• KSBB Journal
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• v.29 no.4
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• pp.225-231
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• 2014

A microbial fuel cell (MFC) and bioelectrochemical systems are novel bioprocesses which employ exoelectrogenic biofilm on electrode as a biocatalyst for electricity generation and various useful chemical production. Previous reports show that electrogenic biofilms of MFCs are time varying systems and dynamically interactive with the electrically conductive media (carbon paper as terminal electron acceptor). It has been reported that maximum power point tracking (MPPT) method can automatically control load by algorithm so that increase power generation and columbic efficiency. In this study, we developed logic based control strategy for external load resistance by using $LabVIEW^{TM}$ which increases the power production with using flat-plate MFCs and MPPT circuit board. The flat-plate MFCs inoculated with anaerobic digester sludge were stabilized with fixed external resistance from $1000{\Omega}$ to $100{\Omega}$. Automatic load control with MPPT started load from $52{\Omega}$ during 120 hours of operation. MPPT control strategy increased approximately 2.7 times of power production and power density (1.95 mW and $13.02mW/m^3$) compared to the initial values before application of MPPT (0.72 mW and $4.79mW/m^3$).

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.341-345
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• 2009

Continuous dry anaerobic digestion of organic solid wastes (30% TS, Total Solids) comprised of food waste and paper was performed under mesophilic condition. During the operation, hydraulic retention time (HRT) was decreased as follows: 150 d, 100 d, 60 d, and 40 d, which corresponded to the solid loading rate of 2.0, 3.0, 5.0, and 7.5 kg TS/$m^3$/d, respectively. Volumetric biogas production rate ($m^3$/$m^3$/d) increased as HRT decreased, and the highest biogas production rate of 3.49${\pm}$0.31 $m^3$/$m^3$/d was achieved at 40 d of HRT. At this HRT, high volatile solids (VS) reduction of 76% was maintained, and methane production yield of 0.25 $m^3$/kg $TS_{added}$ was achieved, indicating 67.4% conversion of organic solid waste to bioenergy. The highest biogas production yield of 0.52 $m^3$/kg $TS_{added}$ was achieved at 100 d of HRT, but it did not change much with respect to HRT. For the ease feed pumping, some amount of digester sludge was recycled and mixed with fresh feed to decrease the solid content. Recirculation volume of 5Q was found to be the optimal in this experimental condition. Specific methanogenic activity (SMA) of microorganisms at mesophilic-dry condition was 2.66, 1.94, and 1.20 mL $CH_4$/g VS/d using acetate, butyrate, and propionate as a substrate, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.1
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• pp.61-70
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• 2012

Feasibility of co-digestion was investigated by a series of anaerobic batch experiments using sewage sludge, swine waste, and food waste leachate as substrates. The organic solid wastes were collected from M city, where the daily productions of sewage sludge, swine waste, and food waste leachate were 178 ton/d, 150 ton/d, and 8 ton/d, respectively. Both swine waste and food waste leachate showed superior methane yields, methane productivities, and organic pollutant removal efficiencies compared to sewage sludge. Co-digestion of the total amounts of organic solid wastes would enhance methane production by 5.60 times $(530\;m^{3}\;CH_{4}/d\;{\rightarrow}\;2,968\;m^{3}\;CH_{4}/d)$. However, it also increase the amount of digestate by 1.88 times with 3.79 to 4.92 times higher pollutants (chemical oxygen demands total nitrogen, and total phosphorus) loading rates. Co-digestion of organic solid wastes is a valid strategy to enhance the performance of an anaerobic sludge digester and the energy independence of a wastewater treatment plant. Anyhow,the increment of digestate with higher pollutant loading would need a careful counterplan in the operation of the main stream of the treatment plant.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.3
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• pp.35-43
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• 2016

COD properties of waste activated sludge (WAS) were investigated for various solubilization rate of mechanical pretreatment method in anaerobic digestion process. Inert COD was 37.0% of total COD in untreated WAS. Particulate biodegradable COD was converted to soluble biodegradables and particulate unbiodegradables as solubilization was processed. Particulate unbiodegradable portion of COD in WAS can be increased as particulate biodegradable portion is decreased in case of relatively long SRT of biological treatment. Thus, COD properties of WAS should be investigated in case of relatively low particulate biodegradable COD, because of possible low effect of solubilization. COD removal rate in anaerobic digester was enhanced as much as 2.1% and 15.1% for solubilization rate 5% and 35% due to pretreatment, respectively. COD removal rate was increased from 25% to 40%, and methane gas generation was increased from $607m^3/d$ to $907m^3/d$ as particulate COD of WAS was solubilized to 35% in pretreatment facilities.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.3
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• pp.155-161
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• 2012

A simple in-situ methane enrichment system in mesophilic anaerobic digestion was developed to take advantage of the differing solubilities of $CO_2$ and methane. The methane enhancement systems consisted of low solids plug-flow maize digester coupled with a leachate recycle loop to an external $CO_2$ stripper. The effects of leachate recycle rate (LRR) and reactor alkalinity on the resulting offgas $CH_4$ contents, biogas productivity and TVS removal efficiency were quantitively evaluated. The results showed that offgas $CH_4$ contents of over 94% was achieved at 3 volume of leachate recycle per volume of reactor per day (3 v/v-d) and at the reactor alkalinity of 4 g/L as $CaCO_3$, as the optimum operating conditions. The TVS removal efficiency of the methane enhancement system was 79% which corresponds to 94% of the control reactor and the methane productivity appeared to be 0.71 v/v-d. Offgas methane contents correlated well with LRR. However excessively high LRR led to the decrease in TVS removal efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2197-2204
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• 2000

Lignin is a major component of wastewater generated in the chemical processing of wood. Because it is recalcitrant, it inhibits biological treatment of wastewater of pulp manufacturing, especially high concentration of lignin may inhibit the anaerobic digestion. The objective of this study was to evaluate the toxicity of high molecular hardwood lignin (lignosulfonate, MW $\geq$ 20,000) on aceticlastic methanogens in the batch reactors at different temperatures with different sludge concentrations, using anaerobic serum bottles. The hardwood lignin was found to inhibit anaerobic conversion of acetate to methane and carbon dioxide, shown with a long lag-phase before methanogenesis started. The methanogens assumed not to be able to acclimate to the lignin were found to be acclimated slowly in the batch experiments, finally reaching non-toxic levels in which methane production could start. The hardwood lignin was found not to be bacteriocidal but bacteriostatic to aceticlastic methanogens. Hardwood lignin(lignosulfonate) at 1.3, 2.6, and 3.9%(w/w) inhibited the acetateutilizing methanogens of anaerobic digester sludge by 14.5, 17.8, 21.1 days(in noninhibitory condition it took 10 days) to produce the same amount of methane. The inhibitory effect of lignin was examined at temperature ranges of $30^{\circ}C$ to $50^{\circ}C$. When 2.6% of lignin was contained in wastewater, methane production was highest at $30^{\circ}C$ during initial 8 days. At $4^{\circ}C$, methane production rapidly increased after 12 days of digestion, the value became higher than that at $30^{\circ}C$ after 14 days. However, the methane production was completely inhibited during whole digestion period at $50^{\circ}C$. High ratio of lignin concentration to initial anaerobic sludge concentration gave tolerance to the inhibition. In this experiment, high molecular hardwood lignin was not degraded and decolorized.

• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.4
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• pp.67-76
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• 2021

Biogasification is a technology that produces environmentally friendly fuel using methane gas generated in the process of stably decomposing and processing organic waste. Biogasification is the most used method for energy conversion of organic waste with high moisture content, and is a useful method for organic waste treatment following the prohibition of direct landfill (2005) and marine dumping (2013). Due to African Swine Fever (ASF), which recently occurred in Korea, recycling of wet feed is prohibited, and consumers such as dry feed and compost are negatively recognized, making it difficult to treat food waste. Accordingly, biogasification is attracting more attention for the treatment and recycling of food waste. Korea's energy consumption amounted to 268.41 106toe, ranking 9th in the world. However, it is an energy-poor country that depends on foreign imports for about 95.8% of its energy supply. Therefore, in Korea, the Renewable Energy Portfolio Standard (RPS) is being introduced. The domestic RPS system sets the weight of the new and renewable energy certificate (REC, Renewable energy certificate) of waste energy lower than that of other renewable energy. Therefore, an additional incentive system is required for the activation of waste-to-energy. In this study, the operation of an anaerobic digester that treats food waste, food waste Leachate and various organic wastes was confirmed. It was intended to be used as basic data for preparing the waste-to-energy incentive system through precise monitoring for a certain period of time. Four sites that produce biogas from organic waste and use them for power generation and heavy gas were selected as target facilities, and field surveys and sampling were conducted. Basic properties analysis was performed on the influent sample of organic waste and the effluent sample according to the treatment process. As a result of the analysis of the properties, the total solids of the digester influent was an average of 12.11%, and the volatile solids of the total solids were confirmed to be 85.86%. BOD and CODcr removal rates were 60.8% and 64.8%. The volatile fatty acids in the influent averaged 55,716 mg/L. It can be confirmed that most of the volatile fatty acids were decomposed and removed with an average reduction rate of 92.3% after anaerobic digestion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.588-597
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• 2016

In this study, we attempted to improve the biogas production efficiency by varying the mixing ratio of the mixed sludge of organic wastes in the improved single-phase anaerobic digestion process. The types of organic waste used in this study were raw sewage sludge, food wastewater leachate and livestock excretions. The biomethane potential was determined through the BMP test. The results showed that the biomethane potential of the livestock excretions was the highest at $1.55m^3CN4/kgVS$, and that the highest value of the composite sample, containing primary sludge, food waste leachate and livestock excretions at proportions of 50%, 30% and 20% respectively) was $0.43m^3CN4/kgVS$. On the other hand, the optimal mixture ratio of composite sludge in the demonstration plant was 68.5 (raw sludge) : 18.0 (food waste leachate) : 13.5 (livestock excretions), which was a somewhat different result from that obtained in the BMP test. This difference was attributed to the changes in the composite sludge properties and digester operating conditions, such as the retention time. The amount of biogas produced in the single-phase anaerobic digestion process was $2,514m^3/d$ with a methane content of 62.8%. Considering the value of $2,319m^3/d$ of biogas produced as its design capacity, it was considered that this process demonstrated the maximum capacity. Also, through this study, it was shown that, in the case of the anaerobic digestion process, the two-phase digestion process is better in terms of its stable tank operation and high efficiency, whereas the existing single-phase digestion process allows for the improvement of the digestion efficiency and performance.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.4
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• pp.515-523
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• 2012

The study investigated the biochemical methane potential (BMP) assay of cellulose supplementing with mixed methanogens and cellulolytic bacteria to improve anaerobic digestion for methane production. For the BMP assay, 7 different microbial supplementation groups were consisted of the cultures of mixed methanogens (M), Fibrobacter succinogenes (FS), Ruminococcus flavefaciensn (RF), R. albus (RA), RA+FS and M+RA+FS including control. The cultures were added in the batch reactors with the increasing dose levels of 1% (0.5 mL), 3% (1.5 mL) and 5% (2.5 mL). Incubation for the BMP assay was carried out for 40 days at $38^{\circ}C$ and anaerobic digestate obtained from an anaerobic digester with pig slurry as inoculum was used. In results, 5% FS increased total biogas and methane production up to 10.4~22.7% and 17.4~27.5%, respectively, compared to other groups (p<0.05). Total solid (TS) digestion efficiency showed a similar trend to the total biogas and methane productions. Generally the TS digestion efficiency of the FS group was higher than that of other groups showing at the highest value of 64.2% in the 5% FS group. Volatile solid (VS) digestion efficiencies of 68.4 and 71.0% in the 5% FS and the 5% RF were higher than other groups. After incubation, pH values in all treatment groups were over 6.4 indicating that methanogensis was not inhibited during the incubation. In conclusion, the results indicated that the hydrolysis stage for methane production in anaerobic batch reactors was the late-limiting stage compared with the methanogenesis stage, and especially, as the supplementation levels of F. succinogenes supplementation increased, the methane production was increased in the BMP assay compared with other microbial culture addition.

• KSBB Journal
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• v.11 no.2
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• pp.211-217
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• 1996

Batch experiments were conducted to investigate the effect of electron donor on reductive dechlorination of 2,4,5-trichlorophenol by a methanogenic consortium. The methanogenic consortium was obtained from the anaerobic digester of a municipal wastewater treatment plant. The batch reactor containing methanogenic consortium was spiked with 2,4,6-trichlorophenol at 10 mg/$\ell$. Acetate, ethanol, glucose of methanol, each was added as an electron donor for methanogenic consortium. During the course of the experiments liquid samples were taken from the batch reactor to measure dechlorination rate and find the dechlorination pathway of 2,4,6-trichlorophenol. After incubation 2,4,6-trichlorophenol was first dechlorinated to 2,4-dichlorophenol and then to 4-chlorophenol. Phenol was not detected in the batch reactor the highest rate of dechlorination of 2,4,6-trichlorophenol was observed when ethanol was used as an electron donor.