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        • KCI등재

          Na<sub>2</sub>S를 이용한 EDTA 토양세척수로부터의 중금속 분리

          오상화,신원식,Oh, Sanghwa,Shin, Won Sik 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.7

          Soil washing with ethylenediaminetetraacetic acid (EDTA) is highly effective in the remediation of soils contaminated with heavy metals. The EDTA recycling process is a requisite for reducing the operating cost. The applicability of Na<sub>2</sub>S addition on the precipitation of heavy metals from the spent soil washing solution and thereby recycling of EDTA was investigated. Addition of Na<sub>2</sub>S into the single metal-EDTA and the mixed metal-EDTA solutions ([Na<sub>2</sub>S]/[metal-EDTA] ratio = 30, reaction time = 30 min and pH = 7~9) was highly effective in the separation of Cu and Pb from metal-EDTA complexes, but not for Ni. The Zn removal efficiency varied with pH and slightly increased upto 40% as the reaction time increased from 0 to 240 min which was longer than those for Cu and Pb. Ca(OH)<sub>2</sub> was subsequently added to induce further precipitation of Zn and Ni and to reduce the Na<sub>2</sub>S dose. At the [Na<sub>2</sub>S]/[metal-EDTA] ratio of 10, the removal efficiencies of all heavy metals excluding Ni were above 98% with the dose of Ca(OH)<sub>2</sub> at 0.002, 0.006 and 0.008 g into 100 mL of Cu-, Pb- and Zn-EDTA solutions, respectively. However, Ca(OH)<sub>2</sub> addition was not effective for Ni-EDTA solution. A further research is needed to improve metal removal efficiency and subsequent EDTA recycling for the real application in field-contaminated soils.

        • KCI등재

          담체 충진여부에 따른 회분식 반응기내 혐기성 암모니아 산화 미생물의 질소제거 경향

          오상화 ( Sanghwa Oh ) 한국수처리학회 2016 한국수처리학회지 Vol.24 No.2

          Anaerobic ammonium oxidation (anammox) coupled to nitrite or nitrate reduction is very slow reaction with about 20days of doubling time. For cultivation of the very slow growing bacteria, a sequencing batch reactor (SBR) is considered the most credible reactor and the utilization of media for providing a high biomass concentration using a vast surface area. This study compared the N removal efficiencies of SBR with fluidized media to those without media. The optimum operating time in SBR with and without media, when the removal efficiency of TN did not increase anymore, appeared at 21 h and 24h, respectively. The TN removal efficiency was 61% and 35% in SBR with and without packed media at 24 h. It is because NO_{3}^{-} and NH₃ in SBR with media were more removed and NO_{3}^{-} was less produced than those without media by anammox and denitrification bacteria.

        • KCI등재

          퇴적물에 대한 ibuprofen의 수착 및 탈착저항성

          오상화 ( Sanghwa Oh ) 한국수처리학회(구 한국수처리기술연구회) 2018 한국수처리학회지 Vol.26 No.4

          The isotherm sorption and sequential desorption of ibuprofen were investigated using wetland sediment with several conditions such as pH 3, 3% of salinity, and 1 M Na-citrate as a dissolved organic matter (DOM), and salinity on sorption and desorption of ibuprofen in water/sediment system. Two sorption models such as linear and Freundlich models and two desorption resistance models such as bi-phasic desorption model and its modified model were used to fit the experimental data. The linear and Freundlich models fitted well to the sorption data (R<sup>2</sup>>0.99) and the bi-phasic desorption model (BPDM) and the modified bi-phasic desorption model (MBPDM) also fitted well to the desorption data (R2>0.98). For sorption, KF in Freundlich model was estimated in order of 9.1 (3% salinity) > 7.4 (pH 3) > 4.8 (Na-citrate) in accordance to Kp in linear model. For desorption, both BPDM and MBPDM fitted well the sequential desorption experiments. The final desorption resistance were also positively affected by salinity but negatively influenced by the presence of Na-citrate as DOM.

        • KCI등재

          연속흐름식 반응조에서의 탈질소화와 혐기성 암모니아 산화 반응에 의한 질산성 질소 제거에 대한 유기물 주입 영향

          오상화 ( Sanghwa Oh ) 한국수처리학회 2016 한국수처리학회지 Vol.24 No.5

          In wastewater treatment plant, most of oxidized nitrogen is nitrate in aerobic and anoxic reactors. In this study, for this reason, we investigated the removal of nitrogen compounds via anaerobic ammonium oxidation (anammox) and denitrification by cell decay or external organics using a continuous flow reactor. The experiments consisted of three cases such as only media packed (case 1), only organic supplied (case 2) and both media packed and organic supplied (case 3). The mass balances for each case were conducted to analyze the nitrogen removal mechanism. FISH(fluorescence in situ hybridization) and image analysis technique was also used to calculate the content of anammox bacteria and nitrifying bacteria for each case. Conclusively, the organic supply made anammox reaction decreased and denitrification activated. Media supply was helpful to activate anammox. FISH analysis also presented that the content of anammox bacteria such as Brocadia Anammoxidans and Kuenenia Stuttgartiansis was increased when media was supplied.

        • KCI등재

          실리콘 튜빙 담지 폴리우레탄 생물벽체를 이용한 지하수내 질산성 질소 제거

          오상화 ( Sanghwa Oh ),신원식 ( Won Sik Shin ) 한국수처리학회(구 한국수처리기술연구회) 2018 한국수처리학회지 Vol.26 No.1

          A column reactor with biobarrier consisting of polyurethane-activated carbon (PU-AC) media with hollow silicon tubing coiled inside the media was operated to estimate the potential for treatment of nitrate-contaminated groundwater. The tubing was also evaluated for its potential to provide carbon sources such as glucose, methanol, ethanol, and acetic acid for denitrification process. Methanol was selected as the most effective carbon because the highest amount of methanol could be delivered with appropriate releasing rate. In a column experiment, the groundwater containing 60 mg/L of nitrate was flowed through the PU-AC biobarrier. Denitrification of NO<sub>3</sub> <sup>-</sup> coupled to carbon supply throughout the silicon tubing was successfully observed, depending on the groundwater velocity and methanol concentration. For satisfying potable groundwater criteria of nitrate (10 mg/L), 0.033 cm/min of groundwater velocity with 3% of methanol content in silicon tubing was appropriate corresponding to negative ORP value of -240 mV during denitrification. To deduce the optimum operating condition of the column reactor, the groundwater velocity was further reduced to 0.018 cm/min and the carbon content (%) was changed from 2.0 to 3.5% in the silicon tubing, which resulting in 3.5% of the optimum value (approximately 83% of NO<sub>3</sub>-N removal). At this point, the ORP showed all negative values, indicating that ORP can be used as an indicator of denitrification in biobarrier in field.

        • KCI등재

          국내 담수퇴적물의 COD<sub>sed</sub> 분석방법 평가: COD<sub>Mn</sub>법과 COD<sub>Cr</sub>법의 신뢰성 및 상관성 비교

          최지연,오상화,박정훈,황인성,오정은,허진,신현상,허인애,김영훈,신원식,Choi, Jiyeon,Oh, Sanghwa,Park, Jeong-Hun,Hwang, Inseong,Oh, Jeong-Eun,Hur, Jin,Shin, Hyun-Sang,Huh, In-Ae,Kim, Young-Hoon,Shin, Won Sik 한국환경과학회 2014 한국환경과학회지 Vol.23 No.2

          In Korea, the chemical oxygen demand($COD_{sed}$) in freshwater sediments has been measured by the potassium permanganate method used for marine sediment because of the absence of authorized analytical method. However, this method has not been fully verified for the freshwater sediment. Therefore, the use or modification of the potassium permanganate method or the development of the new $COD_{sed}$ analytical method may be necessary. In this study, two modified $COD_{sed}$ analytical methods such as the modified potassium permanganate method for $COD_{Mn}$ and the modified closed reflux method using potassium dichromate for $COD_{Cr}$ were compared. In the preliminary experiment to estimate the capability of the two oxidants for glucose oxidation, $COD_{Mn}$ and $COD_{Cr}$ were about 70% and 100% of theoretical oxygen demand(ThOD), respectively, indicating that $COD_{Cr}$ was very close to the ThOD. The effective titration ranges in $COD_{Mn}$ and $COD_{Cr}$ were 3.2 to 7.5 mL and 1.0 to 5.0 mL for glucose, 4.3 to 7.5 mL and 1.4 to 4.3 mL for lake sediment, and 2.5 to 5.8 mL and 3.6 to 4.5 mL for river sediment, respectively, within 10% errors. For estimating $COD_{sed}$ recovery(%) in glucose-spiked sediment after aging for 1 day, the mass balances of the $COD_{Mn}$ and $COD_{Cr}$ among glucose, sediments and glucose-spiked sediments were compared. The recoveries of $COD_{Mn}$ and $COD_{Cr}$ were 78% and 78% in glucose-spiked river sediments, 91% and 86% in glucose-spiked lake sediments, 97% and 104% in glucose-spiked sand, and 134% and 107% in glucose-spiked clay, respectively. In conclusion, both methods have high confidence levels in terms of analytical methodology but show significant different $COD_{sed}$ concentrations due to difference in the oxidation powers of the oxidants.

        • KCI등재

          토양내 오염된 2,4,6-trinitrotoluene (TNT)의 Eisenia fetida에 대한 독성 및 생물흡수

          최지연,오상화,신원식,Choi, Jiyeon,Oh, Sanghwa,Shin, Won Sik 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.6

          Toxicity and uptake of 2,4,6-trinitrotoluene (TNT) in three different soils (OECD soil, natural soil and loess) to earthworm (Eisenia fetida) were investigated at several different spiked concentrations of TNT (0 to 200 mg/kg for OECD and natural soils, and 0 to 35 mg/kg for loess) and for different exposure periods (7, 14, 21, and 28 d). The LC<SUB>50</SUB> values for 7 d exposure were 160.1, 159.4, and 28.81 mg/kg for OECD soil, natural soil, and loess, respectively. The LC<SUB>50</SUB> values for 14, 21, and 28 d exposure were almost the same as those for 7 d exposure, showing that 7 d exposure time was enough to decide the toxicity (LC<SUB>50</SUB>) of TNT to Eisenia fetida, because the highest concentration of TNT in earthworm body was observed within around 5 d. The LC<SUB>50</SUB> and uptake of TNT in loess were higher than those in OECD and natural soil. The uptake of TNT to the earthworm were correlated well with the initial concentration of TNT in the soil and TNT porewater concentration (R<SUP>2</SUP>> 0.9 in OECD, natural, and loess). The concentration of TNT in earthworm body decreased after 5 d, possibly caused by natural degradation of TNT by soil bacteria as well as earthworm.

        • KCI등재

          단일 고형화제를 이용한 중금속류 오염 토양의 고형화/안정화

          박혜옥,최지연,오상화,신원식,Park, Hye Ok,Choi, Jiyeon,Oh, Sanghwa,Shin, Won Sik 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.7

          Remediation of metal(loid)s-contaminated sites is crucial to protect human and ecosystem. Solidification and stabilization of metal(loid)s by the binder amendment is one of the cost-effective technologies. In this study, metal (loid)s in various field-contaminated soils obtained from steel-making, metal refinery and mining tillage were immobilized by the application of single binders such as diammonium phosphate (DAP), lime, and ladle slag. The efficiency of solidification and stabilization was evaluated by Toxicity Characteristic Leaching Procedure (TCLP) and the Standard, Measurements and Testing programme of European Union (SM&T) extraction processes. In terms of TCLP extraction, the binder was effective in order of lime > DAP > ladle slag. All binders were highly effective in the immobilization of Pb, Zn, Cu, Ni, and Cd. The increased immobilization efficiency is attributed to the increase in the Step III and IV fractions of the SM&T extraction. Lime and ladle slag were highly effective in the immobilization of the metal(loid)s, however, As release increased with DAP due to competition between the phosphate originated from DAP and arsenate. A further study is needed for the better immobilization of multi metal(loid)s using binary binders.

        • KCI등재

          Ca-Al-NO<sub>3</sub> 또는 Mg-Al-NO<sub>3</sub> 계열 층상이중수산화물을 이용한 염소이온 제거

          김광덕 ( Gwang-deuk Kim ),오상화 ( Sanghwa Oh ),김홍태 ( Hong-tae Kim ) 한국수처리학회(구 한국수처리기술연구회) 2017 한국수처리학회지 Vol.25 No.4

          Effects of molar ratio (x) and pH on calcium- or magnesium-aluminum layered double hydroxides (LDHs) syntheses and Cl- removal by ion-exchange with NO<sub>3</sub><sup>-</sup> in synthesized LDHs were investigated. The LDHs were synthesized under two systems such as Ca/Al-NO<sub>3</sub> (CAN) and Mg/Al-NO<sub>3</sub> (MAN). The weights of LDHs synthesized were calculated from the change of the mole of NO<sub>3</sub><sup>-</sup> removed during synthesis and compared to obtain the optimum condition. For synthesis of LDHs intercalated with NO<sub>3</sub><sup>-</sup>, the optimum molar ratios for the CAN and MAN systems were 0.25 and 0.20, respectively. The optimum pH for CAN and MAN syntheses were 11 and 10, respectively. Ion-exchange reactions of Cl- with NO<sub>3</sub><sup>-</sup> in both LDHs were finished within 10 minutes at Cl-/LDHs ratio of 0.1 (mol/mol). Increasing LDH dose led to increase linearly NO<sub>3</sub><sup>-</sup> release. However, as the dose of LDHs increased over 0.5 g/L, the NO<sub>3</sub><sup>-</sup> release was getting dominated by the dissolution of LDHs instead of ion-exchange according to mass balance analysis.

        • KCI등재

          혐기성 암모니아 산화에 대한 아질산과 질산염의 영향

          김홍태 ( Hong Tae Kim ),오상화 ( Sanghwa Oh ) 한국수처리학회 2015 한국수처리학회지 Vol.23 No.5

          Ammonium can be converted to dinitrogen gas under anaerobic conditions with nitrite as the electron acceptor. However, in nature and in wastewater treatment plants, the nitrate is generally measured, not nitrite. In this study, the anaerobic ammonium oxidation (anammox) coupled with nitrite or nitrate was investigated and the results were compared each other. Anammox microbes adaptation was passed through three phases such as endogenous denitrification, lag phase, and anammox activation phase. Anammox microbes adapted to NO2- have better results than that adapted to NO3- in aspects of the revelation period, TN removal efficiencies, and energy generation. We concluded that the anammox microbes could also utilize nitrate as the electron acceptor without combination of other nitrate reduction.

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