• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.764-769
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• 2006

In the electrokinetic(EK) process, oxygen production by electrolysis was proportional to current density. The dissolved oxygen (DO) concentration in anode tank and bioreactor increased with the circulation rate of electrolyte. The bacterial population in bioreactor rapidly increased by the supplement of current, but the DO concentration deceased by the increased bacterial oxygen consumption. From the results of EK bioremediation for pentadecane-contaminated soil, the bacterial population and removal efficiency at 1.88 $mA/cm^2$ were lower than those at 0.63 $mA/cm^2$. This is because the high oxygen production rate largely increased the production rate of organic acids, which reduced the electrolyte pH and bacterial activity. At 0.63 $mA/cm^2$, the highest bacterial population and removal efficiency could be obtained due to the appropriate oxygen production and small decrease in pH.

• KSBB Journal
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• v.21 no.3
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• pp.175-180
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• 2006

In this study, it could be found that the microbial movement in soil under electric field mainly occurred by electrophoresis and electroosmosis. The contribution of electrophoresis on the microbial mobility and flux was generally higher than that of electroosmosis. In the electrokinetic(EK) bioremediation of a pentadecane-contaminated soil, the microbial population increased simultaneously at anode and cathode regions of the soil specimen because both electrophoresis and electroosmosis affected on the microbial movement. After initial operation, the microbial population was high in order of anode, middle, and cathode regions due to their negatively-charged surface and oxygen generation at anode. However, the uniform contaminant removal was achieved by the microbial movement with two-directionality.

• KSBB Journal
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• v.21 no.3
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• pp.181-187
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• 2006

In this study, problems related with pH control in electrokinetic(EK) bioremediation of phenanthrene contaminated soil were observed, and the effects of pH control methods on the removal efficiency were investigated to search a further application strategy. In a preliminary experiment, it was found out by flask cultivation that a certain sulfate concentration was needed to degrade phenanthrene well using Sphingomonas sp. 3Y. However, when $MgSO_4$ was used as sulfate source in EK bioremediation, the bacterial activity reduced seriously due to the abrupt decrease of pHs in soil and bioreactor by the combination of magnesium and hydroxyl ions. When another strong buffering compound was used to control the pH problem, the good maintenance of the bacterial activity and pHs could be observed, but the removal efficiency decreased largely. When a low concentration of $MgSO_4$ was added, the removal efficiency decreased somewhat in spite of the good maintenance of neutral pHs. With the addition of NaOH as a neutralizing agent, the removal efficiency also decreased because of the increase of soil pH. Consequently the selection of electrolyte composition was a very important factor in EK bioremediation and some sulfate sources suitable for both bacterial activity and contaminant degradation should be investigated.

• KSBB Journal
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• v.21 no.6 s.101
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• pp.428-432
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• 2006

This study investigated the effect of sulfate source on removal efficiency in electrokinetic bioremediation which needs sulfate to degrade contaminants by an applied microorganism. The representative contaminant and the applied microorganism were phenanthrene and Sphingomonas sp. 3Y, respectively. When magnesium sulfate was used, the magnesium ion combined with hydroxyl ion electrically-generated at cathode to cause the decrease of electrolyte pH, and then the microbial activity was inhibited by that. When ammonium sulfate and disodium sulfate were used to solve the pH control problem, the pH values of electrolyte and soil solution were maintained neutrally, and also the high microbial activity was observed. With the former sulfate source, however, ammonium retarded the phenanthrene degradation, and so the removal efficiency decreased to 12.0% rather than 21.8% with magnesium sulfate. On the other hand, the latter improved the removal efficiency to 27.2%. This difference of removal efficiency would be outstanding for an elongated treatment period.

• Journal of Soil and Groundwater Environment
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• v.7 no.1
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• pp.15-24
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• 2002

Nowdays electrokinetic technique has been applied to supply nutrients and TEAs for in-situ bioremediation. However the Injection characteristics under electrical field have not been examined in various soil types. Therefore, The characteristics of electrokinetic injection into kaolinite and sand are investigated. During the 17 d of processing, There was a gradual increase in ammonium (nutrient) concentration from the anode compartment. However the ammonium concentration at the cathode increased beyond that at the anode in sand. A relatively constant profile of sulfate (TEA) was achieved specifically, the final sulfate concentration in each specimen were different. When EK injection technique is implemented in field, the most important consideration should be an assessment of the injection characteristics with respect to the soil types.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.3
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• pp.245-251
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• 2016

Soil can be contaminated by radioactive materials due to nuclide leakage following unexpected situations during the decommissioning of a nuclear power plant. Soil decontamination is necessary if contaminated land is to be reused for housing or industry. The present study classifies various soil remediation technologies into biological, physics/chemical and thermal treatment and analyzes their principles and treatment materials. Among these methods, this study selects technologies and categorizes the economics, applicability and technical characteristics of each technology into three levels of high, medium and low by weighting the various factors. Based on this analysis, the most applicable soil decontamination technology was identified.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.186-190
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• 2004

The electrokinetic bioremediation employing electrolyte circulation method was carried out for the cleanup of phenanthrene-contaminated kaolinite, and microorganism used in the biodegradation of phenanthrene was Sphingomonas sp. 3Y. The electrolyte circulation method supplied ionic nutrientsand the microorganism into soil, and inhibited the significant pH change of soil by increasing the soil buffering capacity by providing phosphate buffer compounds. When the remediation process was conducted without surfactant, the removal efficiency of phenanthrene, at the initial concentration of 200 ppm, was 69% for only 7 days. Higher microbial population and lower phenanthrene concentration were observed in the anode and middle regions of soil specimen than in the cathode region. The higher density of microorganism was because the microbial movement was in the direction of the anode part due to the negative surface charge. When Triton X-100 and APG of 20 g/1 were used to improve the bioavailability of phenanthrene strongly adsorbed onto soil surface, about 90 and 39% of phenanthrene removal were obtained. Consequently, it was confirmed that the microorganism preferred APC to phenanthrene as carbon source and so the removal efficiency with APG decreased less than that without APG.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.181-185
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• 2004

Electrokinetic bioremediation was conducted on phenanthrene-contaminated soil to study the effects of soil temperature and pH on microbial population and removal efficiency at different current densities from 0.63 to 3.13 mA cm$^{-2}$ . Microorganism used in the biodegradation of phenanthrene was Sphingomonas sp. 3Y, which was isolated from a diesel-contaminated site. The microorganism was successfully penetrated into the contaminated soil by electrokinetic phenomena and the highest microbial population was observed in the middle region of soil specimen where soil pH was near neutral. Therefore, phenanthrene removal occurred mainly at anode and middle parts of soil specimen due to a relatively high microbial population. Also, the highest removal efficiency of 68.8% was obtained at 1.88 mA cm$^{-2}$ while low degradation was detected at 3.13 mA cm$^{-2}$ . It was presumably because the soil temperature at 1.88 mAcm$^{-2}$ was close to the appropriate temperature of about 30'c while the temperature increase to above 45$^{\circ}C$ at 3.13 mA cm$^{-2}$ inhibited the microbial activity severely.