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Methane Recovery from NaCl Inhibition of Food Waste Anaerobic Digestion
( Jae Hac Ko ),( Danling Xia ),( Qiyong Xu ) 한국폐기물자원순환학회(구 한국폐기물학회) 2020 한국폐기물자원순환학회 추계학술발표논문집 Vol.2020 No.-
One of the big challenges of food waste anaerobic digestion is the inhibition of high NaCl concentrations. This study investigated the effects of NaCl fluctuation on the methane generation of food waste anaerobic digestion under both thermophilic and mesophilic conditions, especially focusing on shock loading of high NaCl concentration with/without water dilution treatment. In general, methane generation decreased with increasing the concentration of NaCl concentrations. Thermophilic AD was more sensitive to NaCl concentration change at the range of 5-10 g/L. When NaCl concentration increased from 0 g/L to 30 g/L, the accumulative methane volumes of thermophilic and mesophilic reactors decreased from 420 mL to 133 mL and from 529 mL to 133 mL, respectively. With increasing NaCl concentration, pH of digestate decreased while COD and VFA concentrations increased. Results indicated that a shock-loading of NaCl significantly reduced methane generation. Using water dilution as a remedial measure, the methane generation rates could be recovered up to 64% - 72%. Further investigation with 16S rRNA analysis showed that the predominant genus of methanogens shifted from Methanoculleus to Methanosarcina after removal of osmotic stress by water dilution.
Municipal Solid Waste Degradation and Compaction
( Jae Hac Ko ),( Mingying Li ),( Fan Yang ),( Qiyong Xu ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-
This study investigated the impact of compaction on anaerobic degradation of municipal solid waste (MSW) during the phase of methane formation. Two stainless steel lysimeters were constructed with equipped a hydraulic cylinder to apply pressure load on the MSW. When methane production rates decreased from the peak rate of each column, pressure load was applied at different degrees of decomposition (DOD). When pressure load was applied, chemical oxygen demand (COD) showed temporary increases, Methane production rate also increased by the compaction. However, the impact of compaction on methane production rate varied with different degrees of decomposition. MSW compaction reduced pore space of MSW resulting in increasing the contact surface area of among MSW particles. It was thought that the mass transfer of volatile fatty acids could be enhanced by increased contact surface area and degree of saturation as the consequence of the compaction.
Biogas Recovery from MSW using Different Aeration Pretreatments
( Xu Qiyong ),( Tian Ying ),( Ko Jae Hac ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-
Aeration pretreatment has been proven to be an efficient technology to facilitate waste stabilization in bioreactor landfills. In order to investigate the effects of different aeration pretreatments on biogas recovery, three simulated columns (A1, C1 and C2) were constructed and operated for 130 days. A1 simulated an anaerobic bioreactor. C1 was pretreated with a constant daily aeration frequency in the upper layer, while C2 had various daily aeration frequencies. Results indicated that aeration could effectively remove high volatile fatty acid (VFA) in leachate and accelerate methane productions in bioreactors. At the end of operation, about 44 L/kgdry mass and 53 L/kgdry mass methane were collected in C1 and C2, respectively, while nearly no methane was produced in A1. Correspondingly, aerobically pretreated bioreactors dramatically decreased their COD and VFA concentrations. In terms of methane formation in aerobically pretreated bioreactors, C2 was changed quickly from aerobic phase to methanogenic phase. Due to larger area affected by aeration pretreatment, biogases in C1 were generated in much greater rate. The total amount of methane generated from C2 was greater than that from C1.
Impact of Additional Downward Gas Collection on MSW Landfill Performance
( Iyong Xu ),( Jie Qin ),( Jae Hac Ko ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
A municipal solid waste landfill still has played an important role as a solid waste management option. This study investigated the performance of simulated landfills with different biogas collection practices, including upward biogas collection only (LT) and both upward and downward biogas collection (LTB). In addition, the effects of leachate recirculation on the landfill performances were examined with the different gas collection practices. A stainless steel lysimeter equipped with a compression unit was used to simulate a landfill. With reducing void ratio in LT, high pressure buildup was observed and porched leachate was formed because of high resistance of upward gas flow against downward leachate flow. When both upward and downward gas flows were allowed (LTB), upward gas flow was favored in uncompressed MSW. During reducing void ratio from 2.5 to 1.0, the preferential flow direction of biogas was changed to downward gas flow along with gravimetric leachate drainage in LTB. It was considered that pressure buildup in LT gas-filled pores inhibited methane production by enhancing uneven moisture distribution. The effect of leachate recirculation in LT also was minor compared to that of LTB. Starting downward gas collection in LT, the porched leachate was disappeared. However, the performance of LT was not improved considerably after starting the downward gas collection. The cumulative methane volume produced from LTB was 1.5 times as much as that of LT. Enzyme activity analysis indicated that the enzyme activities of LTB were higher than those of LT due to increasing even moisture distribution and contact opportunity with organic matter. The results of microbial community analysis also showed that different LFG collection practice could affect microbial diversity.
( Eunil Cho ),( Qiyong Xu ),( Danling Xia ),( Jae Hac Ko ) 한국폐기물자원순환학회 2021 한국폐기물자원순환학회지 Vol.38 No.4
One of the significant challenges of food waste anaerobic digestion (AD) is the negative effect of high NaCl concentrations. This study investigated the effects of NaCl fluctuation on the methane generation of food waste AD under thermophilic and mesophilic conditions. Particularly, the effects of the shock loading of high NaCl concentration with/ without water dilution treatment were investigated. Generally, the methane generation decreased with increasing NaCl concentration. In addition, the sensitivity of the thermophilic AD to NaCl concentrations (5-10 g/L) was higher than that of the mesophilic AD. Furthermore, with an increase in the NaCl concentration from 0 to 30 g/L, the accumulative methane volumes of the thermophilic reactors decreased from 210 to 45 mL/gVS, and those of the mesophilic reactors decreased from 265 to 67 mL/gVS. Additionally, the pH of digestate decreased with increasing NaCl concentration. In contrast, the concentrations of the chemical oxygen demand and volatile fatty acid increased with increasing NaCl concentration. These results indicated that a shock loading of NaCl significantly reduced methane generation. In addition, the methane generation rates could be recovered up to 64-72% using water dilution as a remedial measure. Further investigation using 16S rRNA analysis revealed that the predominant genus of the methanogens shifted from Methanoculleus to Methanosarcina after the removal of the osmotic stress using water dilution.