結合生物電化學和厭氧消化：施加定電位對系統的影響評估

Abstract

厭氧消化在執行污泥減量的處理時，能同時以甲烷的形式回收污泥的能量，但礙於反應熱力學與動力學的限制，處理效率還有待進一步提升。而生物電化學系統則是利用生物電極處理生物廢物及產能。本研究主旨在於利用輔助生物電化學系統結合厭氧消化，藉由施加恆定工作電位(-0.7 V、-0.3 V、0.1 V vs. SHE和開路控制)，以期望增進厭氧工藝減廢及能量回收的效率。 本實驗採集八里污水廠之污泥，在設置含有三電極體系的無膜消化槽執行30天的產氣潛能試驗，運行過程持續監測電化學活性及有機物變化。其結果顯示，施加電位0.1 V組回饋了極高的正電流，與之同時引起電極表面之生物聚積，而由循環伏安法也測得最高電流密度之氧化峰。污泥減量上，VS去除率以0.1 V最高，並相較於其他條件，0.1 V組的反應遲滯期最為短暫，13天內即可達50%的TCOD去除率，最大日產甲烷速率比控制組增加了9.1%，並且是唯一產氫的可行條件，與之同時，0.1 V也成功抑制了硫化氫的生產。相對下，-0.7 V組則產生負電流，同時會增加酸化作用，提升揮發性脂肪酸的總體水平。最後-0.3 V組在系統表現上，顯示與控制組相同的反應特徵及趨勢。 四種電位條件的菌群結構，以相對豐度約5%以上之水解菌和60%以上之產酸菌/產乙酸菌所組成。在古菌方面，0.1 V組以氫營養型產甲烷菌Methanobacterium為優勢屬，-0.7 V、-0.3 V和控制組則以乙酸營養型產甲烷菌Methanosaeta為優勢，並且隨著系統產生的電流增加，氫營養型產甲烷菌於系統的相對豐度也隨之增加。而在電極的菌群上，Geobacter之相對豐度也隨著電位提升至陽極電位而增加。 而不同有機負荷下，生物電化學系統運用於單室消化槽的影響成效會因污泥有機固體濃度增加而降低，但仍然會影響沼氣產物的組成。

Anaerobic digestion can reduce sludge. At the same time, the energy of the sludge is recovered in the form of methane. However, the processing efficiency needs to be improved due to reaction thermodynamics and kinetics limitations. Bioelectrochemical systems are technologies that use electrodes to treat biological waste and generate energy. This study aims to couple anaerobic digestion with a bioelectrochemical system, hoping to increase the waste reduction and energy recovery of the anaerobic process by applying constant working potentials (-0.7 V, -0.3 V, 0.1 V vs. SHE and open-circuit control). In this experiment, the sludge from Bali Sewage Treatment Plant was collected. Biochemical methane potential test ran for 30 days in a membraneless reactor with a three-electrode system. The electrochemical activity and changes in the organic matter were continuously monitored during the operation. The results showed that the applied potential of 0.1 V gave back a very high positive current. At the same time, organisms accumulated on the electrode surface. The oxidation peak with the highest current density was also measured at 0.1 V by cyclic voltammetry. In terms of sludge reduction, the 0.1 V has the highest VS removal rate. Compared with other conditions, the 0.1 V has the shortest lag period and can reach 50% TCOD removal rate within 13 days. The maximum methane production rate per day increased by 9.1% over the control and was the only feasible condition for hydrogen production. The inhibition of hydrogen sulfide generation was also successfully achieved at 0.1 V potential. In contrast, the -0.7 V produced a negative current, and the overall level of volatile fatty acids also increased. Finally, the -0.3 V showed the same reaction characteristics and trend as the control in terms of system performance. The microbial community of the four potential conditions is composed of hydrolytic bacteria with a relative abundance of more than 5% and acidogenic bacteria /acetogenic bacteria with a relative abundance of more than 60%. Among the archaea, 0.1 V was dominated by the hydrogenotrophic methanogens Methanobacterium, and -0.7 V, -0.3 V, and control were dominated by the acetoclastic methanogens Methanosaeta. As the current generated by the system increased, the relative abundance of hydrogenotrophic methanogens in the system also increased. As for the microbial structure of the working electrode, the relative abundance of Geobacter also increased with increasing potential. In terms of different organic loads, the effect of bioelectrochemical systems used in the single-chamber digester was reduced due to the increase in the concentration of organic solids in the sludge. However, it still affects the composition of biogas.