Clostridium Cellulolyticum H10이 첨가된 중은 혐기성소화조에서 우분뇨나 폐수슬러지 기질로부터의 증가된 메탄생성

정석희 ( Sok Hee Jung ) 한국수처리학회 2012 한국수처리학회지 Vol.20 No.6

Anaerobic digestion is an effective technology for wastewater treatment and energy recovery. Lots of effort has been made to improve performance and stability of anaerobic digesters by modifying digester architecture or optimizing digester parameters. Deliberately modifying the microbial community offers an altemative approach for improving digester performance, and several bioaugmentation tests were successfully demonstrated for this purpose. Syntrophic association in methanogenesis has been emphasized because a number of trophic groups affect the end-point methanogens. We hypothesized that cellulose hydrolysis and subsequent fermentation of monomers to methanogen-compatible substrates is a rate and extent-limiting factor in wastes with a significant cellulose fraction. The hypothesis was tested in bench-scale fed-batch reactors with amendment of the mesophilic cellulose-degrading Clostridium cellulolyticum H10, which degrades cellulose into hydrogen, acetate, and ethanol, all of which are expected to directly or indirectly enhance methanogenesis. The tested waste materials included cattle manure and wastewater sludge. Amendment with C.cellulolyticum resulted in a significant enhancement of methane, 20-30% of average increase in a significant enhancement of methane, 20-30% of average increase in cattle manure digesters and 10-20% of average increase in sludge digesters during the openration time.

미생물 연료 전지의 성능 및 전기화학에 대한 선형과 망형의 산화전극의 집전체의 영향

김준혁(Jun-Hyuk Kim),정석희(Sok-Hee Jung) 유기성자원학회 2019 유기성자원학회 학술발표대회논문집 Vol.2019 No.2019

Microbial fuel cell (MFC) is remarkable environmental and energy system that converts energy in wastewater into electrical energy and purify wastewater. There are a number of challenges for the practical implementation of MFC as a wastewater treatment process. Among them Carbon-based material is commonly used for anodes in MFCs, but its low conductivity often limits anodic performance. Application of corrosion-resistive current collector to carbon-based anode can be a promising strategy for increasing the anodic performance. In this study, it was hypothesized increasing metal current collector improved anodic performance. Two different carbon-felt anodes with stainless steel mesh (CF-M) or titanium wires (CF-W) as a current collector were tested in a single chamber MFC. In the short-term tests such as polarization and impedance tests, CF-M with the larger current collector area (21.7 cm 2 ) had 33% higher maximum power (2,311 mW/m 2 ), 81% lower anodic resistance (3 Ω), and 92% lower anodic impedance (1.1 Ω). However, in the long-term tests, CF-W with the smaller current collector area (0.6 cm 2 ) showed higher performance in power and current generation, COD removal, and CE (51%, 10%, 11%, and 5%)higher, respectively) and produced 41% higher net current in cyclic voltagramm (20.0 mA vs. 14.2 mA). This result shows that larger current collector is advantageous in short-term performance and disadvantageous in long-term performance.

환원 그래핀 옥사이드를 이용한 미생물 연료 전지 환원전극의 전기화학적 성능

구본영(Bon-Young Koo),정석희(Sok-Hee Jung) 유기성자원학회 2019 유기성자원학회 학술발표대회논문집 Vol.2019 No.2019

Activated carbon (AC) is an inexpensive catalyst for oxygen reduction in an air cathode of microbial fuel cells (MFCs). In the AC-based cathode, carbon black (CB) is used as a conductive supporting material. In this study, it was hypothesized cathodic performance would increase if reduced graphene oxide (rGO) replaces CB in an optimum ratio. rGO replaced CB in the four different weight ratios. Maximum power density was the best in rGO15 (2,642 mW/m 2 ) followed by rGO5 (2,142 mW/m 2 ). In the optimum external resistance operation, rGO5 and rGO showed similar power (~1,060 mW/m 2 ), higher than the others. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy also showed that the optimal rGO additions improved cathodic performance and reduced cathodic internal resistance. Due to the flatter and wider shape of rGO and 5 times higher electrical conductivity than CB, the rGO addition improved the cathodic performance, but the complete replacement of CB with rGO decreased the cathodic performance due to the increased thickness and the morphological crack. The optimum rGO addition is a simple and effective method for improving cathodic performance.

단일 챔버 미생물 연료 전지에서 상호 전환 계수를 사용하여 재현 가능한 분극 시험 방법 및 전기화학적 공정한 평가

손성훈(Sung-Hoon Son),정석희(Sok-Hee Jung) 유기성자원학회 2019 유기성자원학회 학술발표대회논문집 Vol.2019 No.추계

A polarization test is the most commonly used method for diagnosing microbial fuel cell (MFC) performance. Reproducible measurement method and fair assessment are very important to draw significant information; however, they have not been conducted in the MFC field. For a reproducible polarization method and fair assessment of the MFC, diverse external resistance change (ERC) and linear sweep voltammetry (LSV) polarization methods were conducted using duplicate single chamber MFCs along with other routine tests in this study. The 3-hour optimum external resistance operation followed by the 2-hour open circuit time prevented power overshoots. When a faster polarization method is used, polarization results were more reproducible, whereas power and current densities increased and polarization and optimum resistances decreased. Because performance comparison is fair and valid when it comes to a same polarization method, interconversion factors among different polarization methods were generated by using our polarization data, which were accurately measured and verified. The interconversion factors were successfully applied to the real data sets. Operational maximum power densities were provided in this study because maximum power density from any polarization test is always overestimated. It was found that the higher coulombic and energy efficiencies were attributed to lower systematic internal resistance and high anode performance. It was also found that 90% of the total cell impedances were charge transfer impedance. Impedance and polarization tests show that the cathodic resistances were 2-3 time larger than the anodic resistances. Initial voltage drops and rise during the cell operation were related with the cathode performance deterioration.

미생물 연료전지 내의 전류 포집기 면적 증가에 따른 산화 전극 성능 개선

채형원(Hyung-Won Chai),정석희(Sok-Hee Jung) 유기성자원학회 2019 유기성자원학회 학술발표대회논문집 Vol.2019 No.추계

Microbial fuel cell (MFC) is environmental energy system that convert the energy contained in organic wastewater into electrical energy by microbial catalysis. High-performance electrode materials make it possible to achieve high power generation of MFC systems by reducing internal resistance. The performance impact of the anode current collector area in the MFC was investigated in this research. Carbon-based materials are generally used for the MFC anode electrode, but their conductivity is much lower than metal materials. In this study, it was hypothesized increasing metal current collector areas improve anodic performance. Carbon-felt anodes with titanium wires or stainless steel mesh were tested. In conclusion, in the IV polarization test, maximum power density, maximum current density and optimum current density were 33%, 34% and 30% higher in CF-M (2,311 mW/m 2 , 16, 815 mA/m 2 and 7,651 mA/m 2 )than CF-W(1,737 mW/m 2 , 12,566 mA/m 2 and 5,874 mA/m 2 ), respectively. However the stainless steel mesh used as the current collector of CF-M inhibits microbial growth and adhesion on the carbon felt and reduces mass transfer because it decreases the surface area of carbon felt.

퇴적물을 이용한 미생물연료전지에서 산화전극에 따른 전력생산비교

윤미화 ( Mi Hwa Yoon ),정석희 ( Sok Hee Jung ),이승목 ( Seung Mok Lee ),양재규 ( Jae Kyu Yang ) 한국수처리학회 2011 한국수처리학회지 Vol.19 No.3

Because sediment microbial fuel cells (SMFCs) utilize organic materials and microbial catalysts in river or oceanic sediment for electricity generation, high sustainability can be ensured in SMFC operation. However, oligotrophic sediment often creates limitation of electron donor (i.e., organic matter). It results in low power production and poor sustainability of SMFCs. The objective of this study is to evaluate electricity generation using sacrificial magnesium anodes and graphite anodes with or without chitin addition in SMFCs. During 40 days, maximum power densities of magnesium, graphite, magnesium and chitin, and graphite and chitin were 1100, 0, 1575 and 2 ㎽/㎡, respectively. The combination of magnesium and chitin produced the highest power, followed by magnesium electrode, showing combined electrochemical reactions from magnesium corrosion and chitin oxidation increased electricity generation by 30%. A magnesium electrode supplemented with chitin was more slowly corroded than the magnesium alone because chitin addition slowed magnesium corrosion. It shows strict oligotrophic condition of sediment, suggesting necessity of substrate addition in SMFCs. The power level obtained in our experiment using magnesium and chitin was enough for operating oceanographic instruments, which can be possibly deployed in the coastal ocean.

역전기투석 스택의 유량에 따른 미생물 역전기투석 셀의 전기화학적 성능

트란 비엣 호아 흐엉(Viet Hoa Huong Tran),정석희(Sok-Hee Jung) 유기성자원학회 2019 유기성자원학회 학술발표대회논문집 Vol.2019 No.2019

An MRC is a bioelectrochemical system combining a microbial fuel cell (MFC) with a RED stack to generate electricity from salinity gradient and organic wastewater with simultaneous treatment. Operating an MRC at an optimum flowrate to RED is important because it is closely related with energy production rate and economic feasibility. However, influence of RED flowrates on MRC electrochemistry and power production have not been investigated. For this purpose, four different flowrates of high concentration and low concentration solutions were tested. Maximum power density was highest in 10 mL/min (3.71 W/m 2 ) and optimum current density was highest in 7.5 mL/min (5.36 A/m 2 ). By mere increasing the flowrate to MRC, maximum power and optimum current densities increased by 17.7% and 16.2%. EIS showed that impedances of anode, cathode and full-cell were decreased by 51%, 31% and 19%, respectively. Anode CV showed that peak current density was increased by 25.7%. COD removal and CE were not affected by RED flowrate. Power generation at 7.5 mL/min and 10 mL/min were not so different, but current production was better at 7.5 mL/min. Therefore, considering energy production, the RED flowrate of 7.5 mL/min is a reasonable choice for MRC operation.