• Journal of Environmental Health Sciences
• /
• v.32 no.2 s.89
• /
• pp.179-185
• /
• 2006

Effect of organic loading rate on UASB performance was evaluated under the renditions of some surface area/reactor volume ratio and different reactor diameter. At the low leading rate of 0.4 kg $COD/m^3{\cdot}d$, reactor performance was not affected by reactor diameter. At the organic loading rate of 6 kg $COD/m^3{\cdot}d$, however, volatile acid accumulation and low COD removal efficiency is observed in reactor having 6.4 cm diameter, while volatile acid is not accumulated at all and high COD removal efficiency is observed in reactor having 3 cm diameter. Such a difference of reactor performance depending on reactor diameter can be explained that sludge bed can be fluidized by evolved gas bubble in narrow reactor, while sludge bed ran not be fluidized by evolved gas bubble only in wide reactor. At a high organic loading rate of 20 kg $COD/m^3{\cdot}d$, it can be judged that there is no relation between reactor configuration and reactor performance because all reactors showed very low COD removal efficiencies regardless of reactor diameter. Narrow and tall type reactor is favorable condition for making sludge bed fluidization at a constant surface area/reactor volume ratio. Thus, it can be judged that reactor configuration and sludge bed fluidization have great influence to reactor performance.

• Journal of Korean Society on Water Environment
• /
• v.20 no.5
• /
• pp.480-487
• /
• 2004

This study was conducted to find the effect of electron acceptors on the formation of granular sludge by using four different types of electron acceptors. The phosphorous uptake, denitrification, and sulfate reduction in anoxic modes were simultaneously occured because of the presence of the polyphosphate accumultating organism(PAO) that utilize nitrate and sulfate as an electron acceptor in the anoxic zone. Denitrirying phosphorous removal bacteria(DPB) was enriched under anaerobic/anoxic/aerobic condition with a nitrate as an electron acceptor, and desulfating phosphorous removal bacteria(DSPB) was enriched under anaerobic/anoxic/aerobic condition with a sulfate as an electron acceptor. Polyphosphate accumulating organism(PAO) were enriched in the anaerobic/aerobic SBR. PAO took up acetate faster than DPB and DSPB during the aerobic phase. The sludge with nitrate and sulfate as an electron acceptors grew as a granules which possessed high activity and good settleability. In the anaerobic/aerobic modes, typical floccular growth was observed. In the result of bench-scale experiment, simultaneous reactions of phosphorus uptake, denitrification and sulfate reduction were observed under anoxic condition with nitrate and sulfate as an electron acceptors. These results demonstrated that the anaerobic/anoxic modes with nitrate and sulfate as an electron acceptors played an important role in the formation of the sludge granulation.

• Journal of Korean Society on Water Environment
• /
• v.31 no.6
• /
• pp.599-609
• /
• 2015

In order to investigate why OSA (oxic-settling-anaerobic) process produces less sludge than CAS (conventional activated sludge) process, sequential cultivation through 1^st aerobic-anaerobic-2^nd aerobic conditions, were carried out. Then, the intracellular concentrations of adenosine triphosphate (ATP), nicotinamide adenine dinucleotide (NAD and NADH), and nicotinamide adenine dinucleotide phosphate (NADP and NADPH) were monitored for these three stages. Results showed that the concentrations of these energy substances rapidly decreased through time in both aerobic and anaerobic conditions but the anaerobic culture contained the lower energy level than aerobic culture. The 2^nd aerobic culture that experienced anaerobic condition showed lower concentration of these energy substances than those of the 1^st aerobic culture. Meanwhile, the anaerobic culture corresponding to the sludge holding stage of OSA was subjected to different soluble chemical oxygen demand (SCOD) levels, detention time, and temperature to evaluate the effects of these variations on the energy level difference between the 1^st and 2^nd aerobic stages. The lower the SCOD concentration, the longer detention time; and the higher temperature in the anaerobic stage tended to further reduce the intracellular level of the 2^nd aerobic culture. On the average, the intracellular energy level of the anaerobic and 2^nd aerobic stage were 57.73% and 39.12% of the 1st aerobic culture, respectively. These indicated that the insertion of an anaerobic stage between two aerobic stages could lower the intracellular energy levels, hence the lower the sludge in OSA than CAS process. Moreover, manipulation of the operating conditions of the intervening anaerobic stage can change intracellular energy levels thereby controlling sludge production.

• Journal of Environmental Science International
• /
• v.1 no.2
• /
• pp.125-136
• /
• 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 the Korea Organic Resources Recycling Association
• /
• v.7 no.2
• /
• pp.47-55
• /
• 1999

Recently, the treatment of that wastes according to increase of food waste has been a great problem of modern society for long time. This study was aimed to evaluate possibility for food waste and sewage sludge mixture treatment using pilot scale two-phase anaerobic digester. Pilot scale two-phase anaerobic digestion system was performanced at 1 : 9 mixture ratio of food waste and sewage sludge infield. The detention time of digester was 20days. The average COD and VS removal efficiencies in organic loading rate $3.03kg\;TCOD/m^3-day$ were 57.7 and 47.7%, and the gas production rate and methane content were $0.4m^3/kg$ VS-day and 65.3%, respectively. TS, VS and VS/TS(%) of mixing tank were 4.44%, 2.59% and 58.34%, respectively and TS. VS and VS/TS(%) of digester in steady state were 3.32%, 1.39% and 41.90%, respectively, Through this study. it was possible to accomplish effective mixture treatment of the sewage sludge and food waste.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.26 no.3
• /
• pp.47-54
• /
• 2018

This study examined the improvement of anaerobic digestion rate and sludge reduction as a result of the addition of anaerobic digestion with thickened sludge and solution of VFAs obtained from food waste. The methane production rate of the digestion system was 2.21 times higher when anaerobic digestion reactor injected into anaerobes with VFAs from food wastes of 5 percent. Also, The reduction of the amount of concentrated sludge injected will proceed rapidly because of the TCOD concentration in the digestion reactor was more than twice higher. Indirectly it was shown that the increased production system contributed significantly to the methane production efficiency.

• Korean Journal of Environmental Agriculture
• /
• v.25 no.3
• /
• pp.247-256
• /
• 2006

This study has been conducted for the process of food wastes disposal using surplus capacity of established sewage treatment plant by co-digestion of fermented food wastes and sewage sludge after thermophilic acid fermentation of food wastes. The co-digestion of thermophilic acid fermented food wastes and sewage sludge was performed by semi-continous method in mesophilic anaerobic digestion reactor. It showed great digestion efficiency as the average SCOD and VS removal efficiency in organic loading rate 3.30g VS/L.d. were 74.2% and 73.6%, and the gas production rate and average methane content were 0.440 L/g $VS_{add}.d$ and 66.5%, respectively. Based on the results of this study, the co-digestion of thermophilic acid fermented food wastes and sewage sludge in sewage treatment plant is able to improve treatment efficiency of anaerobic digestion reactor and to dispose food wastes simultaneously, and was proved excellent economical efficiency comparing with any other treatment methods.

• Membrane and Water Treatment
• /
• v.10 no.3
• /
• pp.213-221
• /
• 2019

Anaerobic digestion (AD) has been widely used to valorize food waste (FW) because of its ability to convert organic carbon into $CH_4$ and $CO_2$. Korean FW has a high content of fruits and vegetables, and efficient hydrolysis of less biodegradable fibers is critical for its complete stabilization by AD. This study examined the digestates from different anaerobic digesters, namely Rs, Rr, and Rm, as the inocula for the AD of vegetable waste (VW) and cellulose (CL): Rs inoculated with anaerobic sludge from an AD plant, Rr inoculated with rumen fluid, and Rm inoculated with anaerobic sludge and augmented with rumen fluid. A total of six conditions ($3\;inocula{\times}2\;substrates$) were tested in serial subcultures. Biogas yield was higher in the runs inoculated with Rm than in the other runs for both VW (up to 1.10 L/g VS added) and CL (up to 1.05 L/g VS added), and so was biogas production rate. The inocula had different microbial community structures, and both substrate type and inoculum source had a significant effect on the formation and development of microbial community structures in the subcultures. The overall results suggest that the bioaugmentation with rumen microbial consortium has good potential to enhance the anaerobic biodegradability of VW, and thereby can help more efficiently digest high fiber-content Korean FW.

• Journal of Environmental Health Sciences
• /
• v.23 no.1
• /
• pp.28-33
• /
• 1997

This study was carried out to investigate factors affecting anaerobic digestion enhancement of waste activated sludge(WAS). In order to this investigation, the degradability and rupture of microorganisms cell present in WAS, and mesophilic anaerobic digestion(MAD) of these compounds, were also evaluated. The micro-organisms cell in WAS were ruptured by a mechanical jet stream and smashed under pressure of 30 bar. The rupture level of micro-organisms cell in WAS were determined using phosphate, soluble protein and soluble chemical oxygen demand (SCOD)concentrations. It was found that the rupture level of micro- organisms cell within WAS increased with increasing pretreatment times, and the pretreated WAS once under pressure of 30 bar resulted in an increase in VS removal and methane production of 5%, 9% over the intact WAS of 35%, 71%, respectively, in batchwise MAD of 6-day and 14-day retention time. With the pretreatment and MAD of 6-day retention time used, mesophlic bioconvertibility as the biogasification of WAS were found to be significantly higher biogas of 1, 850 ml than 300 ml under intact WAS. In conclusion it can be stated mechanical pretreatment enhances WAS bioconvertibility, while under identical treatment conditions, resulted in a considerable decrease in the bioconvertibility of intact WAS.

• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.417-420
• /
• 2008

Recently, the interest in NDMA(N-nitrosodimethylamine) has increased due to its recognition as a pollutant by Ontario Ministry of Environment and Energy and California Department of Health Sciences. It is, in fact, one of the DBPs(Disinfection By-products) which appears due to chlorination and is reported to be fatal if exposed continuously to human body. Due to uncertainty in mechanism to remove it, its treatment is not yet carried out. In this experiment, treatment of biological NDMA is carried out by letting it adsorbed on Granular Sludge and then filtering the medium through MF(Microfiltration) and UF(Ultrafiltration) membranes. Granular Sludge is adapted to aerobic and anaerobic conditions for 7 days and the experimental conditions are MLSS of 8000mg/L, COD of 250mg/L, TN of 12.5mg/L, and TP of 2.5mg/L. Several batch tests were carried out and samples were collected with the interval of 1 hour. Samples were measured by LSC(Liquid scintillation counter) after filtering by MF and UF. In batch test with granular sludge the permeate concentrations(removal efficiencies) of NDMA by MF and UF were 71.7ng/L(32.0%) and 62.0ng/L(43.7%) at aerobic state, and 52.0ng/L(49.2%) and 47.6ng/L(58.9%) at anaerobic state, respectively. Hence, UF membrane showed about 10% more removal efficiency than MF and removal efficiency at anaerobic condition was 15% more than that at aerobic condition.