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S.y. Yuan - One of the best experts on this subject based on the ideXlab platform.
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Dechlorination of polychlorinated biphenyl congeners by anaerobic microorganisms from river sediment.
Water environment research : a research publication of the Water Environment Federation, 2006Co-Authors: Bea-ven Chang, Tzu-chuan Chiu, S.y. YuanAbstract:The microbial Dechlorination of seven kinds of polychlorinated biphenyls (PCBs) by anaerobic microorganisms from river sediment was investigated. Dechlorination rates were found to be affected by the chlorine level of PCB congeners; Dechlorination rates decreased as chlorine levels increased. Dechlorination rates were fastest under methanogenic conditions and slowest under nitrate-reducing conditions. The addition of individual electron donors (acetate, pyruvate, and lactate) enhanced the Dechlorination of PCB congeners under methanogenic and sulfate-reducing conditions but delayed the Dechlorination of PCB congeners under nitrate-reducing conditions. PCB congener Dechlorination also was delayed by the addition of various polycyclic aromatic hydrocarbons (PAHs) under three reducing conditions and by surfactants, such as brij30, triton SN70, and triton N101. The results suggest that methanogen, sulfate-reducing bacteria, and nitrate-reducing bacteria all are involved in the Dechlorination of PCB congeners.
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Microbial Dechlorination of 2,4,6-trichlorophenol in anaerobic sewage sludge.
Journal of environmental science and health. Part. B Pesticides food contaminants and agricultural wastes, 1999Co-Authors: Bea-ven Chang, Chen-wei Chiang, S.y. YuanAbstract:Abstract The Dechlorination of 2,4,6‐trichlorophenol (TCP) in municipal sewage sludge with a chlorophenol (CP)‐adapted consortium was investigated. Results show that Dechlorination rates differed according to the source of the sludge samples used in the batch experiments. No significant differences in 2,4,6‐TCP Dechlorination were observed following treatment with inoculum at densities ranging from 10% to 50% (V/V), but a significant delay was noted at 5% (V/V) density. Overall, results show that the higher the 2,4,6‐TCP concentration, the slower the Dechlorination rate. The addition of acetate, lactate, pyruvate, vitamin B12 or manganese dioxide did not results in a significant change in 2,4,6‐TCP Dechlorination. Data collected from a bioreactor experiment revealed that pH 7.0 and a total solid concentration of 10 g/L were optimal for Dechlorination. Dechlorination rates decreased significantly at higher agitation speeds. 2,4,6‐TCP Dechlorination was enhanced under methanogenic conditions, but it was inh...
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Microbial Dechlorination of polychlorinated biphenyls in anaerobic sewage sludge.
Chemosphere, 1999Co-Authors: Bea-ven Chang, S. W. Chou, S.y. YuanAbstract:The potential of a chlorophenol (CP)-adapted consortium to dechlorinate polychlorinated biphenyls (PCBs) in sewage sludge was investigated. Results show that Dechlorination rates differed significantly depending on sludge source and PCB congener. Higher total solid concentrations in sewage sludge and higher concentrations of chlorine in PCB resulted in slower Dechlorination rates. No significant difference was found for 2,3,4,5-CB Dechlorination from pH 6.0 to pH 8.0; however, Dechlorination did not occur at pH 9.0 during a 41-day incubation period. Results show that at concentrations of 1 to 10 mg/L, the higher the PCB concentration, the faster the Dechlorination rate. In addition, Dechlorination rates were in the following order: methanogenic conditions > sulfate-reducing conditions > denitrifying conditions. The addition of acetate, lactate, pyruvate, and ferric chloride decreased lag times and enhanced Dechlorination; however, the addition of manganese dioxide had an inhibitory effect. Dechlorination rates were also enhanced by the addition of PCB congeners, including 2,3,4-CB, 2,3,4,5-CB and 2,3,4,5,6-CB in mixture. Overall results show that the CP-adapted consortium has the potential to enhance PCB Dechlorination. The optimal Dechlorination conditions presented in this paper may be used as a reference for feasibility studies of PCB removal from sludge.
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Dechlorination of polychlorinated biphenyls by an anaerobic mixed culture
Journal of Environmental Science and Health Part A, 1999Co-Authors: Bea-ven Chang, S. W. Chou, S.y. YuanAbstract:Abstract The reductive Dechlorination of polychlorinated biphenyls (PCBs) in enriched medium with an anaerobic chlorophenol (CP)‐adapted consortium was investigated in order to define the conditions which control PCB Dechlorination in naturally anaerobic environments. The fastest observed Dechlorination rates of 2, 3, 4‐CB or 2, 3, 4, 5 ‐CB (1 mg/L concentration) to the intermediate products dichlorobiphenyl or trichlorobiphenyl were 0.15 and 0.14 mg/L/day at 30°C and pH7.0. For PCB congeners with higher chlorine content (2, 2’, 4, 4’, 6, 6'‐CB, 2, 2’, 3, 4, 4’, 5, 5'‐CB), the Dechlorination rate dropped sharply to below 0.01 mg/L/day. The congeners 2, 2’, 3, 3’, 4, 4'‐CB and 2, 2’, 3, 3’, 4, 4’, 5, 5'‐CB were not dechlorinated to lower chlorinated congeners even after a 100‐day incubation period. The addition of electron donors did not enhance the Dechlorination rates for 2, 3, 4‐CB, 2, 3, 4, 5‐CB or 2, 2’, 4, 4’, 6, 6'‐CB. For these three congeners, Dechlorination was enhanced under methanogenic conditi...
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Dechlorination of pentachlorophenol in anaerobic sewage sludge
Chemosphere, 1998Co-Authors: Bea-ven Chang, Chen-wei Chiang, S.y. YuanAbstract:Abstract Dechlorination of pentachlorophenol (PCP) in municipal sewage sludge by a chlorophenols (CPs)-adapted consortium was investigated. Results of a batch experiment showed no significant differences in PCP Dechlorination following treatment with inoculum at densities ranging from 10% to 50%, but a significant delay following treatment with inoculum at 5% density. Results also show that the higher the PCP concentration, the slower the Dechlorination rate. PCP dechlorimation was not significantly altered by the addition of acetate, lactate, pyruvate, vitamin B 12 or manganese dioxide. Results from a bioreactor experiment show optimal pH for Dechlorination at 7.0 and optimal total solid concentration at 10 g/L. Dechlorination rates were also found to decrease significantly at higher agitation speeds. Finally, it was found that methanogenic conditions enhanced PCP Dechlorination, but denitrifying and sulfidogenic conditions inhibited the Dechlorination process.
Bea-ven Chang - One of the best experts on this subject based on the ideXlab platform.
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Dechlorination of polychlorinated biphenyl congeners by anaerobic microorganisms from river sediment.
Water environment research : a research publication of the Water Environment Federation, 2006Co-Authors: Bea-ven Chang, Tzu-chuan Chiu, S.y. YuanAbstract:The microbial Dechlorination of seven kinds of polychlorinated biphenyls (PCBs) by anaerobic microorganisms from river sediment was investigated. Dechlorination rates were found to be affected by the chlorine level of PCB congeners; Dechlorination rates decreased as chlorine levels increased. Dechlorination rates were fastest under methanogenic conditions and slowest under nitrate-reducing conditions. The addition of individual electron donors (acetate, pyruvate, and lactate) enhanced the Dechlorination of PCB congeners under methanogenic and sulfate-reducing conditions but delayed the Dechlorination of PCB congeners under nitrate-reducing conditions. PCB congener Dechlorination also was delayed by the addition of various polycyclic aromatic hydrocarbons (PAHs) under three reducing conditions and by surfactants, such as brij30, triton SN70, and triton N101. The results suggest that methanogen, sulfate-reducing bacteria, and nitrate-reducing bacteria all are involved in the Dechlorination of PCB congeners.
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Microbial Dechlorination of 2,4,6-trichlorophenol in anaerobic sewage sludge.
Journal of environmental science and health. Part. B Pesticides food contaminants and agricultural wastes, 1999Co-Authors: Bea-ven Chang, Chen-wei Chiang, S.y. YuanAbstract:Abstract The Dechlorination of 2,4,6‐trichlorophenol (TCP) in municipal sewage sludge with a chlorophenol (CP)‐adapted consortium was investigated. Results show that Dechlorination rates differed according to the source of the sludge samples used in the batch experiments. No significant differences in 2,4,6‐TCP Dechlorination were observed following treatment with inoculum at densities ranging from 10% to 50% (V/V), but a significant delay was noted at 5% (V/V) density. Overall, results show that the higher the 2,4,6‐TCP concentration, the slower the Dechlorination rate. The addition of acetate, lactate, pyruvate, vitamin B12 or manganese dioxide did not results in a significant change in 2,4,6‐TCP Dechlorination. Data collected from a bioreactor experiment revealed that pH 7.0 and a total solid concentration of 10 g/L were optimal for Dechlorination. Dechlorination rates decreased significantly at higher agitation speeds. 2,4,6‐TCP Dechlorination was enhanced under methanogenic conditions, but it was inh...
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Microbial Dechlorination of polychlorinated biphenyls in anaerobic sewage sludge.
Chemosphere, 1999Co-Authors: Bea-ven Chang, S. W. Chou, S.y. YuanAbstract:The potential of a chlorophenol (CP)-adapted consortium to dechlorinate polychlorinated biphenyls (PCBs) in sewage sludge was investigated. Results show that Dechlorination rates differed significantly depending on sludge source and PCB congener. Higher total solid concentrations in sewage sludge and higher concentrations of chlorine in PCB resulted in slower Dechlorination rates. No significant difference was found for 2,3,4,5-CB Dechlorination from pH 6.0 to pH 8.0; however, Dechlorination did not occur at pH 9.0 during a 41-day incubation period. Results show that at concentrations of 1 to 10 mg/L, the higher the PCB concentration, the faster the Dechlorination rate. In addition, Dechlorination rates were in the following order: methanogenic conditions > sulfate-reducing conditions > denitrifying conditions. The addition of acetate, lactate, pyruvate, and ferric chloride decreased lag times and enhanced Dechlorination; however, the addition of manganese dioxide had an inhibitory effect. Dechlorination rates were also enhanced by the addition of PCB congeners, including 2,3,4-CB, 2,3,4,5-CB and 2,3,4,5,6-CB in mixture. Overall results show that the CP-adapted consortium has the potential to enhance PCB Dechlorination. The optimal Dechlorination conditions presented in this paper may be used as a reference for feasibility studies of PCB removal from sludge.
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Dechlorination of polychlorinated biphenyls by an anaerobic mixed culture
Journal of Environmental Science and Health Part A, 1999Co-Authors: Bea-ven Chang, S. W. Chou, S.y. YuanAbstract:Abstract The reductive Dechlorination of polychlorinated biphenyls (PCBs) in enriched medium with an anaerobic chlorophenol (CP)‐adapted consortium was investigated in order to define the conditions which control PCB Dechlorination in naturally anaerobic environments. The fastest observed Dechlorination rates of 2, 3, 4‐CB or 2, 3, 4, 5 ‐CB (1 mg/L concentration) to the intermediate products dichlorobiphenyl or trichlorobiphenyl were 0.15 and 0.14 mg/L/day at 30°C and pH7.0. For PCB congeners with higher chlorine content (2, 2’, 4, 4’, 6, 6'‐CB, 2, 2’, 3, 4, 4’, 5, 5'‐CB), the Dechlorination rate dropped sharply to below 0.01 mg/L/day. The congeners 2, 2’, 3, 3’, 4, 4'‐CB and 2, 2’, 3, 3’, 4, 4’, 5, 5'‐CB were not dechlorinated to lower chlorinated congeners even after a 100‐day incubation period. The addition of electron donors did not enhance the Dechlorination rates for 2, 3, 4‐CB, 2, 3, 4, 5‐CB or 2, 2’, 4, 4’, 6, 6'‐CB. For these three congeners, Dechlorination was enhanced under methanogenic conditi...
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Dechlorination of pentachlorophenol in anaerobic sewage sludge
Chemosphere, 1998Co-Authors: Bea-ven Chang, Chen-wei Chiang, S.y. YuanAbstract:Abstract Dechlorination of pentachlorophenol (PCP) in municipal sewage sludge by a chlorophenols (CPs)-adapted consortium was investigated. Results of a batch experiment showed no significant differences in PCP Dechlorination following treatment with inoculum at densities ranging from 10% to 50%, but a significant delay following treatment with inoculum at 5% density. Results also show that the higher the PCP concentration, the slower the Dechlorination rate. PCP dechlorimation was not significantly altered by the addition of acetate, lactate, pyruvate, vitamin B 12 or manganese dioxide. Results from a bioreactor experiment show optimal pH for Dechlorination at 7.0 and optimal total solid concentration at 10 g/L. Dechlorination rates were also found to decrease significantly at higher agitation speeds. Finally, it was found that methanogenic conditions enhanced PCP Dechlorination, but denitrifying and sulfidogenic conditions inhibited the Dechlorination process.
G. Yull Rhee - One of the best experts on this subject based on the ideXlab platform.
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Effects of a rhamnolipid biosurfactant on the reductive Dechlorination of polychlorinated biphenyls by St. Lawrence River (North America) microorganisms
Environmental Toxicology and Chemistry, 2004Co-Authors: Young-cheol Cho, Ellen B. Ostrofsky, G. Yull RheeAbstract:The effect of a rhamnolipid biosurfactant on the reductive Dechlorination of polychlorinated biphenyls was investigated with the use of clean sediments spiked with Aroclor 1248. The surfactant was added to the contaminated sediments at four different concentrations (5, 10, 25, and 50 microg/g sediment [ppm] on a sediment dry wt basis), and Dechlorination was followed over a 40-week period. The rate of overall Dechlorination was enhanced at the three highest concentrations. Dechlorination at the lowest concentration (5 ppm) was not different from that in surfactant-free sediments. On a congener basis, enhanced Dechlorination was mostly found in the congeners that have high threshold concentrations for Dechlorination. These congeners are characterized by an initial increase in concentration before Dechlorination starts. At the three highest biosurfactant concentrations, this initial concentration increase was absent or dramatically reduced. Therefore, the enhancement in Dechlorination appears to be caused by an increase in bioavailability at high surfactant concentrations. The biosurfactant also reduced the lag time before Dechlorination began in these congeners. Among those congeners that have low threshold concentrations, Dechlorination enhancement was found only in two peaks. For these two, there was no lag period, either with or without the rhamnolipids. The maximum level of Dechlorination and the congener pattern of final Dechlorination products were identical, regardless of biosurfactant concentration.
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Enhancement of microbial PCB Dechlorination by chlorobenzoates, chlorophenols and chlorobenzenes.
FEMS microbiology ecology, 2002Co-Authors: Young-cheol Cho, Ellen B. Ostrofsky, Roger C. Sokol, Robert C. Frohnhoefer, G. Yull RheeAbstract:We investigated the effects of chlorobenzoates (3-, 2,3-, 2,4-, 2,5-, 2,3,5- and 2,4,6-chlorobenzoate), chlorophenols (2,3-, 3,4-, 2,5-, 2,3,6- and penta-chlorophenol), and chlorobenzenes (1,2-, 1,2,3-, 1,2,4- and penta-chlorobenzene) on polychlorinated biphenyl (PCB) Dechlorination and on the enrichment of PCB-dechlorinating microorganisms. When the natural microbial populations eluted from St. Lawrence River sediments were enriched with each of the 15 haloaromatic compounds (HACs) in PCB-free sediments, PCB-dechlorinating microorganisms were found in all but pentachlorophenol-amended sediments. Similarly, dechlorinating microorganisms were also found in PCB-spiked sediments amended with all HACs, except for those with pentachlorophenol. In HAC-amended PCB sediments there was a long lag in PCB Dechlorination until the HACs were reduced to a plateau level. Despite this lag, once PCB Dechlorination started it was faster in the HAC-amended sediments compared to the unamended controls. The overall extent of PCB Dechlorination was significantly enhanced by all HACs except pentachlorophenol and pentachlorobenzene, but the extent as well as the pattern of the enhancement varied. Of the 13 effective HACs, six (2,3-, 2,4- and 2,4,6-chlorobenzoates; 3,4- and 2,3,6-chlorophenols; and 1,2,3-chlorobenzene) enhanced only meta-Dechlorination, whereas five (3-chlorobenzoate; 2,3- and 2,5-chlorophenols; and 1,2- and 1,2,4-chlorobenzenes) increased both meta- and para-Dechlorination, and two (2,5- and 2,3,5-chlorobenzoates) promoted overall, substitution non-specific Dechlorination. When the maximum extent of Dechlorination was plotted against the highest number of PCB-dechlorinating microorganisms for each HAC, there was a linear relationship (P
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Microbial PCB Dechlorination in dredged sediments and the effect of moisture.
Chemosphere, 2001Co-Authors: Young-cheol Cho, Roger C. Sokol, Charlotte M. Bethoney, O.-seob Kwon, G. Yull RheeAbstract:Evidence of reductive Dechlorination of polychlorinated biphenyls (PCBs) in sediments was investigated in Hudson River sediments dredged and encapsulated in 1978 at Moreau, NY. The effect of different moisture contents in dredged sediments on Dechlorination and dechlorinating microorganisms was also determined using PCB-spiked sediments in which the moisture level was adjusted by simulating a dewatering process. The congener pattern of PCBs indicated that the Dechlorination in the dredged sediments was far less advanced than that in the river sediments collected from the general area of the dredged site (Ft. Edward site). Dechlorination in encapsulated sediments at the Moreau site appeared to have stopped soon after dredging. When microorganisms eluted from the encapsulated sediments were inoculated in clean sediments spiked with Aroclor 1242, an extensive Dechlorination was observed, indicating that the encapsulated sediments still harbored dechlorinating microorganisms. However, the same inoculum failed to further dechlorinate residual congeners in the dredged sediments. On the other hand, an inoculum obtained in 1990 from the dredged site in the Hudson River dechlorinated the residual congeners further. In simulated dredged sediments, the maximum level of Dechlorination was lower at reduced moisture contents. The population size of dechlorinating microorganisms, as determined by the most probable number (MPN) technique, was also smaller at the lower moisture levels. There was a significant correlation between the maximum extent of Dechlorination and the specific death rate of dechlorinating populations. These results indicate that the underlying mechanism of the moisture-dependent maximum Dechlorination is the moisture-dependence of the death rate of dechlorinating microorganisms.
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An investigation of factors limiting the reductive Dechlorination of polychlorinated biphenyls
Environmental Toxicology and Chemistry, 1996Co-Authors: Xia Liu, Charlotte M. Bethoney, Roger C. Sokol, O.-seob Kwon, G. Yull RheeAbstract:A study was conducted to determine whether the apparent limitation of Dechlorination of Aroclor 1248 was due to bioavailability of polychlorinated biphenyls (PCBs) or an accumulation of metabolic products. After 15 weeks of laboratory incubation, sediment microorganisms from the St. Lawrence River reduced the total number of chlorines in Aroclor 1248-spiked sediments by 33%. However, Dechlorination apparently leveled off with a significant number of meta- and para-chlorines still remaining, showing no further change out to 30 weeks. When these sediments were incubated an additional 18 weeks with either fresh medium or the original supernatant, no additional Dechlorination was found in either treatment. Similarly, Dechlorination was not inhibited in freshly spiked Aroclor 1248 sediment slurries made with the old supernatant. Addition of the nonionic surfactant Tween 20, at a concentration below the critical micelle concentration that increased PCB desorption, also failed to enhance Dechlorination of the plateau sediments. The extent and final congener pattern in all treatments were nearly identical. Therefore, the termination of Dechlorination at the plateau level was not due to PCB bioavailability or accumulation of inhibitory metabolic products. These results strongly suggest that the cessation of Dechlorination at the plateau was due to the accumulation of daughter congeners with chlorine substitution patterns that were not amenable to further Dechlorination by the present microbial consortium.
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Effect of PCB concentration on reductive Dechlorination and Dechlorination potential in natural sediments
Water Research, 1995Co-Authors: Roger C. Sokol, Charlotte M. Bethoney, G. Yull RheeAbstract:Abstract The effect of PCB concentration on microbial reductive Dechlorination was examined using two individual congeners, 2,3,4- and 2,3,4,2′,4′,5′-chlorobiphenyl (CBP), at four concentrations ranging from 4 to 35 ppm. Dechlorination potential in PCB-contaminated river sediments was also determined as the length of the lag period in a single congener Dechlorination assay using contaminated sediments as inocula. Dechlorination of 2,3,4-CBP was concentration-dependent and occurred at all concentrations by 14 weeks and the residual concentration of the parent congener appeared to be the same regardless of the initial concentrations. By contrast, 2,3,4,2′,4′,5′-CBP showed Dechlorination only at the highest concentration after 23 weeks. The concentration dependence and the lag period thus were congener-specific. Dechlorination potential, measured as the length of the lag before Dechlorination of 3,4,5-CBP, seemed to be longer with inocula prepared from sediments with lower ambient PCB concentrations. Taken together, these results imply that in situ Dechlorination may not be able to occur in areas with low ambient PCB levels because both Dechlorination rate and Dechlorination potential are concentration-dependent. In sediments which are no longer submerged, dechlorinating activity was not found.
Donna L Bedard - One of the best experts on this subject based on the ideXlab platform.
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A case study for microbial biodegradation: anaerobic bacterial reductive Dechlorination of polychlorinated biphenyls-from sediment to defined medium.
Annual Review of Microbiology, 2008Co-Authors: Donna L BedardAbstract:The history of anaerobic microbial polychlorinated biphenyl (PCB) Dechlorination is traced over 20 years using a case study of PCB Dechlorination in the Housatonic River (Massachusetts) as an example. The history progresses from the characterization of the PCBs in the sediment, to cultivation in sediment microcosms, to the identification of four distinct types of PCB Dechlorination, to a successful field test, to the cultivation in defined medium of the organisms responsible for extensive Dechlorination of Aroclor 1260, and finally to the identification of a Dehalococcoides population that links its growth to the Dechlorination of Aroclor 1260. Other PCB dechlorinators have also been identified. Two bacterial strains, o-17 and DF-1, that link their growth to the Dechlorination of several PCB congeners belong to a novel clade of putative dechlorinating bacteria within the phylum Chloroflexi. Dehalococcoides ethenogenes strain 195 also dechlorinates several PCB congeners when grown on chlorinated ethenes. E...
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Use of Halogenated Benzoates and Other Halogenated Aromatic Compounds To Stimulate the Microbial Dechlorination of PCBs
Environmental Science & Technology, 1999Co-Authors: Kim A Deweerd, Donna L BedardAbstract:In this study, the authors tested the ability of halogenated benzoates and other halogenated aromatic compounds to prime PCB Dechlorination in the same sediments. They found that none of the fluorinated or chlorinated benzoates primed PCB Dechlorination, but several brominated and iodinated benzoates initiated this activity. Of the halogenated benzoates tested, 4-bromobenzoate, 4-iodobenzoate, and 2,5-dibromobenzoate primed the most extensive PCB Dechlorination, decreasing the hexa- through nonachlorobiphenyl fraction of Aroclor 1260 by 40--70%, 10--50%, and 10--50%, respectively. None of the halogenated benzoates were as effective at priming PCB Dechlorination as 2,6-dibromobiphenyl, which primed a 60--80% decrease of the hexa- through nonachlorobiphenyl fraction of Aroclor 1260. Several other brominated aromatic compounds were also tested for their ability to prime PCB Dechlorination. Monobrominated isomers of acetophenone, phenol, or toluene did not prime PCB Dechlorination, but all monobrominated isomers of benzonitrile, 2-bromo-, 4-bromo-, and 2,5-dibromonitrobenzene, 4-bromobenzamide, 4-bromobenzophenone, 4-bromobenzoic hydrazide, 4-bromobenzoic methyl ester, and 2,5-dibromobenzene sulfonate primed PCB Dechlorination in Housatonic River sediments. All of the compounds primed PCB Dechlorination Process N (primarily flanked meta Dechlorination) except 4-bromonitrobenzene, which primed Dechlorination Process P (flanked para Dechlorination). These results indicate that halogenated aromatic compounds that are not structural analogues to PCBs can prime PCB Dechlorination.
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temperature determines the pattern of anaerobic microbial Dechlorination of aroclor 1260 primed by 2 3 4 6 tetrachlorobiphenyl in woods pond sediment
Applied and Environmental Microbiology, 1997Co-Authors: Qingzhong Wu, Donna L Bedard, Juergen WiegelAbstract:Reductive Dechlorination of the Aroclor 1260 residue in Woods Pond (Lenox, Mass.) sediment samples was investigated for a year at incubation temperatures from 4 to 66 degrees C. Sediment slurries were incubated anaerobically with and without 2,3,4,6-tetrachlorobiphenyl (2346-CB; 350 microM) as a primer for Dechlorination of the Aroclor 1260 residue. Dechlorination of the Aroclor residue occurred only in live samples primed with 2346-CB and only at 8 to 34 degrees C and 50 to 60 degrees C. The extent and pattern of polychlorinated biphenyl (PCB) Dechlorination were temperature dependent. At 8 to 34 degrees C, the Dechlorination resulted in 28 to 65% decreases of the hexathrough nonachlorobiphenyls and corresponding increases in the tri- and tetrachlorobiphenyls. At 12 to 30 degrees C, 30 to 40% of the hexa- through nonachlorobiphenyls were dechlorinated in just 3 months. The optimal temperature for overall chlorine removal was 20 to 27 degrees C. We observed four different microbial Dechlorination processes with different but partially overlapping temperature ranges, i.e., Process N (flanked meta Dechlorination) at 8 to 30 degrees C, Process P (flanked para Dechlorination) at 12 to 34 degrees C, Process LP (unflanked para Dechlorination) at 18 to 30 degrees C, and Process T (a very restricted meta Dechlorination of specific hepta- and octachlorobiphenyls) at 50 to 60 degrees C. These temperature ranges should aid in the development of strategies for the enrichment and isolation of the microorganisms responsible for each Dechlorination process. The incubation temperature determined the relative dominance of the four PCB Dechlorination processes and the extent and products of Dechlorination. Hence, understanding the effects of temperature on PCB Dechlorination at contaminated sites should assist in predicting the environmental fate of PCBs or planning bioremediation strategies at those sites.
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temperature determines the pattern of anaerobic microbial Dechlorination of aroclor 1260 primed by 2 3 4 6 tetrachlorobiphenyl in
1997Co-Authors: Qingzhong Wu, Donna L Bedard, Juergen WiegelAbstract:Reductive Dechlorination of the Aroclor 1260 residue in Woods Pond (Lenox, Mass.) sediment samples was investigated for a year at incubation temperatures from 4 to 66°C. Sediment slurries were incubated anaerobically with and without 2,3,4,6-tetrachlorobiphenyl (2346-CB; 350 mM) as a primer for Dechlorination of the Aroclor 1260 residue. Dechlorination of the Aroclor residue occurred only in live samples primed with 2346-CB and only at 8 to 34°C and 50 to 60°C. The extent and pattern of polychlorinated biphenyl (PCB) Dechlorination were temperature dependent. At 8 to 34°C, the Dechlorination resulted in 28 to 65% decreases of the hexathrough nonachlorobiphenyls and corresponding increases in the tri- and tetrachlorobiphenyls. At 12 to 30°C, 30 to 40% of the hexa- through nonachlorobiphenyls were dechlorinated in just 3 months. The optimal temperature for overall chlorine removal was 20 to 27°C. We observed four different microbial Dechlorination processes with different but partially overlapping temperature ranges, i.e., Process N (flanked meta Dechlorination) at 8 to 30°C, Process P (flanked para Dechlorination) at 12 to 34°C, Process LP (unflanked para Dechlorination) at 18 to 30°C, and Process T (a very restricted meta Dechlorination of specific hepta- and octachlorobiphenyls) at 50 to 60°C. These temperature ranges should aid in the development of strategies for the enrichment and isolation of the microorganisms responsible for each Dechlorination process. The incubation temperature determined the relative dominance of the four PCB Dechlorination processes and the extent and products of Dechlorination. Hence, understanding the effects of temperature on PCB Dechlorination at contaminated sites should assist in predicting the environmental fate of PCBs or planning bioremediation strategies at those sites.
Roger C. Sokol - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of microbial PCB Dechlorination by chlorobenzoates, chlorophenols and chlorobenzenes.
FEMS microbiology ecology, 2002Co-Authors: Young-cheol Cho, Ellen B. Ostrofsky, Roger C. Sokol, Robert C. Frohnhoefer, G. Yull RheeAbstract:We investigated the effects of chlorobenzoates (3-, 2,3-, 2,4-, 2,5-, 2,3,5- and 2,4,6-chlorobenzoate), chlorophenols (2,3-, 3,4-, 2,5-, 2,3,6- and penta-chlorophenol), and chlorobenzenes (1,2-, 1,2,3-, 1,2,4- and penta-chlorobenzene) on polychlorinated biphenyl (PCB) Dechlorination and on the enrichment of PCB-dechlorinating microorganisms. When the natural microbial populations eluted from St. Lawrence River sediments were enriched with each of the 15 haloaromatic compounds (HACs) in PCB-free sediments, PCB-dechlorinating microorganisms were found in all but pentachlorophenol-amended sediments. Similarly, dechlorinating microorganisms were also found in PCB-spiked sediments amended with all HACs, except for those with pentachlorophenol. In HAC-amended PCB sediments there was a long lag in PCB Dechlorination until the HACs were reduced to a plateau level. Despite this lag, once PCB Dechlorination started it was faster in the HAC-amended sediments compared to the unamended controls. The overall extent of PCB Dechlorination was significantly enhanced by all HACs except pentachlorophenol and pentachlorobenzene, but the extent as well as the pattern of the enhancement varied. Of the 13 effective HACs, six (2,3-, 2,4- and 2,4,6-chlorobenzoates; 3,4- and 2,3,6-chlorophenols; and 1,2,3-chlorobenzene) enhanced only meta-Dechlorination, whereas five (3-chlorobenzoate; 2,3- and 2,5-chlorophenols; and 1,2- and 1,2,4-chlorobenzenes) increased both meta- and para-Dechlorination, and two (2,5- and 2,3,5-chlorobenzoates) promoted overall, substitution non-specific Dechlorination. When the maximum extent of Dechlorination was plotted against the highest number of PCB-dechlorinating microorganisms for each HAC, there was a linear relationship (P
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Microbial PCB Dechlorination in dredged sediments and the effect of moisture.
Chemosphere, 2001Co-Authors: Young-cheol Cho, Roger C. Sokol, Charlotte M. Bethoney, O.-seob Kwon, G. Yull RheeAbstract:Evidence of reductive Dechlorination of polychlorinated biphenyls (PCBs) in sediments was investigated in Hudson River sediments dredged and encapsulated in 1978 at Moreau, NY. The effect of different moisture contents in dredged sediments on Dechlorination and dechlorinating microorganisms was also determined using PCB-spiked sediments in which the moisture level was adjusted by simulating a dewatering process. The congener pattern of PCBs indicated that the Dechlorination in the dredged sediments was far less advanced than that in the river sediments collected from the general area of the dredged site (Ft. Edward site). Dechlorination in encapsulated sediments at the Moreau site appeared to have stopped soon after dredging. When microorganisms eluted from the encapsulated sediments were inoculated in clean sediments spiked with Aroclor 1242, an extensive Dechlorination was observed, indicating that the encapsulated sediments still harbored dechlorinating microorganisms. However, the same inoculum failed to further dechlorinate residual congeners in the dredged sediments. On the other hand, an inoculum obtained in 1990 from the dredged site in the Hudson River dechlorinated the residual congeners further. In simulated dredged sediments, the maximum level of Dechlorination was lower at reduced moisture contents. The population size of dechlorinating microorganisms, as determined by the most probable number (MPN) technique, was also smaller at the lower moisture levels. There was a significant correlation between the maximum extent of Dechlorination and the specific death rate of dechlorinating populations. These results indicate that the underlying mechanism of the moisture-dependent maximum Dechlorination is the moisture-dependence of the death rate of dechlorinating microorganisms.
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An investigation of factors limiting the reductive Dechlorination of polychlorinated biphenyls
Environmental Toxicology and Chemistry, 1996Co-Authors: Xia Liu, Charlotte M. Bethoney, Roger C. Sokol, O.-seob Kwon, G. Yull RheeAbstract:A study was conducted to determine whether the apparent limitation of Dechlorination of Aroclor 1248 was due to bioavailability of polychlorinated biphenyls (PCBs) or an accumulation of metabolic products. After 15 weeks of laboratory incubation, sediment microorganisms from the St. Lawrence River reduced the total number of chlorines in Aroclor 1248-spiked sediments by 33%. However, Dechlorination apparently leveled off with a significant number of meta- and para-chlorines still remaining, showing no further change out to 30 weeks. When these sediments were incubated an additional 18 weeks with either fresh medium or the original supernatant, no additional Dechlorination was found in either treatment. Similarly, Dechlorination was not inhibited in freshly spiked Aroclor 1248 sediment slurries made with the old supernatant. Addition of the nonionic surfactant Tween 20, at a concentration below the critical micelle concentration that increased PCB desorption, also failed to enhance Dechlorination of the plateau sediments. The extent and final congener pattern in all treatments were nearly identical. Therefore, the termination of Dechlorination at the plateau level was not due to PCB bioavailability or accumulation of inhibitory metabolic products. These results strongly suggest that the cessation of Dechlorination at the plateau was due to the accumulation of daughter congeners with chlorine substitution patterns that were not amenable to further Dechlorination by the present microbial consortium.
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Effect of PCB concentration on reductive Dechlorination and Dechlorination potential in natural sediments
Water Research, 1995Co-Authors: Roger C. Sokol, Charlotte M. Bethoney, G. Yull RheeAbstract:Abstract The effect of PCB concentration on microbial reductive Dechlorination was examined using two individual congeners, 2,3,4- and 2,3,4,2′,4′,5′-chlorobiphenyl (CBP), at four concentrations ranging from 4 to 35 ppm. Dechlorination potential in PCB-contaminated river sediments was also determined as the length of the lag period in a single congener Dechlorination assay using contaminated sediments as inocula. Dechlorination of 2,3,4-CBP was concentration-dependent and occurred at all concentrations by 14 weeks and the residual concentration of the parent congener appeared to be the same regardless of the initial concentrations. By contrast, 2,3,4,2′,4′,5′-CBP showed Dechlorination only at the highest concentration after 23 weeks. The concentration dependence and the lag period thus were congener-specific. Dechlorination potential, measured as the length of the lag before Dechlorination of 3,4,5-CBP, seemed to be longer with inocula prepared from sediments with lower ambient PCB concentrations. Taken together, these results imply that in situ Dechlorination may not be able to occur in areas with low ambient PCB levels because both Dechlorination rate and Dechlorination potential are concentration-dependent. In sediments which are no longer submerged, dechlorinating activity was not found.
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Anaerobic Dechlorination of aroclor 1242 as affected by some environmental conditions
Environmental Toxicology and Chemistry, 1993Co-Authors: G. Yull Rhee, Roger C. Sokol, Brian Bush, C.m. Bethoney, A. DenucciAbstract:The effect of electron acceptors and biphenyl on reductive Dechlorination was investigated using the commercial polychlorinated biphenyl mixture Aroclor 1242 and sediment microorganisms from the Hudson River. Polychlorinated biphenyl- (PCB-) free sediments spiked with the Aroclor at 700 μg/g and anaerobically incubated for six months, with and without biphenyl enrichment, showed that Dechlorination was most advanced with CO2 without biphenyl enrichment. A small amount of methane was detected. However, methane production per se was not essential for Dechlorination, because addition of the inhibitor of methane production, 2-bromoethane sulfonate, did not affect Dechlorination. On the other hand, Dechlorination was inhibited partly by sulfate and completely by nitrate. Biphenyl enrichment initially inhibited Dechlorination under both methanogenic and sulfidogenic conditions.
