Production of C2+products in novel microbial electrosynthesis coupled with anaerobic membrane bioreactor

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 carbon nanotubes based hollow fiber membranes as the separation unit and the biological cathode, simulta-neously. 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%o, 0.75%o, 0.62%o, 0.173%o, 0.19%o, 0.30%o and 0.07%o. 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 (average removal rate of 95.4%). The effluent COD was 0 mg/L for many times during the operation. 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.