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Membrane Bioreactor를 이용한 폭발성 물질의 가수분해 부산물의 탈질과정에의 적용
조경덕 ( Kyung Duk Zoh ) 한국물환경학회 2002 한국물환경학회지 Vol.18 No.2
A bench-scale anoxic membrane bioreactor (MBR) system, consisting of a bioreactor coupled to a ceramic crossflow ultrafiltration module, was evaluated to treat a synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX, The wastewater was formulated the same as RDX hydrolysates, and consisted of acetate, formate, formaldehyde as carbon sources and nitrite, nitrate as electron accepters. The MBR system removed 80 to 90% of these carbon sources, and approximately 90% of the stoichiometric amount of nitrate, 60% of nitrite. The reactor was also operated over a range of transmembrane pressures, temperatures, suspended solids concentration, and organic loading rate in order to maximize treatment efficiency and permeate flux. Increasing transmembrane pressure and temperature did not improve membrane flux significantly. Increasing biomass concentration in the bioreactor decreased the permeate flux significantly. The maximum volumetric organic loading rate was 0.72 kg COD/㎥/day, and the maximum F/M ratio was 0.50 kg N/kg MLSS/day and 1.82 kg COD/kg MLSS/day. Membrane permeate was clear and essentially free of bacteria, as indicated by heterotrophic plate count. Permeate flux ranged between 0.15 and 2.0 ㎥/㎡/day and was maintained by routine backwashing every 3 to 4 day. Backwashing with 2% NaOCl solution every fourth or fifth backwashing cycle was able to restore membrane flux to its original value.
Occurrence and removals of micropollutants in water environment
Moon-Kyung Kim,Kyung-Duk Zoh 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.4
Micropollutants are often discharged to surface waters through untreated wastewater from sewage treatment plants and wastewater treatment plants. The presence of micropollutants in surface waters is a serious concern because surface water is usually provided to water treatment plants (WTP) to produce drinking water. Many micropollutants can withstand conventional WTP systems and stay in tap water. In particular, pharmaceuticals and endocrine disruptors are examples of micropollutants that are detected at the drinking water, ppb, or even ppb level. A variety of techniques and processes, especially advanced oxidation processes, have been applied to remove micropollutants from water to control drinking water contamination. This paper reviews recent researches on the occurrence and removal of micropollutants in the aquatic environments and during water treatment processes.
Fate and Transport of Mercury in Environmental Media and Human Exposure
Kim, Moon-Kyung,Zoh, Kyung-Duk The Korean Society for Preventive Medicine 2012 Journal of Preventive Medicine and Public Health Vol.45 No.6
Mercury is emitted to the atmosphere from various natural and anthropogenic sources, and degrades with difficulty in the environment. Mercury exists as various species, mainly elemental ($Hg^0$) and divalent ($Hg^{2+}$) mercury depending on its oxidation states in air and water. Mercury emitted to the atmosphere can be deposited into aqueous environments by wet and dry depositions, and some can be re-emitted into the atmosphere. The deposited mercury species, mainly $Hg^{2+}$, can react with various organic compounds in water and sediment by biotic reactions mediated by sulfur-reducing bacteria, and abiotic reactions mediated by sunlight photolysis, resulting in conversion into organic mercury such as methylmercury (MeHg). MeHg can be bioaccumulated through the food web in the ecosystem, finally exposing humans who consume fish. For a better understanding of how humans are exposed to mercury in the environment, this review paper summarizes the mechanisms of emission, fate and transport, speciation chemistry, bioaccumulation, levels of contamination in environmental media, and finally exposure assessment of humans.
담수 환경에서의 미세플라스틱 검출 및 위해성 평가에 관한 고찰
김문경(Moon-Kyung Kim),조경덕(Kyung-Duk Zoh) 서울대학교 보건환경연구소 2019 보건학논집 Vol.56 No.1
Microplastics (MPs), a plastic debris with a particle diameter of less than 5 mm, are a pollutant of environmental concern and have received attention in recent years. The effects of MPs on the human body and the cause of their occurrence have not been clarified, but there is no doubt that the concentration in the natural environment surrounding human life is increasing. Therefore, it is necessary to make efforts to establish the basis of MPs investigation system and risk. In the future, various researches should be carried out in order to establish scientific basis such as investigation of source and contamination status of MPs at the national level, the degree of bioaccumulation and influence of MPs emitted into aquatic ecosystem, and the harmfulness of MPs themselves. In this study, we intended to look into other studies on the collected sampling methods, pretreatment methods, and analysis methods in order to help better understand MPs in freshwater. In addition, we reviewed relating to the potential environmental risks and impacts on MPs in the freshwater environment, and proposed the risk assessment models of MPs in freshwater environments. This study will be helpful to the future research on the monitoring system, human health risk, and development of environmental policies to manage the MPs pollution.
Effects of molecular size fraction of DOM on photodegradation of aqueous methylmercury
Kim, Moon-Kyung,Won, A-Young,Zoh, Kyung-Duk Elsevier 2017 CHEMOSPHERE - Vol.174 No.-
<P><B>Abstract</B></P> <P>This study investigated the photodegradation kinetics of MeHg in the presence of various size fractions of dissolved organic matter (DOM) with MW < 3.5 kDa, 3.5 < MW < 10 kDa, and MW > 10 kDa. The DOM fraction with MW < 3.5 kDa was most effective in MeHg photodegradation. Increasing UV intensity resulted in the increase of photodegradation rate of the MeHg in all size of DOM fractions. Higher rates of MeHg degradation was observed at higher pH. For the portion of MW < 3.5 kDa, the photodegradation rate of MeHg increased with increasing DOM concentration, indicating that radicals such as singlet oxygen (<SUP>1</SUP>O<SUB>2</SUB>) radicals can be effectively produced by DOM. At higher portion of MW > 3.5 kDa, the inhibition of MeHg degradation was observed due to the effect of DOM photo-attenuation. Our result indicates that radical mediated reaction is the main mechanism of photodegradation of MeHg especially in the presence of MW < 3.5 kDa. Our results imply that the smaller molecular weight fraction (MW < 3.5 kDa) of DOM mainly increased the photodegradation rate of MeHg.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We examined the effect of DOM in humic substances on the photodegradation of MeHg. </LI> <LI> DOM fraction of MW < 3.5 kDa showed the highest photodegradation rate of MeHg. </LI> <LI> MeHg photodegradation increased at alkaline pH due to OH radical production. </LI> <LI> Photo-degradation of MeHg increased with increasing DOM concentration. </LI> <LI> Radicals produced by DOM under MW < 3.5 kDa increased photodegradation of MeHg. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>