생물전기화학 혐기성 소화조의 성능에 대한 전극충진율과 다전압인가법의 영향

Abstract

Bioelectrochemical anaerobic digestion is an advanced technology for stabilizing organic wastes, as well as generating methane gas as a by-product. In bioelectrochemical anaerobic digester, electron, proton and carbon dioxide can be produced from organic matter on anode. Cathode use electron and carbon dioxide for producing methane gas. Currently, there are many researches trying to develop bioelectrochemical technology. But it needs more researches to improve the performance of bioelectrochemical anaerobic digestion. In this research, two types of digesters were operated for electrode packing ratio(EPR) and multi-voltage application. One of the digesters had total 7.2m2/m3 of electrode packing ratio which was gradually reduced from 7.2m2/m3 to 0m2/m3 in 3 stages. Other digester had 6sets of separator and electrode assembly(SEA) and was applied multi-voltage(0.3V, 0.5V, 0.7V) to each SEA according to single, dual and tri voltage. As a result, Reduced electrode packing ratio affected performance of bioelectrochemical anaerobic digester directly. At 7.2m2/m3, specific methane production and methane composition were 561.9mL CH₄/L.d and 69.4%. At 3.6m2/m3, specific methane production and methane composition were 408.2mL CH₄/L.d and 68.1%, but operation of control cannot be maintained by short HRT(10days). State variables in research were stable except for control. At the end of control operation, pH was 6.6. According to reduced EPR, performance of bioelectrochemical was decreased. However, Energy efficiency was 65.3% at 3.6m2/m3 which is the highest value. In this research, we found that performance of bioelectrochemical anaerobic digester is related to bacteria like as deltaproteobacter, which controls direct interspecies electron transfer(DIET) for methane reduction. Deltaproteobacteria was 1.64% at 7.2m2/m3 . It was higher 15-25% than 3.6m2/m3 and control.

Multi-voltage application influence the performance rate in a unstable manner. Bioelectrochemical anaerobic digester shows high performance when applied to single voltage which had 654.0mL CH₄/L.d of specific methane production and 71.6% of methane composition. Alkalinity and VFAs concentration were 3,946.6 mg/L as CaCO₃and 746.0mg COD/L. When applied to dual voltage(0.3V, 0.5V), specific methane production and methane composition were decreased to 367.3mL CH₄/L.d, 67.8%. But when applied to tri-voltage, methane composition was increased to 71.3%. This indicates that tri-voltage have more methane reduction reaction than dual-voltage application because of electric potential of 0.7V. When applied to 0.7V, electric potential had proper range from -0.580V to +0.120V(vs. Ag/AgCl) for oxidization and methane reduction on electrode. Multi-voltage application have poor performance but have a possibility for having higher performance when maintained in a proper electric potential.