15 - Integration of microbial electrolysis cells with anaerobic digestion to treat beer industry wastewater

Abstract

Microbial catalyzed electrochemical systems have been intensively used in basic and applied research as a futuristic and sustainable platform for harnessing the energy and generating value-added bioproducts. Recently, more emphasis is being laid on the enhancement of microbial electrolysis (ME) by inserting anaerobic digestion (AD) into it for the conversion of carbon dioxide directly to methane. This chapter is focused on wastewater treatment experience on the beer industry of Harbin city, China, for methane production in innovative integrated ME-assisted upflow AD (ME–AD) reactors. This chapter focuses on three aspects with a particular emphasis on ME–AD scaling up: (1) suitable cathode electrode material, (2) electrodes position and hydraulic retention times (HRTs), and (3) cathode/anode ratio (cathode surface area/anode spatial volume). The combined reactors were thus enabled to achieve maximum organic content removal, enhanced current generation, and heightened methane production, by implementing these upgrading techniques. Ni cathode electrodes were identified to be the most appropriate for employment in the ME–AD reactors. The reactors with electrodes arranged at the bottom side were better in performance at 36h HRT. The effects of electrode placement on biofilm microbial communities (electrogens and methanogens) were estimated by pyrosequencing methods. A cathode/anode ratio of 2.5cm2/cm3 was determined to have improved our combined reactor performance. Thus these unique reactors were application-oriented, membrane-free, continuous reactor with shortened reaction time, enhanced electrode ration for improving the bioelectricity generation, and organic content oxidation to methane.