to decrease the rate of H2O2 degradation in both Fe(II) and Fe(III) systems at near-neutral pH. Generalized models were developed to predict the concentration of TCE in the aqueous phase and TCE droplet radius as a function of time using literature-reported hydroxyl radical reaction kinetics and mass transfer relationships. Additional aspects of this work include the reusability of the Fe–citrate complex under repeated H2O2 injections in real water systems as well as packed column studies for simulated groundwater injection. PMID:20418966

Simultaneous biodegradation of carbon tetrachloride and trichloroethylene in a coupled anaerobic/aerobic biobarrier.

PubMed

Kwon, Kiwook; Shim, Hojae; Bae, Wookeun; Oh, Juhyun; Bae, Jisu

2016-08-05

Simultaneous biodegradation of carbon tetrachloride (CT) and trichloroethylene (TCE) in a biobarrier with polyethylene glycol (PEG) carriers was studied. Toluene/methanol and hydrogen peroxide (H2O2) were used as electron donors and an electron acceptor source, respectively, in order to develop a biologically active zone. The average removal efficiencies for TCE and toluene were over 99.3%, leaving the respective residual concentrations of ∼12 and ∼57μg/L, which are below or close to the groundwater quality standards. The removal efficiency for CT was ∼98.1%, with its residual concentration (65.8μg/L) slightly over the standards. TCE was aerobically cometabolized with toluene as substrate while CT was anaerobically dechlorinated in the presence of electron donors, with the respective stoichiometric amount of chloride released. The oxygen supply at equivalent to 50% chemical oxygen demand of the injected electron donors supported successful toluene oxidation and also allowed local anaerobic environments for CT reduction. The originally augmented (immobilized in PEG carriers) aerobic microbes were gradually outcompeted in obtaining substrate and oxygen. Instead, newly developed biofilms originated from indigenous microbes in soil adapted to the coupled anaerobic/aerobic environment in the carrier for the simultaneous and almost complete removal of CT, TCE, and toluene. The declined removal rates when temperature fell from 28 to 18°C were recovered by doubling the retention time (7.2 days). Copyright © 2016 Elsevier B.V. All rights reserved.

Reductive dechlorination of trichloroethene DNAPL source zones: source zone architecture versus electron donor availability

NASA Astrophysics Data System (ADS)

Krol, M.; Kokkinaki, A.; Sleep, B.

2014-12-01

The persistence of dense-non-aqueous-phase liquids (DNAPLs) in the subsurface has led practitioners and regulatory agencies to turn towards low-maintenance, low-cost remediation methods. Biological degradation has been suggested as a possible solution, based on the well-proven ability of certain microbial species to break down dissolved chlorinated ethenes under favorable conditions. However, the biodegradation of pure phase chlorinated ethenes is subject to additional constraints: the continuous release of electron acceptor at a rate governed by mass transfer kinetics, and the temporal and spatial heterogeneity of DNAPL source zones which leads to spatially and temporally variable availability of the reactants for reductive dechlorination. In this work, we investigate the relationship between various DNAPL source zone characteristics and reaction kinetics using COMPSIM, a multiphase groundwater model that considers non-equilibrium mass transfer and Monod-type kinetics for reductive dechlorination. Numerical simulations are performed for simple, homogeneous trichloroethene DNAPL source zones to demonstrate the effect of single source zone characteristics, as well as for larger, more realistic heterogeneous source zones. It is shown that source zone size, and mass transfer kinetics may have a decisive effect on the predicted bio-enhancement. Finally, we evaluate the performance of DNAPL bioremediation for realistic, thermodynamically constrained, concentrations of electron donor. Our results indicate that the latter may be the most important limitation for the success of DNAPL bioremediation, leading to reduced bio-enhancement and, in many cases, comparable performance with water flooding.

Evaluating the potential for quantitative monitoring of in situ chemical oxidation of aqueous-phase TCE using in-phase and quadrature electrical conductivity

NASA Astrophysics Data System (ADS)

Hort, R. D.; Revil, A.; Munakata-Marr, J.; Mao, D.

2015-07-01

Electrical resistivity measurements can potentially be used to remotely monitor fate and transport of ionic oxidants such as permanganate (MnO4-) during in situ chemical oxidation (ISCO) of contaminants like trichloroethene (TCE). Time-lapse two-dimensional bulk conductivity and induced polarization surveys conducted during a sand tank ISCO simulation demonstrated that MnO4- plume movement could be monitored in a qualitative manner using bulk conductivity tomograms, although chargeability was below sensitivity limits. We also examined changes to in-phase and quadrature electrical conductivity resulting from ion injection, MnO2 and Cl- production, and pH change during TCE and humate oxidation by MnO4- in homogeneous aqueous solutions and saturated porous media samples. Data from the homogeneous samples demonstrated that inversion of the sand tank resistivity data using a common Tikhonov regularization approach was insufficient to recover an accurate conductivity distribution within the tank. While changes to in-phase conductivity could be successfully modeled, quadrature conductivity values could not be directly related to TCE oxidation product or MnO4- concentrations at frequencies consistent with field induced polarization surveys, limiting the utility of quadrature conductivity for monitoring ISCO.

INFLUENCE OF HYDRAULIC RETENTION TIME ON EXTENT OF PCE DECHLORINATION AND PRELIMINARY CHARACTERIZATION OF THE ENRICHMENT CULTURE. (R826694C703)

EPA Science Inventory

The extent of tetrachloroethene (PCE) dechlorination in two chemostats was evaluated as a function of hydraulic retention time (HRT). The inoculum of these chemostats was from an upflow anaerobic sludge blanket (UASB) reactor that rapidly converts PCE to vinyl chloride (VC) an...

Natural attenuation of chlorinated solvents at Area 6, Dover Air Force Base: Groundwater biogeochemistry

USGS Publications Warehouse

Witt, M.E.; Klecka, G.M.; Lutz, E.J.; Ei, T.A.; Grosso, N.R.; Chapelle, F.H.

2002-01-01

Monitored natural attenuation (MNA) has recently emerged as a viable groundwater remediation technology in the United States. Area 6 at Dover Air Force Base (Dover, DE) was chosen as a test site to examine the potential for MNA of tetrachloroethene (PCE) and trichloroethene (TCE) in groundwater and aquifer sediments. A "lines of evidence" approach was used to document the occurrence of natural attenuation. Chlorinated hydrocarbon and biogeochemical data were used to develop a site-specific conceptual model where both anaerobic and aerobic biological processes are responsible for the destruction of PCE, TCE, and daughter metabolites. An examination of groundwater biogeochemical data showed a region of depleted dissolved oxygen with elevated dissolved methane and hydrogen concentrations. Reductive dechlorination likely dominated in the anaerobic portion of the aquifer where PCE and TCE levels were observed to decrease with a simultaneous increase in cis-1,2-dichloroethene (cis-DCE), vinyl chloride (VC), ethene, and dissolved chloride. Near the anaerobic/aerobic interface, concentrations of cis-DCE and VC decreased to below detection limits, presumably due to aerobic biotransformation processes. Therefore, the contaminant and daughter product plumes present at the site appear to have been naturally attenuated by a combination of active anaerobic and aerobic biotransformation processes. ?? 2002 Elsevier Science B.V. All rights reserved.

Comparison of an Assay for Dehalococcoides DNA and a Microcosm Study in Predicting Reductive Dechlorination of Chlorinated Ethenes in the field

EPA Science Inventory

The study aims to compare the detection of 16S rRNA gene of Dehalococcoides species and the microcosm study for biotransformation in predicting reductive dechlorination of chlorinated ethylenes in ground water at hazardous waste sites. A total of 72 ground water samples were coll...

Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and 2HH2O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks

USGS Publications Warehouse

Révész, Kinga M.; Lollar, Barbara Sherwood; Kirshtein, Julie D.; Tiedeman, Claire; Imbrigiotta, Thomas E.; Goode, Daniel J.; Shapiro, Allen M.; Voytek, Mary A.; Lancombe, Pierre J.; Busenberg, Eurybiades

2014-01-01

An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in 2H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the δ13C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the δ2H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H2 gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE + VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average 13C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect of the

Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and ²HH₂O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks.

PubMed

Révész, Kinga M; Lollar, Barbara Sherwood; Kirshtein, Julie D; Tiedeman, Claire R; Imbrigiotta, Thomas E; Goode, Daniel J; Shapiro, Allen M; Voytek, Mary A; Lacombe, Pierre J; Busenberg, Eurybiades

2014-01-01

An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in ²H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the δ¹³C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the δ²H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H₂ gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE+VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average ¹³C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect

VISUALIZATION-BASED ANALYSIS FOR A MIXED-INHIBITION BINARY PBPK MODEL: DETERMINATION OF INHIBITION MECHANISM