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 The Reductive Dechlorination of Tetrachloroethylene Trichloroethylene and Carbon Tetrachloride Mixtures by Anaerobic Bacteria written by Rebecca Davis and published by . This book was released on 1999 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Exploring Anaerobic Reductive Dechlorination at Low PH Environments written by Yi Yang and published by . This book was released on 2012 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chlorinated aliphatic hydrocarbons (CAHs), such as tetrachloroethene (PCE) and trichloroethene (TCE), are ubiquitously pollutants in aquifer sediments and groundwater due to their heavy usage in industry and inappropriate disposal in the last century. Among about 1300 NPL (National Priorities List) sites, PCE and TCE are the two most frequently detected hazardous contaminants. Engineered bioremediation, including biostimulation and bioaugmentation, is a promising technology to clean those PCE and/or TCE contaminated sites. However, in many contaminated groundwater systems and hazardous waste sites, pH can be lower than 5 to 6. And release of HCl (strong acid) from anaerobic reductive dechlorination may lower the pH of groundwater. Besides, another main source of acidity comes from the fermentation of additive electron donors such as alcohols, organic acids and etc. Decreasing pH has been proved to be detrimental to the microbes that dechlorinated PCE or TCE. We intended to enrich and isolate microorganisms, which can perform anaerobic reductive dechlorination at low pH environments, by establishing microcosms, which will be beneficial to in situ bioremediation. We also screened some existing cultures for dechlorinating activity at low pH and determined the pH tolerance of consortium BDI, which had been successfully, applied for in situ bioremediation. Besides, this study investigated and explored the effects of solids on BDI consortium under low pH conditions. Generally, various dechlorinating pure cultures and consortium BDI show highest dechlorination rates and extent at circumneutral pH. Only Sulfurospirillum multivorans among tested cultures dechlorinated PCE to cDCE at pH 5.5. The screening efforts suggest that microbes capable of dechlorination below pH 5.5 are not common. It was observed that solids play an important role for enhancing microbial activities under low pH conditions. And BDI consortium can recover from up to 8 weeks exposure to low pH conditions, although the VC-to-ethene dechlorination step was affected.
Download or read book Reductive Dechlorination of High Concenrations of Tetrachloroethylene by Anaerobic Enrichment Culture written by Tao Wang and published by . This book was released on 1997 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dechlorination of Tetrachloroethene in Sulfate reducing Environments written by David Michael Bagley and published by . This book was released on 1989 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reductive Dechlorination of Tetrachloroethene in Polluted Aquifer Microcosms and Isolation of Anaerobic Bacteria from a Tetrachloroethene dechlorinating Enrichment written by Christopher D. Carlson and published by . This book was released on 1997 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Kinetic and Modeling Investigations of the Anaerobic Reductive Dechlorination of Chlorinated Ethylenes Using Single and Binary Mixed Cultures and Silicon based Organic Compounds as Slow release Substrates written by Seungho Yu and published by . This book was released on 2003 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Kinetics of Reductive Dechlorination of Trichloroethane TCA by Anaerobic Biofilms written by Rittmann Bruce E. and published by . This book was released on 1995 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Anaerobic Reductive Dechlorination of TCE and TCFE in TCE Contaminated Sediments written by Jae-Hyuk Lee and published by . This book was released on 2006 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research focused on the enhanced reductive dechlorination of trichloroethene (TCE) and its surrogate, trichlorofluoroethene (TCFE), using two bioremediation methods in anaerobic conditions. Two anaerobic bioremediation studies were conducted to investigate the effects of microbial communities in the presence of different electron acceptors and donors during anaerobic reductive dechlorination of TCE and TCFE. The first study was conducted in the groundwater microcosm bottles, filled with groundwater and sediments collected from Richmond site, CA. Parallel reductive dechlorination of TCE and TCFE was evaluated in the presence of fumarate and its product, succinate, while active reduction of high background concentrations of sulfate (2.5 mM) occurred. Because sulfate was assumed as a favorable electron acceptor during reductive dechlorination of chlorinated aliphatic hydrocarbons (CAHs), all microcosms receiving TCE and TCFE with substrates showed enhanced reductive dechlorination activity and even no substrate addition microcosms generated biotransformation products. From the electron mass balance calculations, more than 87.5% of electrons went to sulfate reduction and less than 10% of available electrons involved in dechlorination after sulfate reductions. After amending varying concentrations of sulfate (0 2.5 mM), no inhibition was found between reductive dechlorination of TCE and sulfate reduction. The result indicated that reductive dechlorination could be directly competed with sulfate reduction for available electrons. The second study investigated the effectiveness of in situ push-pull tests to evaluate bioaugmentation in physical aquifer models (PAMs) using dehalogenating strains to reductively dechlorinate TCE to ethene and TCFE to FE in the TCE contaminated sediments. Complete reduction of TCE to ethene occurred in less than 14 days with repeated additions of TCE (13.0 to 46.0 mg/L) and TCFE (15.0 mg/L) was completely transformed to FE in under 24 days. Increased rate and extent of dechlorination in the bioaugmented PAM compared to the nonaugmented control PAM indicated successful transport of the bioaugmented culture through the PAM. Similar transformation rates and time course of TCE and TCFE also indicated that TCFE was a bioprobe for reductive dechlorination of TCE. TCE and TCFE were transformed to cisdichloroethene (c-DCE) and cis-dichlorofluoroethene (c-DCFE) respectively at two of the three sampling ports after 50 days of incubation in the nonaugmented PAM indicating reductive dechlorination activity of indigenous microorganisms. The results showed that it is possible to increase the rate and extent of reductive dechlorination of TCE and TCFE by bioaugmentation and that push-pull tests are effective tools for detecting and quantifying these processes in situ. The third study focused on numerical modeling of the second study. The objectives of this study were (1) to evaluate a simplified method for estimating retardation factors for injected solutes and bioaugmented microorganisms using "pushpull" test injection phase breakthrough curves, (2) to identify whether bioaugmented microorganisms have kept the same transformation capacity of Evanite culture using Michaelis-Menten kinetics by the values provided by Yu et al. (2005) and to verify in situ rates of TCFE reductive dechlorination rates of push-pull tests by numerical modeling, and (3) to investigate a reasonable answer for the nonuniform recovery of ethene and FE during the activity test and the push-pull test. The bioaugmented microorganisms were effectively transported through Hanford sediment. The estimated retardation factor was 1.33. A numerical simulation predicted cell transport in the PAM as far as port 5. This was qualitatively confirmed by cell counts obtained during bioaugmentation but, cells were distributed nonuniformly. The transport test indicated that TCE and TCFE transport was relatively retarded compared to coinjected bromide tracer (retardation factors ranged from 1.33-1.62 for TCE and from 1.44-1.70 for TCFE). The modeling simulation of Michaelis-Menten kinetics for the activity test was well matched for reductive dechlorination rates for TCE and less dechlorinated ethenes using the previous published values of kmax and Ks of chlorinated ethenes by Yu et al. (2005); the model match indicated that the bioaugmented microorganisms kept the same transformation capacity as the original source, Evanite culture (Yu et al., 2005) over 4 months in the PAM. A numerical simulation resulted in the simple first order FE production rate of 1 day' using STOMP code (2002) and the value of FE production rate was in the range of the transformation rates of TCFE during the activity test. The bioaugmented PAM has caused slow loss of injected CAHs during the activity test and the push-pull test.
Download or read book Handbook of Property Estimation Methods for Chemicals written by Donald Mackay and published by CRC Press. This book was released on 2000-03-29 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: A complete restructuring and updating of the classic 1982 Handbook of Chemical Property Estimation Methods (commonly known as "Lyman's Handbook"), the Handbook of Property Estimation Methods for Chemicals: Environmental and Health Sciences reviews and recommends practical methods for estimating environmentally important properties of organic chemic
Download or read book Comparison of Alternative Hydrogen Donors for Anaerobic Reductive Dechlorination of Tetrachloroethene written by Donna Elaine Fennell and published by . This book was released on 1998 with total page 802 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Electron Donors on the Reductive Dechlorination of Trichlorofluoroethylene in Anaerobic Microcosms and in Situ Push pull Tests written by Erika N. Louie and published by . This book was released on 1999 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research focuses on the anaerobic transformation of trichloroethylene (TCE) that is occurring in the subsurface of the Evanite site in Corvallis, OR. Two anaerobic studies were conducted to investigate the effects of microbial communities in the presence of different electron donors during the anaerobic degradation of trichlorofluoroethylene (TCFE), and TCE. The first study was conducted in the groundwater microcosm bottles, filled with groundwater collected from the monitoring well 15 at the site. Because TCE was present in low concentrations in this well, TCFE was added to the microcosms as a surrogate compound that might be dehalogenated like TCE. Lactate, formate and hydrogen were evaluated as substrates for driving the anaerobic transformations. These substrates and products are potential electron donors to enhance the dechlorination of TCE and possibly TCFE. When injecting TCFE with one of the substrates in the microcosm bottles, a quick reduction of TCFE was observed to cis-dichlorofluoroethylene (cis-DCFE), and the transformation of the substrates to acetate. When TCFE and TCE were present as mixtures, a faster reduction of TCE to cis-DCE was observed compared to TCFE to cis-DCFE. The second study was an in-situ push-pull test at well15. Formate and TCFE were added to groundwater extracted from well 15. The amended groundwater was injected and extracted after a reaction time ranging from 3 to 5 hours. This study was conducted to determine the in-situ response to the addition of an electron donor to enhance the biotransformation of TCFE and TCE. During the push-pull test no transformation of formate to acetate was observed. Some TCFE was transformed to cis-DCFE. It is possible that another electron donor was present in the aquifer that lead TCE to transform to cis-DCE and furthermore to VC, and TCFE to cis-DCFE under reductive dechlorination conditions. These anaerobic systems involve the interaction of several reactions within the microbial population. Different transformations throughout the experimentation were an indication that the microbial population was active during the different stages of the study.
Download or read book Chemical Isotope and Molecular Analysis of Microbial Reductive Dechlorination of Tetrachloroethylene and Trichloroethylene written by Yiran Dong and published by . This book was released on 2009 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reductive Dechlorination of Chlorinated Ethenes by Mixed Anaerobic Consortia written by Bhaskar Ballapragada and published by . This book was released on 1996 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Anaerobic Dechlorination of TCE by Microorganisms Enriched from a Contaminated Groundwater Site written by Robert Brent Nielsen and published by . This book was released on 1999 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
