Production of C2+ Products in Novel Microbial Electrosynthesis Coupled with Anaerobic Membrane Bioreactor

Abstract

Aim to realize in-situ CO2 reduction to multi-carbon (C2+) products in anaerobic biological treatment systems, a microbial electrosynthesis coupled with anaerobic membrane bioreactor (MES-AnMBR) was constructed with the CNTs based hollow fiber membranes as the separation unit and the biological cathode, simultaneously. Acetic acid and ethanol as the main C2+ products with the highest concentration of 230 mg/L and 7.05 mg/L were obtained in MES-AnMBR, respectively. The genes related to acetic acid and ethanol production were remarkably up-regulated, such as pta, ACSS1_2(acs), ALDH, yiaY, frmA, adhE and yahK with the respective relative abundance of 0.49‰, 0.75‰, 0.62‰, 0.173‰, 0.19‰, 0.30‰ and 0.07‰. Cloacibacterium and Geobacter as types of electrochemically active bacteria could involve in the electron transfer. Macellibacteroides with the abundance of 16.7% became the main bacteria for acetic acid, butyrate and iso-butyrate even ethanol production. Moreover, MES-AnMBR owned a stable and good effluent quality with the average effluent COD of 22.56 mg/L. Benefiting from the electrochemical effect, the main membrane fouling types occurred on the membranes was reversible membrane fouling, which accounted for 52.2% and easily recovered by hydraulic cleaning.

Keywords: Ethanol, membrane fouling, COD, C2+ products, MES-AnMBR