• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.147-152
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• 2004

Aerobic cometabolism of cis-1,2-dichloroethylene (c-DCE) and c-DCE epoxide by a butane-grown mixed culture was evaluated. Transformation of c-DCE resulted in the concomitant generation of c-DCE epoxide. Chloride release studies showed nearly complete oxidative dechlorination of c-DCE (approximately 75%). Mass spectrometry confirmed tile presence of a compound with mass-to-charge-fragment ratios of 112, 83, 48, and 35. The values are in agreement with the spectra of a chemically synthesized c-DCE epoxide. Some evidences indicating the involvement of the monooxygenase in the transformation of c-DCE epoxide are: 1) $O_2$ requirement for c-DCE transformation and butane degradation; 2) butane inhibition on c-DCE transformation and vice versa; 3) the inactivation of c-DCE and c-DCE epoxide transformations by acetylene (a known monooxygenase inactivator); and 4) tire inhibition of c-DCE epoxide transformation by c-DCE.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.553-556
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• 2006

A cis-1,2-dichloroethylene (cis-DCE)-degrading anaerobic bacterium, Clostridium sp. strain KYT-1, was isolated from a sediment sample collected from a landfill site in Nanji-do, Seoul, Korea. The KYT-1 strain is a gram-positive, endospore-forming, motile, rod-shaped anaerobic bacterium, of approximately $2.5{\sim}3.0\;{\mu}m$ in length. The degradation of cis-DCE is closely related with the growth of the KYT-1 strain, and it was stopped when the growth of the KYT-1 strain became constant. Although the pathway of cis-DCE degradation by strain KYT-1 remains to be further elucidated, no accumulation of the harmful intermediate, vinyl chloride (VC), was observed during anaerobic cis-DCE degradation. Strain KYT-1 proved able to degrade a variety of volatile organic compounds, including VC, isomers of DCE (1,1-dichloroethylene, trans-1,2-dichloroethylene, and cis-DCE), trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane. Strain KYT-1 degraded cis-DCE at a range of temperatures from $15\;to\;37^{\circ}C$, with an optimum at $30^{\circ}C$, and at a pH range of 5.5 to 8.5, with an optimum at 7.0.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.440-444
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• 2003

A new approach for ground water treatment combines a permeable Fe(0) barrier to breakdown higher chlorinated solvents like PCE and TCE with a down gradient aerobic biological treatment system to biotransform less chlorinated solvents, such as DCE and vinyl chloride (VC). The expected bacterial performance down gradient of an Fe(0) barrier was evaluated through laboratory batch experiments with a toluene-degrading mixed culture that cometabolically transforms cis-1,2-DCE and VC. The amount of cis-1,2-DCE (initially at 2,000 ppb) and VC (initially at 2,000 ppb) transformed was controlled by the initial toluene(20,000 ppb) concentration. VC was removed much more effectively than Cis-1,2-DCE, and a higher toluene concentration in comparison to the co-substrate concentrations was needed for complete co-substrate removal. Overall, the coupling of an Fe(0) barrier and subsequent biodegradation appears feasible for remediation of complex mixtures of chlorinated solvents and petroleum hydrocarbons in groundwater.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.366-372
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• 2003

The production of microbiologically enriched cultures that degrade cis- 1,2-dichloroethylene(DCE) under anaerobic conditions was investigated. Among 80 environmental samples, 19 displayed significant degradation of $10{\mu}M$ cis-DCE during 1 month of anaerobic incubation, and one sediment sample collected at a landfill area (Nanji-do, Seoul, Korea) showed the greatest degradation ($94\%$). When this sediment culture was subcultured repeatedly, the ability to degrade cis-DCE gradually decreased. However, under Fe(III)-reducing conditions, cis-DCE degradation by the subculture was found to be maintained effectively. In the Fe(III)-reducing subculture, vinyl chloride (VC) was also degraded at the same extent as cis-DCE No accumulation of VC during the cis-DCE degradation was observed. Thus, Fe(III)-reducing microbes might be involved in the anaerobic degradation of the chlorinated ethenes. However, the subcultures established with Fe(III) could function even in the absence of Fe(III), showing that the degradation of cis-DCE and VC was not directly coupled with the Fe(III) reduction. Consequently, the two series of enrichment cultures could not be obtained that degrade both cis-DCE and VC in the presence or absence of Fe(III). Considering the lack of VC accumulation, both cultures reported herein may involve interesting mechanism(s) for the microbial remediation of environments contaminated with chlorinated ethenes. A number of fermentative reducers (microbes) which are known to reduce Fe(III) during their anaerobic growth are potential candidates involved in cir-DCE degradation in the presence and absence of Fe(III).

• Journal of Soil and Groundwater Environment
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• v.11 no.2
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• pp.68-76
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• 2006

Anaerobic reductive dechlorination of tetrachloroethylene (PCE) to ethylene was investigated by performing laboratory experiments using semi-continuous flow two-in-series soil columns. The columns were packed with soils obtained from TCE-contaminated site in Korea. Site ground water containing lactate (as electron donor and/or carbon source) and PCE was pumped into the soil columns. During the first operation with a period of 50 days, injected mass ratio of lactate and PCE was 620:1 and incomplete reductive dechlorination of PCE to cis-DCE was observed in the columns. However, complete dechlorination of PCE to ethylene was observed when the mass ratio increased to 5,050:1 in the second operation, suggesting that the electron donor might be limited during the first operation period. Dechlorination rate of PCE to cis-DCE was $0.62{\sim}1.94\;{\mu}mol$ PCE/L pore volume/d and $2.76\;{\mu}mol$ cis-DCE/ L pore volume/d for that for cis-DCE to ethylene, resulting that net dechlorination rate in the system was 1.43 umol PCE/L pore volume/d. During the degradation of cis-DCE to ethylene, the concentration of hydrogen in column groundwater was $22{\sim}29\;mM$ and $10{\sim}64\;mM$ for the degradation of PCE to cis-DCE. These positive results indicate that the TCE-contaminated groundwater investigated in this study could be remediated through in-situ biological anaerobic reductive dechlorination processes.

• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.53-59
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• 2012

This study investigated characteristics of decomposition of tetrabutoxysilane (TBOS) as a slow release substrate (SRS) and on effect of TBOS decompostion compounds (acetate and butylate) for anaerobic dechlorination of trichloroethylene (TCE). In the batch experiment, TCE, cis-dichloroethene (cis-DCE), 1-butanol and TBOS were analysed by GC/FID and acetate and butylate were measured by HPLC. 1M of TBOS transferred and accumulated 4M of 1-butanol by abiotically hydrolysis reaction. The hydrolysis rate was in a range of 0.186 ${\mu}M/day$. On other hand, 1-butanol fermented to butyrate and acetate with indigenous culture from natural sediments. This results showed that TBOS could be used a slow release substrate in the natural sites. The dechlorinated potential of TCE with acetate and butyrate was increased with a decreasing initial TCE concentrations. In addition, first order coefficients of dechlorination with acetate as electron donor was higher then that with butyrate. It is because that dechlorination of Geobacter lovleyi was affected by substrate affinity, biodegradability and microbial acclimation on various substrates. However, dechlorinated potential of Geobacter lovleyi was decreased with accumulation cis-DCE in the anaerobic decholoronation process. The overall results indicated that SRS with Geobacter lovleyi might be a promising material for enhancing dechlorination of TCE on natural site and cis-DCE should be treated by ZVI as reductive material or by coexisting other dechlorinated bacteria.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.454-457
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• 2003

A new approach for groundwater treatment combines a permeable Fe(0) barrier to breakdown higher chlorinated solvents like PCE and TCE with a downgradient aerobic biological treatment system to biotransform less chlorinated solvents, such as DCE and vinyl chloride (VC). The expected bacterial performance downgradient of an Fe(0) barrier was evaluated through laboratory batch experiments with a toluene-degrading mixed culture that cometabolically transforms cis-1,2-DCE and VC. The amount of cis-1,2-DCE (initially at 2,000 ppb) and VC (initially at 2,000 ppb) transformed was controlled by the initial toluene (20,000 ppb) concentration. VC was removed much more effectively than Cis-1,2-DCE, and a higher toluene concentration in comparison to the co-substrate concentrations was needed for complete co-substrate removal. Overall, the coupling of an Fe(0) barrier and subsequent biodegradation appears feasible for remediation of complex mixtures of chlorinated solvents and petroleum hydrocarbons in groundwater

• Membrane and Water Treatment
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• v.13 no.2
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• pp.85-95
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• 2022

Tetrachloroethylene (PCE) and trichloroethylene (TCE), critical pollutants to human health and groundwater ecosystems, are managed by groundwater quality standards (GQS) in South Korea. However, there are no GQSs for their by-products, such as cis-dichloroethylene (DCE) and vinyl chloride (VC) produced through the dechlorination process of PCE and TCE. Therefore, in this study, we monitored PCE, TCE, cis-DCE, and VC in 111 national groundwater wells for three years (2016 to 2018) to evaluate their distributions, a biological dechlorination possibility, and human risk assessment. The detection frequency of them was 30.2% for PCE, 45.1% for TCE, 43.9% for cis-DCE and 13.4% for VC. The four chlorinated compounds were commonly detected in 21 out of 111 wells. In the results of statistical analysis with 21 wells data, DO and ORP also had a negative correlation with four organic chlorinated compounds, while EC and sulfate has a positive correlation with the compounds. This indicates that the 21 wells were relatively met with suitable environments for a biological dechlorination reaction compared to the other wells. Finally, cis-DCE had a non-carcinogenic risk of 10^-1 and the carcinogenic risk of VC was 10^-6 or higher. Through this study, the distribution status of the four chlorinated compounds in groundwater in South Korea and the necessity of preparing plans to manage cis-DCE and VC were confirmed.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.332-336
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• 2004

An anaerobic PCE(tetrachloroethylene) dechlorinating bacterial culture from a landfill soil was enriched and characterized. The enrichment culture could dechlorinate 60$\mu$mol/$m\ell$ of PCE during a month of incubation and cis-DCE(cis-dichloroethylene) was observed as a main product of PCE dechlorination. Microbial analysis of the dechlorinating enrichment culture by rising PCR-DGGE (Polymerase chain reaction-Denaturing gradient gel electrophoresis) method showed that at least three microorganisms were related to the anaerobic PCE dechlorination.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.2
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• pp.55-65
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• 2003

The combined effect of bioaugmentation of dechlorinating bacterial cultures and addition of iron powder($Fe^0$ on reductive dechlorination of tetrachloroethylene(PCE) and other chlorinated ethylenes in a artificially contaminated soil slurry(60micromoles PCE/kg soil). Two different anaerobic bacterial cultures, a pure bacterial culture of Desulfitobacterium sp. strain Y-51 capable of dechlorinating PCE to cis-1,2-dechloroethylene(cis-DCE) and the other enrichment culture PE-1 capable of dechlorinating PCE completely to ethylene, were used for the bioaugmentation test. Both treatments introduced with the strain Y-51 and PE-1 culture (3mg dry cell weight/kg soil) showed conversion of PCE to cis-DCE within 40days. The treatments added with $Fe^0$(0.1-1.0%) alone to the soil slurry resulted in extended PCE dechlorination to ethylene and ethane and the dechlorination rate depended on the amount of $Fe^0$ added. The combined use of the bacterial cultures with $Fe^0$(0.1-1.0%)) showed the higher PCE dechlorination rate than the separated application and the pattern of PCE dechlorination and end-product formation was different from those of the separated application. When 0.1% of $Fe^0$ was added with the cultures, the treatments with the strain Y-51 and $Fe^0$ resulted in cis-DCE accumulation from PCE dechlorination, but the treatment with the enrichment culture and $Fe^0$ showed the more extended dechlorination via cis-DCE. These results suggested that the combined application of and the bactrial culture, specially the complete dechlorinating enrichment culture, is practically effective for bioremediation of PCE contaminated soil.