• Biotechnology and Bioprocess Engineering:BBE
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• 제8권1호
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• pp.23-31
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• 2003

A mathematical model was formulated to simulate the long-term performance of an anaerobic bioreactor designed to digest Korean food wastes. The system variables of various decomposition steps were built into the model, which predicts the temporal characters of Solid waste, and volatile fatty acid (VFA) in the reactor, and gas production in response to various input loadings and temperatures. The predicted values of VFA and gas production were found to be in good agreement with experimental observations in batch and repeated-input systems. Finally, long-term reactor performance was simulated with respect to the seasonal temperature changes from 5C in winter to 25C in Summer at different food waste input loadings. The simulation results provided us with information concerning the success or failure of a process during long-term operation .

• 한국물환경학회지
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• 제36권1호
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• pp.55-68
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• 2020

Because of the intensified environmental problems such as climate change and resource depletion, sewage treatment technology focused on energy management has recently attracted attention. The conversion of primary sludge from the primary sedimentation tank and excessive sludge from the secondary sedimentation tank into biogas is the key to energy-positive sewage treatment. In particular, the primary sedimentation tanks recover enriched biodegradable organic matter and anaerobic digestion process produces methane from the organic wastes for energy production. Such technologies for minimizing oxygen demand are leading the innovation regarding sewage treatment plants. However, sewage treatment facilities in Korea lack core technology and operational know-how. Actually, the energy potential of sewage is higher than sewage treatment energy consumption in the sewage treatment, but current processes are not adequately efficient in energy recovery. To improve this, it is possible to apply chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), and anaerobic membrane bioreactor (AnMBR) to the primary sedimentation tank. To maximize the methane production of sewage treatment plants, organic wastes such as food waste and livestock manure can be digested. Additionally, mechanical pretreatment, thermal hydrolysis, and chemical pretreatment would enhance the methane conversion of organic waste. Power generation systems based on internal combustion engines are susceptible to heat source losses, requiring breakthrough energy conversion systems such as fuel cells. To realize the energy positive sewage treatment plant, primary organic matter recovery from sewage, biogas pretreatment, and co-digestion should be optimized in the energy management system based on the knowledge-based operation.

• 한국분무공학회지
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• 제15권4호
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• pp.195-201
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• 2010

Due to its carbon-neutral nature, biogas generated from anaerobic digestion or fermentation of biodegradable wastes is one of the important renewable energy sources to reduce global warming. It is mainly composed of methane and various inert gases such as $CO_2$ and $N_2$, and the actual composition of biogas significantly varies depending on the origin of anaerobic digestion process. Therefore, in order to effectively utilize this fuel as an energy source for electricity, it is important to develop power generation engines which can successfully apply biogas with significant composition variations. In this study, efforts have been made to develop a diesel-biogas duel fuel engine as a way to achieve such a stable power generation. The effects of diesel fuel injection quantity and pressure on stable combustion and engine performance were investigated, and an impact of diesel fuel atomization was discussed. The engine test results show that there exists a 2 stage combustion which consists of diesel pilot fuel burning and premixed biogas/air mixture burning in dual fuel engine operation and optimum diesel injection parameters were suggested for biogases with various compositions and heating values.

• 한국농공학회논문집
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• 제63권3호
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• pp.35-45
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• 2021

Digestate or slurry produced from anaerobic digestion is mostly applied to crop lands for its disposal and recovering nutrients. However, minimizing nitrogen losses following field application of the digestate is important for maximizing the plant's nitrogen uptake and reducing environmental concerns. This study was conducted to assess the effects of three different biogas digestate application techniques (sawdust mixed with digestate (SSD), the hole application method (HA), and digestate injected in the soil (SD)) on nitrate leaching potential in the soil. A pot laboratory experiment was conducted at room temperature of 25 ± 2 ℃ for 107 days. The experimental results showed that sawdust application method turned out to be appropriate for quick immobilization of surplus N in the form of microbial biomass N, reflecting its lower total nitrogen and NH₄-N contents and low pH. The NH₄-N and total nitrogen fate in the soil fertilized with manure showed no statistically significant (p > 0.05) differences between the different methods applied during the incubation time under room temperature. In contrast, NO₃-N concentration indicates significant reduction in sawdust treatment (p < 0.05) compared to the control and other application methods. However, the soil sawdust mixed with digestate was more effective than the other methods, because of the cumulative labile carbon contents of the amendment, which implies soil net N immobilization.

• 유기물자원화
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• 제24권1호
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• pp.31-40
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• 2016

본 연구에서는 침출수 재순환 시스템을 적용한 중온 혐기성소화를 이용하여 음식물류 폐기물을 분해하여 메탄가스를 생산하였다. 실험은 $36^{\circ}C$로 유지되는 항온수조 내에 생물반응조와 침출수 저장조로 구성된 2개의 동일한 시스템(System A, System B)을 사용하였고, 생물반응조 하단 30 mm위에는 스크린이 있어 고액분리를 하여 침출수 저장조로 침출수를 이송하였다. 침출수 재순환은 매일 수행하였으며, 침출수 재순환 시에는 생물반응조 하단에서 침출수 저장조로 2.5 L를 30분간 이송한 뒤 다시 침출수 저장조에서 생물반응조 상부로 2.5 L를 30분간 주입하였다. 주입된 음식물류 폐기물은 수집되기 전 한 번 세척하였으며 반응조에 주입되기 전에 $36^{\circ}C$로 온도를 올렸다. System A에 49.1 g VS, System B에 54.0 g VS을 2주 간격으로 투입하였다. 저해인자로 측정된 항목은 $NH_4{^+}-N$과 염도였으며, 두 가지 항목의 농도 모두 시스템에 끼친 영향은 없는 것으로 나타났다. System A는 112일간, System B는 140일 동안 운전하였는데, 각 시스템에서 인발된 슬러지는 없었다. 음식물류 폐기물의 혐기성 소화를 통한 평균 메탄 발생량은 System A의 경우 0.439 L $CH_4/g$ VS, System B의 경우 0.368 L $CH_4/g$ VS로 나타났다.

• 유기물자원화
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• 제23권2호
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• pp.28-35
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• 2015

본 연구에서는 학교 식당에서 배출되는 음식물류 폐기물을 준 회분식 액순환 건식 혐기성 소화를 이용해서 메탄가스를 생산하였다. 두 시스템이 운전되었는데, 각 시스템은 생물반응조와 액 저장조로 구성되었다. 각 생물반응조 바닥은 스크린이 설치되어 있어 2.5L의 분리된 액체는 액 저장조로 30분 동안 이송되고 이송이 끝나자마자 이송된 액은 반응조 상부로 투입된다. 이 같은 순환은 고농도의 VFAs를 가지는 액체를 반응조 상부로 공급하는 역할을 한다. 실험 초기에는 음식물류 폐기물/식종 미생물의 부피 비는 2:8이고 이는 9g VS/L의 유기물 부하로 나타낼 수 있다. 음식물류 폐기물 투입은 2주에 한번이었고, 평균 수분, 휘발물질, 회성분은 각각 65.91%, 32.73%과 1.36%로 파악되었다. 두 개의 고형물 부하가 연구되었는데, 각각 3.51g VS/d (System A)와 3.86g VS/d(System B)이다. 음식물류 폐기물 당 메탄 발생량은 각각 $6.30m^3CH_4/kgVS{\cdot}d$(System A)와 $4.94m^3CH_4/kgVS{\cdot}d$(System B)이다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권3호
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• pp.199-204
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• 2006

The purpose of this work was to evaluate the development of the anammox process by the use of granular sludge selected from a digestion reactor as a potential seed source in a lab-scale UASB (upflow anaerobic sludge blanket) reactor system. The reactor was operated for approximately 11 months and was fed by synthetic wastewater. After 200 days of feeding with $NH_4^+\;and\;NO_2^-$ as the main substrates, the biomass showed steady signs of ammonium consumption, resulting in over 60% of ammonium nitrogen removal. This report aims to present the results and to more closely examine what occurs after the onset of anammox activity, while the previous work described the start-up experiment and the presence of anammox bacteria in the enriched community using the fluorescence in situ hybridization (FISH) technique. By the last month of operation, the consumed $NO_2^--N/NH_4^+-N$ ratio in the UASB reactor was close to 1.32, the stoichiometric ratio of the anammox reaction. The obtained results from the influent-shutdown test suggested that nitrite concentration would be one key parameter that promotes the anammox reaction during the start-up enrichment of anammox bacteria from granular sludge. During the study period, the sludge color gradually changed from black to red-brownish.

• 대한환경공학회지
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• 제30권12호
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• pp.1231-1238
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• 2008

본 연구에서는 실험실 규모 2상 혐기성 소화를 이용하여 음식물 쓰레기 탈리액의 처리성을 평가하였다. 이를 위해 산발효조의 적정 유입 pH 및 HRT를 도출하고, 산발효조로의 메탄조 유출수 반송 효과, 메탄발효조에서 고형물 내부반송 및 온도의 영향을 파악하였다. 산발효조에서는 유입 pH 6.0, HRT 2일인 조건에서 메탄조 유출수 반송 후 산생성 및 VS 제거효율은 30% 및 40%에서 안정적으로 유지되었다. 유기물 부하 7 g COD/L/d 이하의 조건에서 고형물 내부반송에 의해 중온 및 고온메탄발효조의 유출수 SCOD는 반송 이전보다 낮거나 같은 수준으로 유지되었고 유기물 부하 증가에 따른 비메탄생성량(specific methane production, SMP)의 감소폭이 줄어들었다. 고형물 내부반송 이후 동일한 유기물 부하에서 COD 제거효율과 SMP는 중온메탄발효조가 고온보다 우수하였으며 이는 중온메탄발효조의 MLVSS 농도가 고온보다 높기 때문인 것으로 판단되었다. 따라서 고온산발효-중온메탄발효로 구성된 시스템이 고온산발효-고온메탄발효보다 COD 제거와 메탄발생면에서 우수한 것으로 나타났다.

• 대한환경공학회지
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• 제34권3호
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• pp.155-161
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• 2012

본 연구에서는 고순도 메탄을 회수하기 위해서 Plug Flow Reactor와 External $CO_2$ Stripper를 결합한 중온 Methane Enhancement System을 개발하였다. 반응조 운전인자로서 알칼리도와 Leachate 순환율(LRR, Leachate Recycle Rate)이 바이오가스의 조성과 생성량 및 TVS 제거효율에 미치는 영향을 규명하였다. 고순도 메탄회수 공정 운전결과 OLR 2 g TVS/L-d, 알칼리도 4 g/L as $CaCO_3$, Leachate 순환율 3 v/v-d일 때 평균 94%의 높은 메탄함량을 나타내 고순도 메탄회수를 위한 최적조건임이 밝혀졌다. 이때 1일 반응조 단위 부피당 0.71부피의 메탄이 생성되었으며, TVS 제거율은 79%로서 Control Reactor의 94% 수준을 달성하였다.

• 상하수도학회지
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• 제10권2호
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• pp.104-116
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• 1996

Anaerobic digestion is generally used for the treatment of volatile organic solids such as manure and sludge from waste water treatment plants. However, the reaction rate of anaerobic process is slow, and thus it requires a large reactor volume. To minimize such a disadvantage, physical and chemical pre-treatment is generally considered. Another method to reduce the reactor size is to adopt different reactor system other than CSTR. In this paper, the effects of heat pre-treatment and reactor configurations on the anaerobic treatability of volatile solids was studied. Carrot, kale, primary sludge, and waste activated sludge was chosen as the test materials, and the BMP method was used to evaluate the maximum methane production and first order rate constants from each sample. After the heat treatment at $130^{\circ}C$ for 30min., the measured increase in SCOD per gram VS was up to 394 mg/L for the waste activated sludge. However, the methane production potential per gram VS was increased for only primary and waste activated sludge by 17-23%, remaining the same for carrot and kale. The overall methane production process for the tested solids can be described by first order reactions. The increased in reaction constant after heat pre-treatment was also more significant for the primary and waste activated sludge than that for carrot and kale. therefore, the heat pre-treatment appeared to be effective for the solids with high protein contents rather than for the solids with high carbohydrate contents. Among the four reactor systems studied, CSTR, PFR, CSTR followed by PFR, and PFR with recycle, CSTR followed by PFR appeared to be the best choice considering methane conversion rate and the operational stability.