• Journal of Environmental Science International
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• v.16 no.10
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• pp.1147-1155
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• 2007

The applicability of in situ biobarrier or microbial filter technology for the remediation of groundwater contaminated with chlorinated solvent was investigated through column study. In this study, the effect of packing materials on the reductive dechlorination of PCE was investigated using Canadian peat, Pahokee peat, peat moss and vermicompost (or worm casting) as a biobarrier medium. Optimal conditions previously determined from a batch microcosm study was applied in this column study. Lactate/benzoate was amended as electron donors to stimulate reductive dechlorination of PCE. Hydraulic conductivity was approximately $6{\times}10^{-5}-8{\times}10^{-5}\;cm/sec$ and no difference was found among the packing materials. The transport and dispersion coefficients determined from the curve-fitting of the breakthrough curves of $Br^-$ using CXTFIT 2.1 showed no difference between single-region and two-region models. The reductive dechlorination of PCE was efficiently occurred in all columns. Among the columns, especially the column packed with vermicompost exhibited the highest reductive dechlorination efficiency. The results of this study showed the promising potential of in situ biobarrier technology using peat and vermicompost for the remediation of groundwater contaminated with chlorinated solvents.

• Korean Journal of Environmental Biology
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• v.17 no.2
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• pp.129-138
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• 1999

Chlorinated aromatic compounds are one of the largest groups of environmental pollutants as a result of world-wide distribution by using them as herbicides, insecticides, fungicides, solvents, hydraulic and heat transfer fluids, plasticizers, and intermediates for chemical synthesis. Because of their toxicity, persistence, and bioaccumulation, the compounds contaminated ubiquitously in the biosphere has attracted public concerns in terms of serious influences to wild lives and a human being, such as carcinogenicity, mutagenicity, and disturbance in endocrine systems. The biological recalcitrance of the compounds is caused by the number, type, and position of the chlorine substituents as well as by their aromatic structures. In general, the carbon-halogen bonds increase the recalcitrance by increasing electronegativity of the substituent, so that the dechlorination of the compounds is focused as an important mechanism for biodegradation of chlorinated aromatics, along with the cleavage of aromatic rings. The removal of the chlorine substituents has been known as a key step for degradation of chlorinated aromatic compounds under aerobic condition. This can occur as an initial step via oxygenolytic, reductive, and hydrolytic mechanisms. The studies on the biochemistry and genetics about microbial dechlorination give us the potential informations for microbial degradation of xenobiotics contaminated in natural microcosms. Such investigations might provide biotechnological approaches to solve the environmental contamination, such as designing effective bioremediation systems using genetically engineered microorganisms.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.5
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• pp.304-311
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• 2012

Chlorinated ethylenes such as perchloroethylene (PCE) and trichloroethylene (TCE) are widely used as industrial solvents and degreasing agents. Because of improper handling, these highly toxic chlorinated ethylenes have been often detected from contaminated soils and groundwater. Biological PCE dechlorination activities were tested in bacterial cultures inoculated with 10 different environmental samples from sediments, sludges, soils, and groundwater. Of these, the sediment using culture (SE 2) was selected and used for establishing an efficient PCE dechlorinating enrichment culture since it showed the highest activity of dechlorination. The cathode chamber of bioelectrochemical system (BES) was inoculated with the enrichment culture and the system with a cathode polarized at -500 mV (Vs Ag/AgCl) was operated under fed-batch mode. PCE was dechlorinated to ethylene via TCE, cis-dichloroethylene, and vinyl chloride. Microbial community analysis with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) showed that the microbial community in the enrichment culture was significantly changed during the bio-electrochemical PCE dechlorination in the BES. The communities of suspended-growth bacteria and attached-growth bacteria on the cathode surface are also quite different from each other, indicating that there were some differences in their mechanisms receiving electrons from electrode for PCE dechlorination. Further detailed research to investigate electron transfer mechanism would make the bioelctrochemical dechlorination technique greatly useful for bioremediation of soil and groundwater contaminated with chlorinated ethylenes.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.185-185
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• 2007

Starting at the beginning q the 20th century, increasing amounts of tetrach1oroethene (PCE) and trichloroethene (TCE)were manufactured due to the extensive use of these compounds in industry, in the military, and in private households, mainly as nonflammable solvents. This widespread use, along with careless handling and storage, are among the most serious contaminants of soil, sediment and groundwater. Highly chlorinated ethenes are typically not degraded through oxygenation by aerobic bacteria Since complete reductive dechlorination of PCE and TCE to ethene (ETH) has been observed in anaerobic enrichment culture, anaerobic dehalorespiring bacteria have received increased attention in the last decade. Under anaerobic conditions, these compounds con be reductively dehalogenated to less-chlorinated ethenes or innocuous ethene by microorganism through dehalorespiration. We have been studying anaerobic enrichment culture which used lactate as the electron donor for reductive dechlorination of PCE to ETH the anaerobic mixed microbial culture was enriched from the sediment sample taken from site contaminated with PCE. PCE was consistently and completely converted to ethene. In addition, the accumulation of intermediate products such as 1,2-ds-dichloroethene (cis-DCE) and vinyl chloride (VC) was observed in the anaerobic mixed microbial culture. the established dechlorinating enrichment culture was analyzed by DGGE using primers specific to DefrJ1ococcoides 16S rRNA gene sequences. In conclusion, we established the PCE dechlorinating enrichment culture and confirmed the existence of Dehalococcoides in an enrichment culture.

• The Journal of Engineering Geology
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• v.13 no.4
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• pp.389-404
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• 2003

VOCs were detected in the 21 groundwaters out of 37 groundwaters sampled from around the Hanam Industrial Complex and the Gwangju stream. Ten components of chlorinated aliphatic hydrocarbons of VOCs were detected in the 18 groundwater samples. Among them, total trihalomethanes (TTHM) concentration is in the range of $0.1~36.2{\;}\mu\textrm{g}/L$, CECs concentration is $2.3~190{\;}\mu\textrm{g}/L$, and chlorinated solvents concentration containing PCE, TCE, etc. is $0.1~124.2{\;}\mu\textrm{g}/L$ respectively. Ten components of the aromatic hydrocarbons of VOCs were detected in the 5 groundwater samples, but their concentration are less than $1{\;}\mu\textrm{g}/L$. Detection frequency and concentration of the chlorinated aliphatic hydrocarbons components from the groundwaters in the Hanam Industrial Complex are higher than those of nearby downtown Gwangju stream. VOCs components except for TCE are lower than the MCL of USGS drinking water standard. TCE concentration of the 2 groundwater samples is over MCL, whose concentrations are 5 and 25 times higher than MCL, respectively. TCE is detected from the H8 and H10 groundwater samples and CFCs is detected H8 and H11 groundwater samples in the Hanam Industrial Complex. TTHM in study area is estimated from leakage of the main waters or sewage waters. Because most of the studied groundwater is under an aerobic condition, aromatic hydrocarbons are well degraded. But chlorinated aliphatic hydrocarbons are degraded very slowly.

• Journal of the Korean Chemical Society
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• v.20 no.3
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• pp.229-235
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• 1976

Phenylacetic acid is chlorinated photochemically in carbon disulfide and carbon tetrachloride solvents to obtain ${\alpha}$-chlorophenylacetic acid in $43{\%}$ yield (after separation and purification). The amination of ${\alpha}$-chlorophenylacetic acid yielded the desired dl-phenylglycine in $16\sim27{\%}$ yield depending on the solvent used. Sensitized photophenylation of glycine is also attempted utilizing benzoylperoxide as a phenyl radical source in benzene or acetone solvent.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.62-65
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• 2002

Permeable reactive barriers (PRBs) are in-situ barriers constructed in a subsurface to treat contaminated groundwater using various reactive media. The common reactive medium used in PRB is zero-valent iron, which has been widely used to treat chlorinated solvents (i.e., PCE, TCE). A disadvantage of iron media is high cost. In this study, waste foundry sands were tested to determine the feasibility of their use as a low cost reactive medium. Batch and column tests were conducted with TCE to determine transport parameters and reactivity of the foundry sands. The reactivities of foundry sands for common groundwater contaminants are comparable to or slightly higher than those for Peerless iron, a common medium used in PRBs. In addition, the TOC and clay in foundry sands can significantly retard the movement of target contaminant, which may result in lower effluent concentration of contaminant due to biodegradation. In general, PRBs 1-m thick can be constructed with many foundry sands to treat TCE provided the zero-valent iron content in the foundry sand is higher than 1%.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.218-222
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• 2004

Batch slurry experiments were conducted to develop cement/slag/Fe(II) system that could treat hazardous liquid wastes containing halogenated organic solvents. Portland cement in combination with Fe(II) was reported to reductively dechlorinate chlorinated organics in a modified solidification/stabilization process. TCE (trichloroethylene) was used a model halogenated organic solvent. The objectives of this study were to assess the feasibility of using cement and steel converter slag amended with Fe(II) as a low cost abiotic reductive dechlorination and to investigate the kinetics of TCE dechlorination over a wide range of TCE concentration. From the result of screening experiments, cement/slag/Fe(II) system was identified as a potentially effective system to treat halogenated organic solvent. Kinetic studies were carried out to further investigate degradation reaction of TCE NAPL (Non Aqueous Phase Liquids) in cement/slag/Fe(II) systems by using batch slurry reactors. Degradation rate of TCE solution in this system can be explained by pseudo-first-order rate law because the prediction with the rate law is in good agreement with the observed data.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.117-121
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• 2002

A numerical model that describes the reductive dechlorination of tetrachloroethene(PCE) to ethene via cis-dichloroethene(CDCE) was developed. The model included two separated dehalogenator groups : one for PCE transformation to cDCE via TCE and the other for cDCE dehalogenation to ethene via VC, competitive inhibition between different chloroethene electron accepters, and competition for H$_2$ between dechlorination and methanogens. Model simulations suggest first, that PCE dechlorinators are better competitive with methanogens than cDCE dechlorinators. Second, not only the initial relative population size of dehalogenators and H$_2$-utilizing methanogens but also electron donor delivery strategies used greatly affects the degree of dehalogenation. As a result, all of factors in the above must be considered in order to achieve economical and successful bioremediation of contaminated soil and groundwater with chlorinated solvents.

• Journal of the Korean Chemical Society
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• v.41 no.10
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• pp.535-540
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• 1997

Potassium carbonate reacts with silicon tetrachloride to form trichlorosilyloxy carbonylchloride which reacts subsequently with another molecule of silicon tetrachloride leading to phosgene eventually in chlorinated solvents. This in situ generated trichlorosilyloxy carbonylchloride or phosgene were found to be very effective for the chlorination of a wide variety of alcohols to the corresponding chlorides. Primary, secondary and benzylic alcohols were converted into corresponding chlorides when treated with silicon tetrachloride in the presence of potassium carbonate at room temperature.