Na₂S를 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 Na₂S addition on the precipitation of heavy metals from the spent soil washing solution and thereby recycling of EDTA was investigated. Addition of Na₂S into the single metal-EDTA and the mixed metal-EDTA solutions ([Na₂S]/[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)₂ was subsequently added to induce further precipitation of Zn and Ni and to reduce the Na₂S dose. At the [Na₂S]/[metal-EDTA] ratio of 10, the removal efficiencies of all heavy metals excluding Ni were above 98% with the dose of Ca(OH)₂ at 0.002, 0.006 and 0.008 g into 100 mL of Cu-, Pb- and Zn-EDTA solutions, respectively. However, Ca(OH)₂ 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.

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 NO₃ ^- 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 NO₃-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.

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.

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.

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 (R²>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.

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.

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.

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.

알루미늄 전극을 이용한 하수내 질소, 인 제거

이경현 ( Kyunghyun Lee ),오상화 ( Sanghwa Oh ) 한국수처리학회 2023 한국수처리학회지 Vol.31 No.1

To enhance water quality standards, the removal of nitrogen (N) and phosphorus (P) has required additional chemical treatment in wastewater treatment plants. This demand has caused problems such as excessive chemical injection and an increase in the amount of sludge production. To deal with these problems, this study investigated the efficiency of electrochemical N and P removal from sewage wastewater and biologically treated water using aluminum and stainless steel (Al-SUS) electrodes in the existing sewage treatment method. The operating variables in this study are the reaction time and current density of the electrode. Overall, the longer the reaction time and the higher the current density, the greater the tendency for BOD, TN, and TP removal efficiency. However, TP concentration in effluent was ≤ 0.1 mg/L regardless of the reaction time when the current density was ≥ 5 mA/㎠, and ≤ 0.06 mg/L regardless of the current density when the reaction time was 10 min. The TN concentration in the effluent increased as the current density and reaction time increased. Furthermore, biologically treated effluent was found to be additionally removed by approximately 64-70%, up to 0.8 mg/L. Consequently, the economic current density using aluminum electrodes for TN and TP treatment from domestic wastewater was ≤ 5 mA/㎠ for a reaction time of 3 min. N and P removal process using aluminum electrodes has little impact on temperature and can be applied to the biologically treated wastewater. Therefore, the process could be implemented in small-scale wastewater treatment plants or where it is difficult to secure a large site.

Ca-Al-NO₃ 또는 Mg-Al-NO₃ 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 NO₃^- in synthesized LDHs were investigated. The LDHs were synthesized under two systems such as Ca/Al-NO₃ (CAN) and Mg/Al-NO₃ (MAN). The weights of LDHs synthesized were calculated from the change of the mole of NO₃^- removed during synthesis and compared to obtain the optimum condition. For synthesis of LDHs intercalated with NO₃^-, 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 NO₃^- in both LDHs were finished within 10 minutes at Cl-/LDHs ratio of 0.1 (mol/mol). Increasing LDH dose led to increase linearly NO₃^- release. However, as the dose of LDHs increased over 0.5 g/L, the NO₃^- release was getting dominated by the dissolution of LDHs instead of ion-exchange according to mass balance analysis.