• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.5
• /
• pp.304-311
• /
• 2012

Chlorinated ethylenes such as perchloroethylene (PCE) and trichloroethylene (TCE) are widely used as industrial solvents and degreasing agents. Because of improper handling, these highly toxic chlorinated ethylenes have been often detected from contaminated soils and groundwater. Biological PCE dechlorination activities were tested in bacterial cultures inoculated with 10 different environmental samples from sediments, sludges, soils, and groundwater. Of these, the sediment using culture (SE 2) was selected and used for establishing an efficient PCE dechlorinating enrichment culture since it showed the highest activity of dechlorination. The cathode chamber of bioelectrochemical system (BES) was inoculated with the enrichment culture and the system with a cathode polarized at -500 mV (Vs Ag/AgCl) was operated under fed-batch mode. PCE was dechlorinated to ethylene via TCE, cis-dichloroethylene, and vinyl chloride. Microbial community analysis with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) showed that the microbial community in the enrichment culture was significantly changed during the bio-electrochemical PCE dechlorination in the BES. The communities of suspended-growth bacteria and attached-growth bacteria on the cathode surface are also quite different from each other, indicating that there were some differences in their mechanisms receiving electrons from electrode for PCE dechlorination. Further detailed research to investigate electron transfer mechanism would make the bioelctrochemical dechlorination technique greatly useful for bioremediation of soil and groundwater contaminated with chlorinated ethylenes.

• Applied Chemistry for Engineering
• /
• v.23 no.3
• /
• pp.297-301
• /
• 2012

Microbial fuel cell (MFC) is the major of bio-electrochemical system which can convert biomass spontaneously into electricity through the metabolic activity of the microorganisms. In this study, we used an activated sludge as a microbial inoculum and then investigated the feasibility of using dairy wastewater as a possible substrate for generating electricity in MFC. To examine the performance of MFC as power generator, the characteristics on cell potentials, power density, cyclic voltammetric analysis and sustainable power estimation were evaluated for dairy wastewater. The maximum power density of $40\;mW/m^2$was achieved when the dairy wastewater containing 2650 mg/L COD was used, leading to the removal of 88% of the COD. The results from this study demonstrate the feasibility of using MFC technology to generate electricity while simultaneously treating dairy wastewater effectively.

• The Microorganisms and Industry
• /
• v.17 no.2
• /
• pp.18-21
• /
• 1991

생물은 자기 복제를 통한 생장이나 생명유지를 위해 에너지를 필요로 한다. 화학영양생물은 화학에너지를 발효 혹은 호흡을 통해 생물학적 에너지로 전환시키며, 광영양생물은 광합성 작용을 통해 광에너지를 이용한다. 발효, 호흡, 광합성은 모두 산화-환원 반응을 통해 이루어진다. 생물의 모든 에너지 전환반응은 산화-환원 반응, 즉 전자의 흐름으로 이루어지며 생명현상이 에너지를 필요로 하기 때문에 생명현상은 전자의 흐름으로 이루어진다고 할 수 있다. 모든 생물이 에너지 전환 반응에 산화-환원 반응을 이용한다는 말은 생물이 많은 종류의 산화-환원 효소를 보유하고 있다는 뜻이며, 실제 많은 종류의 산화-환원 효소가 발견되고 연구되었다.

• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.2
• /
• pp.82-88
• /
• 2017

MET (Microbial Electrochemical Technology), such as MFC (Microbial Fuel Cell) and MEC (Microbial Electrolysis Cell), is a promising technology for producing sustainable biogas from an anaerobic digester (AD). At current stage, however, the most likely limiting factors, large internal resistances, should be overcome for successful scale up of this technology. Various researchers reported that application of electrode materials containing high current density, increase of ion strength and conductivity, configuration of electrode are good methods for minimizing internal resistances. Recently, stainless steel is receiving great attention because of not only high performance and durability but also low cost. Therefore, in this study, we evaluate electrochemical characteristics and biogas production rate using various electrode materials and configuration (graphite carbon coated with catalysts ($GC-C_M$) or not (GC), stainless steel mesh (SUS-M) and plate (SUS-P)). As the results, current densities of $GC-C_M$, GC, SUS-P, SUS-M were 2.03, 1.36, 1.04, $1.13A/m^2$, respectively. Methane yields of $GC-C_M$, GC, SUS-P, SUS-M were 0.27, 0.14, 0.19, 0.21 $L-CH_4/g-COD_{rem}$., respectively. Stainless steel shows high current density and methane yield, which are similar as graphite carbon coated with catalysts.

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.9
• /
• pp.692-700
• /
• 2011

The use of electric field has been studied as an alternative for biofilm control dominated by disinfectants and antibiotics. This technology would be advantageous in the environmental respect that biofilm can be controlled based on electron transfer, not using chemical disinfectants and antibiotics. Control mechanisms which were reported by earlier studies are organized as; (1) bacterial adhesion control by electrostatic repulsion at a negative current, (2) bacterial adhesion control using bacterial motion and (3) bacterial inactivation by direct oxidation at a positive current, (4) bioelectric effect leading to biofilm inactivation. In this review article, we summarized the technologies for biofilm control using electric field and provided some application examples from previous studies.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.4
• /
• pp.201-209
• /
• 2016

Theoretical maximum methane yield of glucose at STP (1 atm, $0^{\circ}C$) is 0.35 L $CH_4/g$ COD. However, most researched actual methane yields of anaerobic digester (AD) on lab scale is lower than theoretical ones. A wide range of them have been reported according to experiments methods and types of organic matters. Recent year, a MET (Microbial electrochemical technology) is a promising technology for producing sustainable bio energies from AD via rapid degradation of high concentration organic wastes, VFAs (Volatile Fatty Acids), toxic materials and non-degradable organic matters with electrochemical reactions. In this study, methane yields of food waste leachate and sewage waste sludge were evaluated by using BMP (Biochemical Methane Potential) and continuous AD tests. As the results, methane production volume from the anaerobic digester equipped with MET (AD + MET) was higher than conventional AD in the ratio of 2 to 3 times. The actual methane yields from all experiments were lower than those of theoretical value of glucose. The methane yield, however, from the AD + MET occurred similar to the theoretical one. Moreover, biogas compositions of AD and AD + MET were similar. Consequently, methane production from anaerobic digester with MET increased from the result of higher organic removal efficiency, while, further researches should be required for investigating methane production mechanisms in the anaerobic digester with MET.

• Journal of Korean Society of Water and Wastewater
• /
• v.34 no.5
• /
• pp.345-356
• /
• 2020

The removal of organic carbon and nutrients (i.e. N and P) from wastewater is essential for the protection of the water environment. Especially, nitrogen compounds cause eutrophication in the water environment, resulting in bad water quality. Conventional nitrogen removal systems require high aeration costs and additional organic carbon. Microbial electrochemical system (MES) is a sustainable environmental system that treats wastewater and produces energy or valuable chemicals by using microbial electrochemical reaction. Innovative and cost-effective nitrogen removal is feasible by using MESs and increasing attention has been given to the MES development. In this review, recent trends of MESs for nitrogen removal and their mechanism were conclusively reviewed and future research outlooks were also introduced.

• Applied Chemistry for Engineering
• /
• v.20 no.2
• /
• pp.213-217
• /
• 2009

Microbial fuel cells (MFCs) have been known as a new alternative energy conversion technology for treating wastewater and producing electricity simultaneously. A MFC converts the chemical energy of the organic compounds to electrical energy through microbial catalysis at the anode under anaerobic conditions. To examine the performance of MFC, in this work, the characteristics of the efficiency of wastewater treatment and generation of electricity was evaluated for sewage. When acetate as a carbon source was added into the sewage, the removal efficiency of COD was increased from 75.7% to 88.2% and the voltage was increased significantly from 0.22 V to 0.4 V. The influence of distance between anode and cathode was examined and the effect of the surface area of anode was investigated under the various external resistances. It was found that the maximum power density was $610mW/m^2$ and power generation was effective when the distance between the electrodes was shorter and the surface area of the anode was smaller.

• Proceedings of the KAIS Fall Conference
• /
• 2010.11a
• /
• pp.482-482
• /
• 2010

하수처리장에서 발생하는 유기성 슬러지는 대부분 해양투기에 의해 처분되고 나머지는 매립, 소각, 퇴비화 등으로 처분된다. 그러나 런던협약 '96 의정서' 발효에 의해 2012년부터 해양투기가 금지되고, 매립장 및 소각장의 신규건설은 님비(NIMBY) 현상에 의해 제한받기 때문에 효과적인 슬러지 처분 및 가용화 방법이 요구되고 있다. 현재 초음파[1]나 열처리[2], 오존[3,4], 미생물 처리[5,6] 등 물리, 화학, 생물학적 처리방안이 연구되고 있으나 이러한 방법들은 에너지 과소비, 2차 오염물질 발생에 따른 처리비용 증가 등의 단점을 가지고 있다. 따라서 본 연구에서는 기존의 연구 방법을 보안하고자 전기분해를 활용하여 슬러지 가용화를 시도함으로써 슬러지 발생을 저감시킬 수 있는 방법을 연구하였다. 본 실험에서는 전기분해를 위해 제작된 불용성 전극은 Titanium에 Iridium을 코팅하여 제작하였고, 최대 20V까지 전압을 고정시키고 시간에 따라 변화되는 전류와 전기전도도, pH 값을 관찰하였다. 실험에 사용된 활성슬러지는 3개월간 합성폐수로 순응화 시킨 후에 시료로 사용하였다. 전기분해에 의해 처리된 활성슬러지의 여액을 분석한 결과 SCOD, TN, TP 농도가 각각 510%, 9%, 106% 증가하였다. 이는 전기분해에 의해 미생물의 세포벽이 파괴되어 세포 내 물질들이 세포 외부로 용출되어 미생물들의 이용이 가능한 상태로 되었음을 알 수 있었다. 이는 국내 하 폐수의 낮은 C/N비 때문에 무산소조에 메탄올 같은 외부 탄소원을 공급하는 대신에 별도의 탄소원 공급 없이 가용화 된 슬러지를 반송시킴으로써 슬러지 저감에 따른 폐기 비용과 운전비용의 절감을 기대할 수 있어, 근본적인 슬러지 발생을 저감시킬 수 있는 해결책이라 할 수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.8
• /
• pp.5728-5735
• /
• 2015

This study attempts to verify the applicability of ceramic membrane as a separator by comparing the power generation characteristics in single-chamber MFCs using ceramic membranes to those in the MFCs using nafion membrane. The generated power in MFCs by using acetate as a substrate was more stable than that by using formate, propionate and butyrate, respectively. It was shown that the generated power by using formate substrate in MFCs was unstable and a little higher than that by using acetate, and the power generated by using propionate and butyrate were lower than that by using acetate. In order to find out the Pt catalyst effect, it was compared the power generated in MFCs using Pt-coated carbon cloth as electrode to that power using normal carbon cloth. The power generated in MFCs using Pt-coated carbon cloth as electrode was 1.2 times higher than that using normal carbon cloth. The Pt-coated carbon cloth was about 5 times more expensive than normal carbon cloth. It is suggested that both power generation efficiency and cost together should be considered in selecting electrodes of MFCs. It was found that the ceramic membrane was superior to nafion membrane by comparing to the power generation characteristics obtained. It was shown that average voltage values were $523.67mV{\pm}49.41mV$ by using synthetic wastewater, in MFCs of ceramic membrane as a separator. While average voltage values were $424.09mV{\pm}79.95mV$ by using synthetic wastewater, in MFCs of nafion membrane as a separator. The organic removal efficiency, 41.7% by using ceramic membrane was a little bit higher than 40.8% by using nafion membrane. This research implies ceramic membrane can be a valid alternative to nafion membrane as a separator when considering the power generation and the efficiency of organics removal.