• Journal of Microbiology and Biotechnology
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• v.6 no.1
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• pp.30-35
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• 1996

Distillery wastewater was used in a thermophilic laboratory-scale two stage anaerobic digester to test the effects of the redox potential of the first acidogenic reactor on the performance of the system. The digester consisted of first a acidogenic reactor and the an upflow anaerobic sludge blanket (UASB) reactor. The digestor was operated at a hydraulic retention time (HRT) of 48 h. Under these conditions, about 90% of the chemical oxygen demand as measured by the chromate method ($COD_{cr}$) was removed with a gas production yield of 0.4 l/g-COD removed. The redox potential of the acidogenic reactor was increased when the reactor was purged with nitrogen gas or agitation speed was increased. The increase in reduction potential was accompanied by an increase in acetate production and a decrease in butyrate formation. A similar trend was observed when a small amount of air was introduced into the acidogenic reactor. It is believed that the hydrogen partial pressure in the acidogenic reactor was decreased by the above mentioned treatments. The possible failure of anaerobic digestion processes due to over-loading could be avoided by the above mentioned treatments.

• Journal of environmental and Sanitary engineering
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• v.15 no.4
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• pp.84-90
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• 2000

5L laboratory-scale anaerobic digester was used to study the effects of food size and washing rate of food waste on the mixed digestion with sewage sludge. Food waste was crushed with particle diameters of 4mm and 2mm and washed two to three times, and seven to eight times before feeding the batch digester. The digester with crushed of washed food waste showed better performance than that with uncrushed of unwashed to produce methane gas of reduce volatile solids. The digester with 2mm food waste showed 17.4% higher VS/TS reduction rate and 18ml higher methane production rate per gram VS input than that with uncrushed food waste, where VS and TS are volatile solid and total solids in the liquid effluent, respectively. Also food waste crushed eight times gave 8% higher VS/TS reduction rate and 11ml higher methane production rate per gram VS input than unwashed food waste.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.23-32
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• 1982

This study was conducted to evaluate the temperature effects on the nightsoil, anaerobic digestion, whether it could be operated with a higher organic loading rate at a higher temperature during summer months, or with a lower organic loading rate at a lower temperature during winter months. A laboratory completely mixed digester was continuously operated at 11 different temperatures from $18.5^{\circ}$ to $60^{\circ}C$ with 30 days of HRT. The study results indicated that the best efficiency occurred at a temperature range of $35^{\circ}$ to $40^{\circ}C$, at which BOD and VS removal efficiencies were respectively 71 and 53 percent, and gas production rate was $0.6m^3/kg$ VS fed or $16m^3/m^3$ fed. BOD removal efficiency would be increased to 78 percent if the digester effluent settled for 24 hours. Since the digester efficiency decreased beyond this temperature range, this suggested the digester need not to operate a higher temperature even during the summer months. The laboratory results were in good agreement with those of the existing digester operated at a temperature range of $32^{\circ}$ to $40^{\circ}C$. Application of septage or cow manure to the digester with nights oil at a rate of 1 to 1 did not greatly affect the digester performances. In addition, the digester effluent could be treated aerobically without any dillution water. BOD and SS removal efficiencies were greater than 90 percent in this case.

• Journal of Environmental Health Sciences
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• v.25 no.3
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• pp.29-35
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• 1999

Quantity and composition of biogas from semi-continuous anaerobic digestion of straw were obtained experimentally in laboratory scale digesters fed with 1 liter of 5% straw-water mixture and maintained at 35$^{\circ}C$. Experiments were carried out for hydraulic retention time(HRT) of 8, 10 and 15days, respectively. The amount and composition of biogas produced were measured until steady-state was achieved for each run. The amount of biogas and methane percent go through a maximum and decrease continuously towards the steady-state after three times operation of hydraulic retention time(HRT). Methane gas production rates at steady-state increase with the increasing of HRT. Biogas production of 0.45 liter/day with 25% methane, 0.42 liter/day with 33.7% methane and 0.492 liter/day with 31.7% methane were obtained for 8, 10 and 15days of HRT, respectively. The high proportion of soluble carbohydrates present in straw makes the volatile fatty acids to build up within the digester causing a drop in pH that inhibits digestion. Regular control of pH is therefore necessary by adding alkalinity. Reductions in COD increase with increase in HRT. The stratification of plant material within the digester is different from that of manure, and modifications in design and operation of digesters may be necessary if they are fed with plant matter.

• Journal of Environmental Science International
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• v.1 no.2
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• pp.125-136
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• 1992

Digestion of a municipal wastewater sludge by the anaerobic sequencing batch reactor (ASBR) was investigated to evaluate the performance of the ASBR process at a critical condition of high-solids-content fined. The reactors were operated at an HRT of 10 days with an equivalent loading rate of 0.8-1.5 gVS/L/d at 35$^{\circ}C$ The main conclusions drawn from this study were as follows: 1. Digestion of a municipal wastewater sludge was possible using the ASBR in spite of high concentration of settleable solids in the sludge. The ASBRS with 3- and 4-day cycle period showed almost identical high digestion performances. 2. No adverse effect on digestion stability was observed In the ASBRS in spite of withdrawal and replenishment of 30% or 40% of liquid contents. A conventional anaerobic digester could be easily converted to the ASBR without any stability problem. 3. Flotation thickening occurred in thicken step of the ASBRS throughout steady state, and floating bed volume at the end of thicken period occupied about 70% of the working volume of the reactor Efficiency of flotation thickening in the ASBRS could be comparable to that of additional gravity thickening of a completely mixed digester. 4. Solids were accumulated rapidly in the ASBR during start-up period. Solids concentrations in the ASBRS were 2.6 times higher than that in the completely mixed control reactor at steady state. Dehydrogenase activity had a strong correlation with the solids concentration. Dehydrogenase activity of the digested flu형e in the ASBR was 2.9 times higher than that of the flu형e in the control reactor, and about 25 times higher than that of the subnatant in the ASBR. 5. Remarkable increase in equivalent gas production of 52% was observed at the ASBRS compared with the control reactor in spite of similar quality of clarified effluent from the ASBRS and control reactor. The increase in gas production from the ASBRS was believed to be combined results of accumulation of microorganisms, higher driving force applied, and additional long-term degradation of organics continuously accumulated.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.7
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• pp.516-522
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• 2011

The largest problem of domestic anaerobic digestion is low digestion efficiency. Reasons of the problem would be low organic matters input, low mixing efficiency in digestion tank, refractory excess sludge etc.. In this study, screw attached disk-type concentration system and a mechanical mixing system, solubilization facility improvements were performed to solve problems. Through these improvements, the sludge conc. of the concentrator increased 2.6-fold and the volume reduction efficiency was increased 3.0-fold. In addition, the dead-space is reduced by mechanical agitation. Anaerobic digester gas production in the digestion tank is increased from $193.8m^3$ to $386.0m^3$ per day. Digestion efficiency is improved to 54.6% from 47.6%. Digestion gas production is increased from $0.30Nm^3/kg$ VS to $0.42Nm^3/kg$ VS.

• Journal of Environmental Science International
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• v.28 no.2
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• pp.203-209
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• 2019

Organic wastewater generated from polyester manufacturing processes was selected from H company to investigate the feasibility of anaerobic digestion that produces gases including methane. Bio Methane Potential (BMP) tests were conducted to measure the gas production and methane concentration for 7 process wastewater and 2 kinds of sludges from the H company. Also, along with monitoring pH and alkalinity during the anaerobic digestion process, the concentrations of COD and 1,4-dioxane were measured with 4 different operating conditions for N Emulsion (NE) and Ethylene Glycol (EG) wastewater. The BMP tests showed that 65% of methane was produced from NE and EG wastewater. This suggests that the organic wastewater from H company can be effectively treated by an anaerobic digester by which more than 90% of COD was removed.

• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.541-554
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• 2000

Experimental study of anaerobic digestion process combined with and without the submerged separation membrane was investigated by using laboratory-scale reactor at the hydraulic retention time of 0.5 day and 1.0 day. The removal efficiencies of carbohydrate at the digester without and with membrane were 84.4 to 86.8 % and 99.6 to 99.7 %, respectively, and the methane gas recovery efficiencies were 0.4 to 1.2 % and 12.3 to 28.7 %. According to the measurement by the most probable numbers method. the numbers of various groups of bacteria in the digesters with membrane were enumerated in the following ranges ; acidogens : $1.7{\times}10^9$ to $5.0{\times}10^9MPN/m{\ell}$, homoacetogens : $5.0{\times}10^7$ to $2.4{\times}10^8MPN/m{\ell}$, $H_2$-utilizing methanogens : $1.3{\times}10^7$ to $9.2{\times}10^8MPN/m{\ell}$, and acetate-utilizing methanogens : $2.3{\times}10^6$ to $2.0{\times}10^8MPN/m{\ell}$. The number of methanogens at the digester with membrane increased by approximately $10^2$ to $10^4$ times in comparison with that of the digester without membrane.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.1
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• pp.13-19
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• 2017

Relatively low efficiency in anaerobic digestion process is mainly caused by unproper mixing method. In this study, tray motion type agitator was applied in actual anaerobic digestion tank in order to improve the digestion efficiency, equalize the flow velocity distribution and energy saving. The impeller of tray motion type agitator was reciprocated vertically. Gas lift type agitator and tray motion type agitator appears almost same mixing efficiency include digestion rates. However, tray motion type agitator have shown that lower energy consumption compared to the conventional gas lift type agitator. Implementation of tray motion type agitator in the anaerobic digestion tanks contributed to the stabilization of mixing environment, efficiency and energy efficiency of the tank.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.4
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• pp.54-62
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• 1997

Disposal of blue crab wastes represents a significant problem to processors, who are limited with respect to acceptable disposal alternatives. Anaerobic bioconversion technology was investigated to determine an environmentally sound and economic disposal method for these wastes. In the study ultimate methane yield for total crab solid waste was $0.180m^3/kg$ VS added and biodegradation rate constant was $0.15day^{-1}$. Methane yield of the bench-scale reactor operated on similar feedstock was $0.189m^3/kg$ VS added and biodegradation rate constant was $0.06day^{-1}$. These results indicate that anaerobic bioconversion of blue crab wastes was technically feasible. Use of anaerobic bioconversion technology can be an attractive option for blue crab processing waste management. The by-product methane gas could be used for maintainign a number of processing operations (i.e., heat for cooking, or keeping temperature of digester constant).