• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.2
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• pp.15-29
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• 2016

This study investigated the environmental and economical assessment for sewage sludge treatment options including biogasification, incineration, carbonization, drying, and solidification. Considering B/C ratio for an anaerobic digestion treatment, for $270,000m^3/d$ (over $1,150m^3/day$), B/C was 1, as the moisture content increased to 95 %, B/C was 1 for $100000m^3/d$ (capacity of $400m^3/day$). Anaerobic digestion+solidification was the most economically feasible, then Anaerobic digestion+incineration and anaerobic digestion+drying were the next economically feasible and then anaerobic digestion+carbonization was the least economically feasible. If anaerobic digestion efficiency was improved to 45%, the treatment costs for anaerobic digestion+carbonization, anaerobic digestion+incineration and anaerobic digestion+drying were decreased to 3,000~5,000 won/t and the costs for anaerobic digestion+solidification was decreased to 2,000~3,000 won/t due to increasing of the beneficial cost of the biogas production.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.413-424
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• 2014

The potential of using the biogas as energy source has long been widely recognised and current techniques are being developed to upgrade the technical quality and to enhance energy efficiency. The objective of this paper is to present efficient and effective pre-treatment methods of increasing the amount of produced biogas in anaerobic digestion of activated sludge treatment process. The paper also presents a review of the effect on biogas production between pre-treated and raw sludge, and also put forward the advantages and disadvantages of each pre-treatment method.

• New & Renewable Energy
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• v.1 no.2 s.2
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• pp.60-72
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• 2005

The effect of alkaline pre-treatment on the solubilization of waste activated sludge(WAS) was investigated, and the biodegradability of WAS, pretreated WAS, [PWAS], food waste and two types of mixture were estimated by biochemical methane potential [BMP] test at $35^{\circ}C$. The biodegradability of PWAS and mixture waste were significantly improved due to the effect of alkaline hydrolysis of WAS. An alkaline pre-treatment was identified to be one of the useful pre-treatment for improving biodegradability of WAS and mixture waste. In high-rate anaerobic co-digestion system coordinate with an alkaline pre-treatment in process, the digesters were operated at the HRT of 5, 7, 10 and 13 days with a mixture of FW $50\%\;and\;PWAS\;50\%,\;$In term of $CH_4$ content, VS removal and specific methane production [SMP] which are the parameters in the performance of digester, the optimum operating condition was found to be a HRT of 7 days and a OLR of 4.20g/L-day with the highest SMP of 0.340 L $CH_4/g$ VS.

• Journal of Environmental Health Sciences
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• v.26 no.4
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• pp.82-87
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• 2000

생물학적 슬러지를 대상으로 간헐포기 소화와 호기성 소화의 회분실험을 실시하였다. 생물학적 슬러지의 간헐포기 및 호기성 소화 초기단계에서 미생물의 감량은 주로 내생 호흡에 의해 이루어졌다. 이 단계에서 질소는 곧바로 용출되지 않고 슬러지내에 잔존함으로서 슬러지의 질소함량은 일시적으로 증가한다. 그러나 소화후반에서는 최초의 질소함량수준으로 다시 감소하였다. 34일간의 회분식 소화에서 호기성 소화의 총질소 제거효율은 0.1%로서 거의 제거가 안된 반면, 포기 비율 0.25, 05 및 0.75인 간헐포기 소화에서는 각각 42.7%, 42.5% 및 17.6%로 나타나 간헐포기 소화가 호기성 소화보다 질소 제거측면에서 우수하였다. VSS의 감소에 따라 슬러지내의 인도 수중으로 용출하였으나, 인 용출율은 VSS 감소율 보다 훨씬 낮았고 그 결과 소화슬러지의 인 함량은 지속적으로 증가하였다. 호기성 소화와 간헐포기 소화는 소화슬러지의 인 함량이 증가하는 공정이므로 반송수의 인 부하는 상대적으로 낮아지게 되고 이는 하수의 영양염류 제거측면에서 긍정적인 효과를 미칠 것으로 기대된다.

• Journal of Industrial Technology
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• v.39 no.1
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• pp.21-25
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• 2019

This work experimentally determined the effect of microaerobic condition on anaerobic digestion of thickened waste activated sludge in semi-continuous mesophilic digesters at hydraulic retention time of 20 days. The concentration of hydrogen sulfide was $7{\pm}2ppm$ at the microaerobic condition and $14{\pm}2ppm$ at the anaerobic condition. Removal efficiency of volatile solid was not significantly different between microaerobic ($40{\pm}8%$) and anaerobic ($38{\pm}8%$) conditions. There was no important difference between microaerobic ($1,352{\pm}98ml/d$) and anaerobic ($1,362{\pm}104ml/d$) conditions in the biogas production, either. Therefore, it could be concluded that the application of the microaerobic condition was an efficient method of the hydrogen sulfide removal from the biogas.

• Journal of Energy Engineering
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• v.23 no.1
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• pp.33-39
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• 2014

This study was performed with electrolysis treatment method for improving anaerobic digestion gas production efficiency in a sewage sludge, thereby confirmed in anaerobic digestion production and denitrification effect. As a result, solubilization was increased by increasing treatment time of electrolysis and current density, also showed to be 9.02% with 10 mA/cm2 of current density in 4 mm electrode distance. Based on the results of BMP test used the above experiment, methane production was 0.49 L CH4/g VS, and increased by 88.4% compared with control groups. As for the results of denitrification using the sewage sludge treated with the same conditions, denitrification rate appeared $19.2mg\;NO_3{^{-}}N/g\;MLVSS{\cdot}hr$, and through the sewage sludge treated with electrolysis, it can be applied to anaerobic digestion and denitrification process by increasing biodegradation.

• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.4
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• pp.99-106
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• 2021

The purpose of this study was to evaluate the performance of novel process with thermal hydrolysis and separation as pre-treatment of anaerobic digestion (AD). The dewatered sludge was pre-treated using THP, and then separated. The separated liquid used as substrate for AD and separated solid was returned on THP(Thermal Hydrolysis Process). The degree of disintegration (DD, based on COD) using only THP found 45.1-49.3%. The DD using THP+separation found 76.1-77.6%, which was higher than only THP. As result from dual-pool two-step model, the ratio of rapidly degradable substrate to total degradable substrate found 0.891-0.911 in separated liquid, which was higher than only THP. However, the rapidly degradable substrate reaction constant (kF) of only THP and THP+separation were similar. This results found that dewatered sludge was disintegrated by THP, and then rapidly degradable substrate of hydrolyzed sludge was sorted by separation.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.1 no.2
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• pp.125-136
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• 1997

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 feed. 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 sludge in the ASBR was 2.9 times higher than that of the sludge 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 the Korea Organic Resources Recycling Association
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• v.26 no.4
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• pp.53-61
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• 2018

Anaerobic digestion (AD) is one of the most widely used process that can convert the organic fraction of waste activated sludge (WAS) into biogas. However, most researched actual methane yields of anaerobic digester (AD) on lab scale is lower than theoretical ones. Bioelectrochemical, anaerobic digester was used to increase methane yield from waste activated sludge. The influence of anaerobic digestion sludge and raw sludge mixing ratio (3:7, 5:5) on methane yield and organic matter removal efficiency were explored. As a result, when the mixing ratio of bioelectrochemical anaerobic sludge was 5:5 compared with 3:7, the highest methane yields were 294.2 mL $CH_4/L$ (0.63 times increase) and 52.5% (7.5% increase), the bioelectrochemical anaerobic digester(5:5) was more stable in the pH, t otal alkalinity and VFAs, respectively. These results showed that the increase in the mixing ratio of anaerobic digestion sludge was found to be effective for maintaining the stable performance of bioelectrochemical anaerobic digester.

• Journal of Environmental Health Sciences
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• v.28 no.5
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• pp.77-85
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• 2002

The objective of this study was to evaluate the performances of the ASBR under critical conditions of solid-liquid separation, caused by extremely high solids concentration, for wider application of the ASBR to various wastes. The ASBRs and completely-mixed daily-fed control runs were operated using a municipal mixed sludge at 35$^{\circ}C$ and 55$^{\circ}C$. Conversion of completely-mixed daily-fed reactor to sequencing batch mode and changes in HRT of all ASBRs were easily achieved without adverse effect, regardless of digestion temperature. Solids accumulation was remarkable in the ASBRs, and directly affected by settleable solids concentration of the feed sludge. Noticeable difference in solids-liquid separation was that flotation thickening occurred in the mesophilic ASBRs, while gravity thickening was a predominant solid-liquid separation process in the thermophilic ASBRS. Solids profiles at the end of thickening step dramatically changed at solid-liquid interface, and slight difference in solids concentrations was observed within thickened sludge bed. Organics removals based on subnatant or supernatant after thickening always exceeded 80% in all reactors. Thickened sludge volume and gas production of the ASBRs affected mutually. Gas production increased as thickened sludge accumulated, and continuous gas evolution during thickening could cause thickened sludge to expand or resuspend. Thickened sludge volume exceeding a predetermined withdrawal level resulted in loss of organic solids as well as biomass during withdrawal step, leading to decrease in gas production ind SRT. Such an adverse mutual effect was significant in gravity thickening, while it was not sensitive in flotation thickening. Changes in organic loading had no significant effect on organic removals and gas production after build-up of solids in the ASBRs.