• Journal of Soil and Groundwater Environment
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• v.23 no.4
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• pp.42-47
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• 2018

E. coli TG1 pBS TOM Green was cultured to produce toluene-o-monooxygenase (TOM). A biosensor system was successfully constructed using purified TOM to effectively detect trichloroethene (TCE) and tetrachloroethene (PCE), which represent some of the major contaminants in groundwater and soil. In order to utilize TOM as a sensor, NADH, a biological oxidizer, was replaced with hydrogen peroxide which is a chemical oxidizing agent. A three-layered sandwich-type sensing tip was fabricated on the outside of the hydrophilic polyvinylidene fluoride membrane. TCE and PCE were applied to the sensor and the hydrogen ions were measured by a fiber optic fluorometer using fluoresceinamine. Calibration curves were obtained for TCE and PCE in the concentration range of 0.2-100 mg/l, and the detection limit of the system was $10{\mu}g/l$ for TCE and PCE.

• Environmental Engineering Research
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• v.10 no.2
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• pp.79-87
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• 2005

The effects of transformation capacity on cometabolic degradation of trichloroethene (TCE) were evaluated using TCE-degrading actinomycetes pure and mixed culture under various culture conditions. The TCE transformation capacity of the actinomycetes enrichment culture in a batch test with phenol addition was 1.0 mg of TCE/mg of volatile suspended solids (VSS). The resting cell TCE transformation capacity of the actinomycetes pure culture cell was 0.75 mg TCE/mg VSS, which increased to 2.0 mg TCE/mg VSS when phenol was added as an external substrate. When the pure culture had an internal substrate in the form of poly-β-hydroxybutyrate (PHB) at 19% of the cell mass, the resting cell TCE transformation capacity increased from 0.47 to 0.6 mg TCE/mg VSS. The presence of PHB increased transformation capacity by 57%, whereas, the addition of phenol caused more than two fold increase in transformation capacity. The actinomycetes culture showed the highest transformation capacity.

• Economic and Environmental Geology
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• v.34 no.3
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• pp.307-313
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• 2001

Reactive medium including zero-valent metals such as zero-valent iron ($Fe^0$) degrades chlorinated solvents as a contaminant plume flows through the treatment medium. Although the Feo based reactive barrier has been demonstnlted to be a cost effective for trichloroethenc (TCE)-contaminaled plume remediation, current approach is limited by low process eftlciency and uncertain, effective life of the medium. The objective of this study is to develop an enhanced treatment method of TeE-contaminated groundwater using Feo and direct current. The bench-scale test using flow-through $Fe^0$ reactor column confirmed that the application of direct current with $Fe^0$ is highly effective in enhancing the rate of TeE dechlorination. The dechlorination mechanism appears to be reductive, with the electrons supplied by the iron oxidation and external power supply serving as the additional source of electrons.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.53-56
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• 2001

The degradation of tetrachloroethene (PCE) and trichloroethene (TCE) by vitamin B$_{12}$, an electron mediator was examined when zero valent metals (ZVMs) were used as built electron donors. Dechlorination of PCE and TCE by iron and zinc in the presence of vitamin B$_{12}$ showed that the zinc and vitamin B$_{12}$ combination greatly enhances the reaction rates for both PCE and TCE, but iron and vitamin B$_{12}$ result in an increase in reactivity only for PCE degradation, not for TCE degradation in comparing with meta]s only. This result indicates vitamin B$_{12}$(I) Is active towards both PCE and TCE degradation while vitamin B$_{12}$(II) is active towards both PCE. Calculated activation energies for the dechlorination of PCE in the presence of Vitamin B$_{12}$ showed that vitamin B$_{12}$ lowered the activation energy about 40-60 kJ/㏖ for the both metals.the both metals.

• Journal of the Korean Applied Science and Technology
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• v.24 no.4
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• pp.436-443
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• 2007

Anaerobic reductive dehalogenation of perchloroethene (PCE) was studied with lactate as the electron donor in a continuously stirred tank reactor (CSTR) inoculated with a mixed culture previously shown to dehalogenate vinyl chloride (VC). cis-1,2- dichloroethene (cDCE) was the dominant intermediate at relatively long cell retention times (>56 days) and the electron acceptor to electron donor molar ratio (PCE:lactate) of 1:2. cDCE was transformed to VC completely at the PCE to lactate molar ratio of 1:4, and the final products of PCE dehalogenation were VC (80%) and ethene (20%). VC dehalogenation was inhibited by cDCE dehalogenation. Propionate produced from the fermentation of lactate might be used as electron donor for the dehalogenation. Batch experiments were performed to evaluate the effects of increased hydrogen, VC, and trichloroethene (TCE) on VC dehalogenation which is the rate-limiting step in PCE dehalogenation The addition of TCE increased the VC dehalogenaiton rate more than an increase in the $H_2$ concentration, which suggests that the introduction of TCE induces the production of an enzyme that can comtabolize VC.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.127-130
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• 2005

The feasibility of stimulating in situ aerobic cometabolic activity of indigenous microorganisms was investigated in a trichloroethene(TCE)-contaminated aquifer, A series of single-well natural drift tests (SWNDT) was conducted by injecting site groundwater amended with a bromide tracer and combinations of toluene, oxygen, nitrate, ethylene and TCE into an existing monitoring well and by sampling the same well over time. Transformation of ethylene, a surrogate of overall TCE transformation activity, was also observed, and its transformation results in the production of ethylene oxide, suggesting that some tolune-oxidizing microorganisms stimulated may express a monooxygenase enzymes. Also in situ transformation of TCE was confirmed by dilution-adjusted data analysis developed in this study. These results indicate that, in this environment, toluene and oxygen additions stimulated the growth and aerobic cometabolic activity of indigenous microorganisms expressing monooxygenase enzymes and that these are responsible for observed toluene utilization and cometabolism of ethylene and TCE. The simple, low-cost field test method provides an effective method for conducting rapid field assessments and pilot testing of aerobic cometabolism of TCE, which has previously hindered application of this technology to groundwater remediation.

• Journal of Microbiology and Biotechnology
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• v.26 no.1
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• pp.120-129
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• 2016

An industrial complex in Wonju, contaminated with trichloroethene (TCE), was one of the most problematic sites in Korea. Despite repeated remedial trials for decades, chlorinated ethenes remained as sources of down-gradient groundwater contamination. Recent efforts were being made to remove the contaminants of the area, but knowledge of the indigenous microbial communities and their dechlorination abilities were unknown. Thus, the objectives of the present study were (i) to evaluate the dechlorination abilities of indigenous microbes at the contaminated site, (ii) to characterize which microbes and reductive dehalogenase genes were responsible for the dechlorination reactions, and (iii) to develop a PCE-to-ethene dechlorinating microbial consortium. An enrichment culture that dechlorinates PCE to ethene was obtained from Wonju stream, nearby a trichloroethene (TCE)-contaminated industrial complex. The community profiling revealed that known organohalide-respiring microbes, such as Geobacter, Desulfuromonas, and Dehalococcoides grew during the incubation with chlorinated ethenes. Although Chloroflexi populations (i.e., Longilinea and Bellilinea) were the most enriched in the sediment microcosms, those were not found in the transfer cultures. Based upon the results from pyrosequencing of 16S rRNA gene amplicons and qPCR using TaqMan chemistry, close relatives of Dehalococcoides mccartyi strains FL2 and GT seemed to be dominant and responsible for the complete detoxification of chlorinated ethenes in the transfer cultures. This study also demonstrated that the contaminated site harbors indigenous microbes that can convert PCE to ethene, and the developed consortium can be an important resource for future bioremediation efforts.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.685-693
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• 2008

The rates of oxidative degradation of perchloroethene (PCE) and trichloroethene (TCE) using $KMnO_4$ solution were evaluated under the flow condition using a bench-scale transport experimental setup. Parameters which are considered to affect the reaction rates tested in this study were the contact time (or retention time), and the concentration of oxidizing agent. A glass column packed with coarse sand was used for simulating the aquifer condition. Contact time between reactants was controlled by changing the flow rate of the solution through the column. The inflow concentrations of PCE and TCE were controlled constant within the range of $0.11{\sim}0.21\;mM$ and $1.3{\sim}1.5\;mM$, respectively. And the contact time was $14{\sim}125$ min for PCE and $15{\sim}36$ min for TCE. The $KMnO_4$ concentration was controlled constant during experiment in the range of $0.6{\sim}2.5\;mM$. It was found that the reduction of PCE and TCE concentrations were inversely proportional to the contact time. The exact reaction order for the PCE and TCE degradation reaction could not be determined under the experimental condition used in this study. However, the estimated reaction rate constants assuming pseudo-1st order reaction agree with those reported based on batch studies. TCE degradation rate was proportional to $KMnO_4$ concentration. This was considered to be the result of using high inflow concentrations of reactant, which might be the case at the vicinity of the source zones in aquifer. The results of this study, performed using a dynamic flow system, are expected to provide useful information for designing and implementing a field scale oxidative removal process for PCE/TCE-contaminated sites.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.42-45
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• 2005

Accurate prediction of the fate and transport of contaminants in soils and sediments is very Important to environmental risk assessment and effective remediation of contaminated soils and sediments. The fate and transport of contaminants in subsurface are affected by geosorbents, especially carbonaceous materials including black carbon. Various physical and chemical treatment methods have been developed to separate different kinds of carbonaceous materials from soils and sediments. However, the effects of these separation methods on the properties of remaining carbonaceous materials including sorption capacity and linearity are unclear. The objective of this study is to determine if the chemical and thermal treatment methods previously used to separate different carbonaceous material fractions affect the properties of carbonaceous materials including longer term sorption capacity of hydrophobic organic contaminants. The results indicate that treatments with hydrochloric acid (HCl)/hydrofluoric acid (HF), trifluoroacetic acid (TFA), sodium hydroxide (NaOH) may not affect the sorption capacity of black carbon reference materials such as char and soot, however, treatments with acid dichromate $(K_2Cr_2O_7/H_2SO_4)$ and heat $(375^{\circ}C)$ for 24 hours in sufficient of oxygen) decrease the sorption capacity of them. The results of longer term sorption isotherm indicate that 2 days might be enough for trichloroethene (TCE) to equilibrate apparently with treated black carbon reference materials. The results suggest that acid dichromate and heat treatments may not appropriate method to investigate sorption properties of black carbon in soils and sediments.

• Journal of Soil and Groundwater Environment
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• v.17 no.5
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• pp.49-55
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• 2012

A 1.28 L-batch reactor and continuous-flow stirred tank reactor (CFSTR) fed with formate and trichloroethene (TCE) were operated for 120 days and 56 days, respectively, to study the effect of formate as electron donor on anaerobic reductive dechlorination (ARD) of TCE to cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethylene (ETH). In batch reactor, injected 60 ${\mu}mol$ TCE was completely degraded in the presence of 20% hydrogen gas ($H_2$) in less than 8 days by anaerobic dechlorination mixed-culture (300 mg-soluble protein), Evanite Culture with ability to completely degrade tetrachloroethene (PCE) and -TCE to ETH under anaerobic conditions. Once the formate was used as electron donor instead of hydrogen gas in batch or chemostat system, the TCE-dechlorination rate decreased and acetate production rate increased. It indicates that the concentration of hydrogen produced in both systems is possibly more close to threshold for homoacetogenesis process. Soluble protein concentration of Evanite culture during the batch test increased from 300 mg to 688 mg for 120 days. Through the protein monitoring, we confirmed an increase of microbial population during the reactor operation. In CFSTR test, TCE was fed continuously at 9.9 ppm (75.38 ${\mu}mol/L$) and the influent formate feed concentration increased stepwise from 1.3 mmol/L to 14.3 mmol/L. Injected TCE was accumulated at 18 days of HRT, but TCE was completely degraded at 36 days of HRT without accumulation of the injected-TCE during the left of experiment period, getting $H_2$ from fermentative hydrogen production of injected formate. Although c-DCE was also accumulated for 23 days after beginning of CFSTR operation, it reached steady-state in the presence of excessive formate. We also evaluated microbial dynamic of the culture at different chemical state in the reactor by DGGE (denaturing gradient gel electrophoresis).