Download or read book Aerobic and Anaerobic Transformation of Cis Dichloroethene cis DCE and Vinyl Chloride VC Steps for Reliable Remediation written by and published by . This book was released on 2003 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: Considerable research has focused on the anaerobic transformation of PCE and TCE, two of the most common chlorinated solvents found in groundwater. However, relatively little is known about the types of microorganisms and specific environmental conditions associated with the dechlorination of dichloroethenes (DCEs) and vinyl chloride (VC). For the successful remediation of a contaminated site, the complete reduction to the environmentally benign products (e.g., ethene and inorganic chloride), or complete mineralization must be achieved. Recent research identified four different microbial processes that determine the fate of these compounds in groundwater. These processes include: * Anaerobic energy-yielding reductive dechlorination (chlororespiration) (Process 2) * Anaerobic energy-yielding oxidation (Process 3) * Aerobic cooxidation (Process 4) * Aerobic energy-yielding oxidation (Process 5).

Download or read book Characterization of the Aerobic Oxidation of Cis Dichloroethene and Vinyl Chloride in Support of Bioremediation of Chloroethene Contaminated Sites written by and published by . This book was released on 2004 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: The lesser chlorinated ethenes, cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC), are produced by anaerobic reductive dechlorination at subsurface sites contaminated by tetrachloroethene (PCE) and trichloroethene (TCE). Accumulation of VC and cDCE under anaerobic conditions limits the application of natural attenuation and enhanced reductive anaerobic biological in-situ treatment technologies (RABITT). Aerobic degradation of lesser chlorinated ethenes has been demonstrated, suggesting that sequential anaerobic/aerobic conditions may result in complete mineralization of PCE/TCE. However, our present understanding of the aerobic transformation potentials of cDCE and VC is limited, thus limiting the reliability of and confidence in natural and enhanced biological alternatives for site remediation. The objective of our project was to determine the prevalence and metabolic capabilities of microorganisms able to derive energy from aerobic oxidation of cDCE and/or VC in subsurface environments. The results help delineate the role of growth-coupled (vs. cometabolic) aerobic oxidation in the natural attenuation of lesser-chlorinated ethenes. Results provide the basis for improved site assessment, improved remedial-action decision-making, and more reliable bioremediation technologies. Our findings indicate that aerobic bacteria (Mycobacterium and Nocardioides strains) capable of growth-linked VC oxidation are widespread in the environment, and commonly found at chlorinated-ethene-contaminated sites. Aerobic assimilation of VC as a carbon source is therefore an ecologically significant phenomenon of equal or greater importance than cometabolic VC degradation. Based on their distribution, growth rates and kinetic parameters, we believe that Mycobacterium strains are most likely to be responsible for the aerobic natural attenuation of VC that has been observed at many sites.

Download or read book Exploring the Limits of Aerobic Vinyl Chloride and Cis dichloroethene Biodegradation Under Suboxic Conditions written by Patrick M. Richards and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An improved understanding of VC and cis-DCE biodegradation under low oxygen conditions could increase the efficiency and sustainability of CE remediation and to expand the use of Monitored Natural Attenuation as a remedial alternative. The overall objective of the studies presented here is to better define the role of aerobic VC and cis-DCE degrading bacteria under suboxic conditions, and to provide practical guidance for expanding the role of aerobic CE biodegradation as a site remediation strategy.

Download or read book Mechanisms Chemistry and Kinetics of the Anaerobic Biodegradation of Cis dichloroethylene and Vinyl Chloride First Annual Progress Report September 15 1996 September 14 1997 written by and published by . This book was released on 1997 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This three-year project is to study the anaerobic biological conversion of cis-1,2- dichloroethene (cDCE) and vinyl Chloride (VC) to ethene. The study is being conducted in three separate phases, the first to better understand the mechanisms involved in cDCE and VC biodegradation, the second to evaluate the chemistry of the processes involved, and the third, to study factors affecting reaction kinetics. Major funding is being provided by the US Department of Energy, but the DuPont Chemical Company has also agreed to directly cost-share on the project at a rate of $75,000 per year for the three year period. Tetrachloroethylene (PCE) and trichloroethylene (TCE) are solvents that are among the most widely occurring organic groundwater contaminants. The biological anaerobic reduction-of chlorinated aliphatic hydrocarbons (CAHs) such as PCE and TCE to cDCE and VC in groundwater was reported in the early 1980s. Further reduction of PCE and its intermediates to ethene was reported in 1989. Several pure cultures of anaerobic bacteria have been found to reductively dehalogenate PCE to cDCE Rates of reduction of PCE and TCE to cDCE are high and the need for electron donor addition for the reactions is small. However, the subsequent reduction of cDCE to VC, and then of VC to the harmless end product, ethene, is much slower and only recently has a pure culture been reported that is capable of reducing cDCE to VC or VC to ethene. There are numerous. reports of such conversions in mixed cultures. The reduction of cDCE and VC to ethene is where basic research is most needed and is the subject of this study.

Download or read book Mechanisms Chemistry and Kinetics of Anaerobic Biodegradation of Cis dichloroethylene and Vinyl Chloride 1998 Annual Progress Report written by and published by . This book was released on 1998 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of this study are to: (1) determine the biochemical pathways for reductive dehalogenation of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC), including identification of the enzymes involved, (2) determine the chemical requirements, especially the type and quantity of electron donors needed by the microorganisms for reductive dehalogenation, and (3) evaluate the kinetics of the process with respect to the concentration of both the electron donors and the electron acceptors (cDCE and VC). Progress has been made under each of the three primary objectives. One manuscript related to the first objective has been published. Manuscripts related to the other two objectives have been submitted for publication. Findings related to the three objectives are summarized.

Download or read book Synergistic Reductive Dechlorination of 1 1 1 trichloroethane and Trichloroethene and Aerobic Degradation of 1 4 dioxane written by Yihao Luo and published by . This book was released on 2018 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Widespread use of chlorinated solvents for commercial and industrial purposes makes co-occurring contamination by 1,1,1-trichloroethane (TCA), trichloroethene (TCE), and 1,4-dioxane (1,4-D) a serious problem for groundwater. TCE and TCA often are treated by reductive dechlorination, while 1,4-D resists reductive treatment. Aerobic bacteria are able to oxidize 1,4-D, but the biological oxidation of 1,4-D could be inhibited by TCA, TCE, and their reductive transformation products. To overcome the challenges from co-occurring contamination, I propose a two-stage synergistic system. First, anaerobic reduction of the chlorinated hydrocarbons takes place in a H2-based hollow-fiber "X-film" (biofilm or catalyst-coated film) reactor (MXfR), where "X-film" can be a "bio-film0" (MBfR) or an abiotic "palladium-film" (MPfR). Then, aerobic removal of 1,4-D and other organic compounds takes place in an O2-based MBfR. For the reductive part, I tested reductive bio-dechlorination of TCA and TCE simultaneously in an MBfR. I found that the community of anaerobic bacteria can rapidly reduce TCE to cis-dichloroethene (cis-DCE), but further reductions of cis-DCE to vinyl chloride (VC) and VC to ethene were inhibited by TCA. Also, it took months to grow a strong biofilm that could reduce TCA and TCE. Another problem with reductive dechlorination in the MBfR is that mono-chloroethane (MCA) was not reduced to ethane. In contrast, a film of palladium nano-particles (PdNPs), i.e., an MPfR, could the simultaneous reductions of TCA and TCE to mainly ethane, with only small amounts of intermediates: 1,1-dichloroethane (DCA) (~3% of total influent TCA and TCE) and MCA (~1%) in continuous operation. For aerobic oxidation, I enriched an ethanotrophic culture that could oxidize 1,4-D with ethane as the primary electron donor. An O2-based MBfR, inoculated with the enriched ethanotrophic culture, achieved over 99% 1,4-D removal with ethane as the primary electron donor in continuous operation. Finally, I evaluated two-stage treatment with a H2-based MPfR followed by an O2-MBfR. The two-stage system gave complete removal of TCA, TCE, and 1,4-D in continuous operation.

Download or read book Mechanisms Chemistry and Kinetics of Anaerobic Biodegradation of Cis Dichloroethene and Vinyl Chloride written by and published by . This book was released on 2000 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anaerobic biological processes can result in PCE and TCE destruction through conversion to cis-dichloroethene (cDCE) then to vinyl chloride (VC), and finally to ethene. Here, the chlorinated aliphatic hydrocarbons (CAHs) serve as electron acceptors in energy metabolism, requiring electron donors such as hydrogen from an external source. The purpose of this study was to learn more about the biochemistry of cDCE and VC conversion to ethene, to better understand the requirements for electron donors, and to determine factors affecting the rates of CAH degradation and organism growth. The biochemistry of reductive dehalogenation of VC was studied with an anaerobic mixed culture enriched on VC. In other studies on electron donor needs for dehalogenation of cDCE and VC, competition for hydrogen was found to occur between the dehalogenators and other microorganisms such as methanogens and homoacetogens in a benzoate-acclimated dehalogenating methanogenic mixed culture. Factors affecting the relative rates of destruction of the solvents and their intermediate products were evaluated. Studies using a mixed PCE-dehalogenating culture as well as the VC enrichment for biochemical studies suggested that the same species was involved in both cDCE and VC dechlorination, and that cDCE and VC competitively inhibited each other's dechlorination rate.

Download or read book The Contribution of Anaerobic Oxidation to Natural Attenuation of Cis 1 2 dichloroethene and Vinyl Chloride in Groundwater at an Industrial Site in Southern California written by Elizabeth P. Pickens and published by . This book was released on 2004 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Abiotic Reductive Dechlorination of Tetrachloroethylene and Trichloroethylene in Anaerobic Environments written by and published by . This book was released on 2009 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tetrachloroethylene (PCE) and trichloroethylene (TCE) are among the most frequently detected ground water contaminants at industrial sites, including many DoD facilities. Due to the high cost and uneven performance of traditional remediation technologies, monitored natural attenuation is emerging as a new technology for ground water remediation of pollutants such as these. In addition, there is growing interest in active remediation technologies that employ abiotic minerals. PCE and TCE are susceptible to reductive dechlorination by microorganisms as well as reduced minerals such as iron sulfide (FeS). Unlike biological reductive dechlorination, which often results in accumulation of harmful intermediates such as cis 1,2-dichloroethylene (cis-DCE) and vinyl chloride (VC), abiotic mineral-mediated dechlorination of PCE and TCE tends to result in complete transformation to non-toxic products such as acetylene. To more accurately apply natural attenuation and other remediation technologies, a greater understanding of the geochemical factors affecting the rates of purely abiotic reductive dechlorination of PCE and TCE is needed. Additional tools are also needed to determine whether or not abiotic reductive dechlorination is occurring at a particular site, and its relative importance compared to microbial dechlorination under a variety of geochemical conditions.

Download or read book Removal of Cis 1 2 dichloroethylene from Groundwater Using a Restored Wetland written by Todd Douglas DeJournett and published by . This book was released on 2006 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanisms Chemistry and Kinetics of Anaerobic Biodegradation of CDCE and VC written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Biological reductive dehalogenation of the chlorinated ethenes, tetrachloroethene (PCE) and trichloroethene (TCE) to cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and then ethene is of great interest both for natural attenuation and engineered remediation of these hazardous 2 contaminants in groundwater. This study was directed towards a better understanding of the factors affecting the rate and extent of conversions of cDCE and VC to ethene, which are generally considered the rate limiting steps in the overall process. The objectives of this study are to (1) determine the biochemical pathways for reductive dehalogenation of cDCE and VC, including identification of the enzymes involved, (2) determine the chemical requirements, especially the type and quantity of electron donors needed by the microorganisms for reductive dehalogenation, and (3) evaluate the kinetics of the process with respect to the concentration of both the electron donors and the electron acceptors (c DCE and VC).

Download or read book Laboratory Evaluation of Natural Attenuation and Enhanced Biodegradation of Trichloroethene Cis dichloroethene and Vinyl Chloride Under Anaerobic Conditions written by William B. Bratt and published by . This book was released on 2004 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 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 written by Paul M. Bradley and published by . This book was released on 2012 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Natural Attenuation for Groundwater Remediation written by Commission on Geosciences, Environment, and Resources and published by National Academies Press. This book was released on 2000-08-31 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past decade, officials responsible for clean-up of contaminated groundwater have increasingly turned to natural attenuation-essentially allowing naturally occurring processes to reduce the toxic potential of contaminants-versus engineered solutions. This saves both money and headaches. To the people in surrounding communities, though, it can appear that clean-up officials are simply walking away from contaminated sites. When is natural attenuation the appropriate approach to a clean-up? This book presents the consensus of a diverse committee, informed by the views of researchers, regulators, and community activists. The committee reviews the likely effectiveness of natural attenuation with different classes of contaminants-and describes how to evaluate the "footprints" of natural attenuation at a site to determine whether natural processes will provide adequate clean-up. Included are recommendations for regulatory change. The committee emphasizes the importance of the public's belief and attitudes toward remediation and provides guidance on involving community stakeholders throughout the clean-up process. The book explores how contamination occurs, explaining concepts and terms, and includes case studies from the Hanford nuclear site, military bases, as well as other sites. It provides historical background and important data on clean-up processes and goes on to offer critical reviews of 14 published protocols for evaluating natural attenuation.

Download or read book Bioaugmentation for Groundwater Remediation written by Hans F. Stroo and published by Springer Science & Business Media. This book was released on 2012-10-02 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: ​This volume provides a review of the past 10 to 15 years of intensive research, development and demonstrations that have been on the forefront of developing bioaugmentation into a viable remedial technology. This volume provides both a primer on the basic microbial processes involved in bioaugmentation, as well as a thorough summary of the methodology for implementing the technology. This reference volume will serve as a valuable resource for environmental remediation professionals who seek to understand, evaluate, and implement bioaugmentation.

Download or read book Transformation of Carbon Tetrachloride and Chloroform by Trichloroethene Respiring Anaerobic Mixed Cultures and Supernatant written by Kyle E. Vickstrom and published by . This book was released on 2016 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon tetrachloride (CT) and chloroform (CF) were transformed in batch reactor experiments conducted with anaerobic dechlorinating cultures and supernatant (ADC+S) harvested from continuous flow reactors. The Evanite (EV-5L) and Victoria/Stanford (VS-5L) cultures capable of respiring trichloroethene (TCE), 1,2-cis-dichloroethene (cDCE), and vinyl chloride (VC) to ethene (ETH) were grown in continuous flow reactors receiving an influent feed of saturated TCE (10 mM; 60 mEq) and formate (45 mM; 90 mEq) but no CT or CF. In all experiments, cells and supernatant were harvested from the chemostats and inoculated into batch reactors. Transformation of various concentrations of CT (0.86, 2.6, or 8.6 [micro]M), CF (2.1 or 21.1 [micro]M), dichloromethane (DCM; 23.1 [micro]M), and TCE (50 [micro]M) was examined. CT transformation was complete and exhibited pseudo-first order kinetics with CF as the primary measured transformation product in all treatments. Lesser amounts of DCM and carbon disulfide (CS2) were measured leading to an overall mass balance of 20-40% of the original mass as CT accounted for. An analytical first order solution was developed to model CT degradation and product formation under multiple conditions. Cells poisoned with 50 mM sodium azide (NaN3) catalyzed rapid and complete CT transformation suggesting a greater importance of redox active cofactors than live cells in the abiotic and cometabolic transformation. DCM and CS2 however were not produced in the poisoned treatments. TCE and CT simultaneous transformation occurred with an approximately two-fold increase in the CT degradation rate while maintaining complete TCE respiration to ETH. During the initial round of TCE respiration, the rate limiting step was VC to ETH, which was impacted by the presence of CT and CF. A subsequent addition of 50 [micro]M TCE showed a substantial decline in the rates of reductive dechlorination owing to the inhibitory effects of long term exposure to CF. The results clearly demonstrate that transformation can be promoted by anaerobic dechlorinating cultures and supernatant not previously acclimated to CT and CF. However, abiotic reactions account for much of the observed transformation. The role of CF inhibition on H2 utilization by the culture was also explored. Sodium formate was provided as a rapid release substrate, providing H2 as an electron donor. H2 partial pressures were tracked throughout the course of the kinetic experiments. The rapid transformation of CT to CF made it not possible to determine if CT inhibited H2 use by the anaerobic dechlorinating cultures. However, the rapid buildup and subsequent slow transformation of CF was found to reversibly inhibit H2 consumption for homoacetogenesis. It was found that an aqueous CF concentration above 0.4 [micro]M or 0.6 [micro]M inhibited H2 consumption by the EV-5L and VS-5L cultures, respectively. This result differed for the VS-5L culture when metabolizing TCE in the presence of CT and CF. The VS-5L culture consumed H2 at CF concentrations as high as 1.3 [micro]M. The culture may have been partially inhibited at CF concentrations greater than 0.6 [micro]M, which is shown by slower consumption of H2 than controls that did not contain CF. The results demonstrate that CF reversibly inhibits the consumption of H2 by the anaerobic dechlorinating cultures, and that more research is required to determine if it is through a chemical inhibition or toxicity.

Download or read book Enhanced Anaerobic Dechlorination of Chlorinated Solvents in the Capillary Fringe written by Sebastien Roupen Kaskassian and published by . This book was released on 2002 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bioventing under anaerobic reductive conditions has been presented as a potential bioremediation technology for dealing with highly chlorinated compounds present in the capillary fringe of a contaminated soil. Anaerobic reductive bioventing is similar to aerobic bioventing, providing the gas injected is free of oxygen and contains an electron donor, here hydrogen. The concept of bioventing is reported to be cost effective because of the in-situ solution it provides. Tetrachloroethylene (PCE) typically degrades under anaerobic, reductive conditions to Vinyl Chloride (VC), which can then be readily oxidized to environmentally benign products. In this study, enhanced anaerobic degradation of PCE in the unsaturated zone of the soil was simulated in soil microcosms. Four 15 cm high and 8 cm in diameter reactors were filled with a contaminated soil sampled at an Air Force base site. Each reactor allowed for a different set of conditions in components concentration in the gas feed. The work focused on optimizing the injection gas composition, monitoring electron donor delivery and utilization, and evaluating the treatment performance of PCE. Only one microcosm, fed with 0.5 % of hydrogen and 0.5 % of carbon dioxide, showed dechlorination of PCE into Trichloroethylene (TCE) and Cis-Dichloroethylene (Cis-DCE). This microcosm completely consumed hydrogen and produced little methane, thus proving that the feeding conditions favored dechlorinators over methanogenes. PCE sequential dehalogenation did not proceed further than Cis-DCE but the total quantity of intermediates produced accounted for more than 40 % of the PCE removed in that dechlorinating microcosm. In the other microcosms, PCE removal was mainly due to adsorption of PCE onto the soil organic matter. Adding biomass to the microcosm or increasing the gas retention time did not result in significant improvements of the microcosm dechlorinating activity. Pre-existing soil contaminants, mainly hydrocarbons, were not responsible for the lack of dechlorination. Gas feeding concentrations were the only parameters proved to trigger PCE sequential dechlorination since they helped maintaining reducing conditions. This study was useful to assess the potential for dechlorination of highly chlorinated compounds in a specific soil sample and to optimize the feed conditions to be applied when testing anaerobic bioventing in-situ.