• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.822-828
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• 2005

The photocatalytic degradation of methyl parathion was carried out using a circulating $TiO_2$/solar system. Under the photocatalytic condition, parathion was more effectively degraded than by the photolysis or $TiO_2$ only condition. The parathion degradation followed pseudo first-order kinetics. With photocatalysis, 10 mg/L parathion was completely degraded within 90 min with a TOC decrease exceeding 63% after 150 min. The nitrogen from parathion was recovered mainly as ${NO_2}^-$, ${NO_3}^-$, and ${NH_4}^+$, 80% of sulfur as ${SO_4}^{2-}$, and less than 5% of phosphorus as ${PO_4}^{3-}$ during photocatalysis. The organic intermediates 4-nitrophenol and paraoxon were also identified, and these were further degraded. Two different bioassays using V. fischeri and D. magna were employed to measure the toxicity reduction in the solutions treated by both photocatalysis and photolysis. Relative toxicity was reduced almost completely after 150 min in both organisms under the photocatalysis, whereas in photolysis, 76 and 57% reduction was achieved for V. fischeri and D. magna, respectively. The acute toxicity reduction pattern corresponded with the decrease in parathion and TOC concentrations.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.1-10
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• 2005

The purpose of this study was to evaluate the potential of a gamma irradiation to decompose 2,4,6-trinitrotoluene(TNT) in an aqueous solution. The decomposition reaction of TNT by gamma irradiation was a pseudo first-order kinetic over the applied initial concentrations($25{\sim}100mg/L$). The dose constant was strongly dependent on the initial TNT concentration. The removal of TNT was more efficient at pH below 3 and at pH above 11 than at neutral pH(pH 5-9). The required irradiation dose to remove over 99% of TNT was 40, 80 and 10 kGy, individually at pH 2, 7 and 13. The dose constant was increased by 1.6 fold and over 15.6 fold at pH 2 and 13, respectively, when compared with that at pH 7 When irradiation dose of 200 kGy was applied, the removal efficiencies of TOC were 91, 46 and 53% at pH 2, 7 and 13, respectively. Ammonia and nitrate were detected as the main nitrogen byproducts of TNT and glyoxalic acid and oxalic acid were detected as organic byproducts. The results showed that a gamma irradiation was an attractive method for the decomposition of TNT in an aqueous solution. However, regarding the application of high energy radiation for the TNT decomposition and mineralization, an application of an acidic pH below 3 to the solution before irradiation should be considered.

• Journal of Soil and Groundwater Environment
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• v.13 no.5
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• pp.8-19
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• 2008

The physicochemical properties of soils having high uranium content, located around Duckpyungri in Korea, were investigated and the lab scale soil washing experiments to remove uranium from the soil were preformed with several washing solutions and on various washing conditions. SPLP (Synthetic Precipitation Leaching Procedure), TCLP (Toxicity Characteristic Leaching Procedure), and SEP (Sequential Extraction Procedure) for the soil were conducted and the uranium concentration of the extracted solution in SPLP was higher than Drinking Water Limit of USEPA (30 ${\mu}g$/L), suggesting that the continuous dissolution of uranium from soil by the weak acid rain may generate the environmental pollution around the research area. For the soil washing experiments, the uranium removal efficiency of pH 1 solution for S2 soil was about 80 %, but dramatically decreased as pH of solution was > 2, suggesting that strong acidic solutions are available to remove uranium from the soil. For solutions with 0.1M of HCl and 0.05 M of ${H_2}{SO_4}$, their removal efficiencies at 1 : 1 of soil vs. washing solution ratio were higher than 70%, but the removal efficiencies of acetic acid, and EDTA were below 30%. At 1 : 3 of soil vs. solution, the uranium removal efficiencies of 0.1M HCl, 0.05 M ${H_2}{SO_4}$, and 0.5M citric acid solution increased to 88%, 100%, and 61% respectively. On appropriate washing conditions for S2 soil such as 1 : 3 ratio for the soil vs. solution ratio, 30 minute for washing time, and 2 times continuous washing, TOC (Total Organic Contents) and CEC (Cation Exchange Capacity) for S2 soil were measured before/after soil washing and their XRD (X-Ray Diffraction) and XRF (X-Ray Fluorescence) results were also compared to investigate the change of soil properties after soil washing. TOC and CEC decreased by 55% and 66%, compared to those initial values of S2 soil, suggesting that the soil reclaimant may need to improve the washed soils for the cultivated plants. Results of XRF and XRD showed that the structural change of soil after soil washing was insignificant and the washed soil will be partially used for the further purpose.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1337-1344
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• 2007

In this research, we synthesized potassium ferrate(VI) acting as an oxidant, disinfectant, and coagulant, and used it to treat natural organic matter(NOM, HA and FA) in river water. The removal efficiencies obtained by $UV_{254}$ ranged from 20.7 to 73.6% for 10 mg/L HA and from 52.6 to 77.5% for 10 mg/L FA in Nakdong river sample as the ferrate dose varied from 2 to 46 mg/L(as Fe). However, the removal efficiencies by TOC analysis ranged from 0 to 20.3% for HA and from 0 to 26.6% for FA at the same ferrate doses. The removal efficiencies of NOM increased either with decreasing pH or with increasing temperature. The removal efficiency of HA by ferrate was comparable to those by traditional coagulants such as $Al_2(SO_4)_3{\cdot}18H_2O$, $FeSO_4{\cdot}7H_2O$, and FeO(OH). The reaction between ferrate and HA reached a steady state within 60 seconds, showing first-order with respect to the reaction time. The removal efficiencies of HA by traditional coagulants were improved by pretreatment of HA using a small amount of ferrate.

• Proceedings of KOSOMES biannual meeting
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• 2007.05a
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• pp.91-96
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• 2007

Lab scale experimental study was carried out for SBR process, to investigate the effects of influent ship sewage organic compound removal and Bacillus sp. state on design parameters. This process was able to remove nitrogen and phosphorus as well as organic matter efficiently. More than 95% of chemical oxygen demand(COD) were removed. In addition, about 97% of total nitrogen (T-N) was reduced. The total phosphorus(T-P) reduction averaged 93%. The performance load of SBR process was shown to be $0.095kg{\cdot}TOC/m^3{\cdot}day$. The pH was decreased from 8.1 to 7.0 within 30 min and increased to 7.3 at the end of anoxic stage, and these phenomena were explained. The sludge produced in the SBR process is characterized by low generation rate (about $0.36kg{\cdot}MLSS/kg{\cdot}TOC$) and excellent settleability. The number of Bacillus sp. in the SBR was 24.2%, indicating that Bacillus sp. was a predominant species in the reactor.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.241-249
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• 2000

In this study, UV-catalyzed $H_2O_2$ oxidation and $H_2O_2$ oxidation to remove contaminants from photo processing chemicals were investigated at various conditions. Photo processing chemicals contains high concentrations of organic compounds and has very low biodegradability. Hydrogen peroxide is subjected to gradual decomposition as metastable substance. In the process, short-lived and highly reactive hydroxyl radicals are formed. The decomposition can be significantly accelerated by use of appropriate catalyst, such as ultraviolet radiation. The experiments were conducted in a UV-free reflecting reactor in batch and a high-pressure mercury lamp was used as UV source. Mixing, cooling and ventilation of the reactor were operated during experiments. In $UV/H_2O_2$ oxidation and $H_2O_2$ oxidation, the removal efficiencies of $COD_{Cr}$, TOC and chromaticity increased with the increase of $H_2O_2$ dosage and were higher in the controlled pH condition of 3 than in original pH condition of 8. In $UV/H_2O_2$ oxidation under the optimum condition of pH 8 and 1.3 stoichiometric $H_2O_2$ dosage, the removal efficiencies of $COD_{Cr}$, TOC and chromaticity were 47.5%, 75.0% and 91.5% respectively and $BOD/COD_{Cr}$ ratio was significantly increased from 0.04 to 0.21.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.570-575
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• 2018

The various of raw wastewater inflows to the industrial wastewater treatment plants everyday. This makes it difficult to operate the coagulation and flocculation efficiently as a pretreatment process for the industrial wastewater treatment. Additionally, it causes loads on evaporation and membrane facilities which are the posttreatment and alternative processes. For this reason, this study sampled raw wastewater before and after the NaOH injection. An experiment was conducted to compare the coagulation characteristics according to the methods of coagulant injection (single injection, simultaneous injection, consecutive injection, and inverse injection) aiming at efficient treatment of industrial wastewater. The coagulation experiment was conducted using a jar tester. The TDS removal efficiency by the coagulant injection methods increased in the order of consecutive injection (2.8 %) < single injection (3.9 %) < simultaneous injection(8.1 %) < inverse injection(9.6 %); the TOC removal efficiency grew in the order of single injection (84.3 %) < inverse injection (86.2 %) < consecutive injection (88.6 %) < simultaneous injection (89.1 %); the turbidity removal efficiency grew from single injection (99.7 %) < consecutive injection (99.8 %) ${\fallingdotseq}$ inverse injection (99.8 %) < simultaneous injection (99.9 %). These results show that the simultaneous inorganic coagulant-polymer coagulant injection method was more efficient than the consecutive injection method (inorganic coagulant ${\rightarrow}$ polymer coagulant).

• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.137-143
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• 2006

Three candidate processes(ozone alone, UV alone and ozone/UV combined processes) were evaluated for the removal of diethyl phthalate(DEP). Of the candidates, the ozone/UV process showed the highest removal efficiency of DEP. To elucidate a major oxidant for DEP oxidation in the ozone/UV process, the effects of pH and hydroxyl radical($OH^{\circ}$) scavenger were investigated. As a result, it was found that $OH^{\circ}$ plays a important role for DEP elimination. Meanwhile, the direct reaction between ozone and DEP was negligible. Observing the pseudo first-order rate of DEP removal in ozone alone and ozone/UV processes, the different pattern was obtained from two processes. The ozone/UV process was well plotted following the pseudo first-order. but in the ozone alone process the rate was divided into fast and slow phases. DEP degradation characteristics in ozone alone and ozone/UV was also investigated by observing the HPLC spectrum. We detected unknown compounds that were guessed to DEP byproducts and observed the formation and disappearance of the unknown compounds according to reaction time. Observing of high removal of TOC in ozone/UV combined process, it was found that DEP and DEP byproducts are completely oxidized by ozone/UV combined process.

• Journal of Life Science
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• v.9 no.6
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• pp.698-703
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• 1999

For the nitrate removal in recirculating aquaculture system, a denitrifying bacterium, Pseudomonas fluorescens, was isolated from municipal sewage and the cells were immobilized in modified-polyvinly alchol (PVA) gel beads. The immobilized cells in both the fixed-and fluidized-bed reactors showed 98% of denitrification efficiency with 6hr HRT, and the removal efficiency of total organic carbon (TOC) was above 90%. Form scanning electron microscopy (SEM) observation, it was known that biofilm formed in fixed-bed reactor was thicker than that formed in fluidized-bed reactor as operation time passed.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2001.05a
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• pp.138-139
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• 2001

$TiO_2$/UV 고급 산화 공정을 실제 산업 폐수에 적용하였다. 회분식 원통형 반응기에서 T산업 폐수를 광반응시킨 결과 COD 값과 TOC 값이 24시간 경과된 후 95% 이상의 제거 효율을 나타내었다. 광반응에 미치는 인자에 대한 연구에서 $TiO_2$ powder가 0.1 $g/{\ell}$ 에서 8 $g/{\ell}$까지는 투입된 광촉매의 량과 광반응속도가 비례적으로 증가되었으나 10 $g/{\ell}$ 이상에서는 광차폐효과가 나타나 광반응속도가 감소하였으며, UV 광원이 강할수록 광반응 속도는 증가하였고 초기 pH는 광촉매 반응에 영향을 미치지 않음을 알 수 있었다.