Enhancing bioelectrochemical processes in anaerobic membrane bioreactors for municipal wastewater treatment: A comprehensive review

The coupling of membrane separation technology with anaerobic digestion (AD) treatment in anaerobic membrane bioreactors (AnMBRs) presents a promising approach for municipal wastewater (MWW) treatment, offering exceptional treatment efficiency and the potential to recover valuable bioenergy resources. However, challenges like suboptimal methane production efficiency, refractory substances inhibition, and issues related to membrane fouling pose significant obstacles to the use of AnMBRs in full-scale MWW treatment. In recent years, the combination of AnMBR with bioelectrochemical processes, such as microbial electrolysis cell (MEC), holds great potential to address these challenges, but a systematic analysis is currently lacking. Herein, this study systematically reviewed the enhancement of bioelectrochemical processes in AnMBRs for MWW treatment. We initially identified the primary challenges associated with AnMBR in MWW treatment. On this basis, we described the different integration of MEC with AnMBR (MEC-AnMBR) configurations and highlighted the advantages of MEC-AnMBR technology in treating MWW, including heightened biomass conversion capacity, mitigated substance inhibition and decreased membrane fouling, particularly in low temperature and low organic substrate conditions. The effects of various operating parameters in MEC-AnMBRs treatments, including reactor type, applied voltage, hydraulic retention time (HRT), temperature, and module material were also detailed. Furthermore, we elucidated the mechanisms of the bioelectrochemical processes in MEC-AnMBRs to overcome the limitations of AnMBRs in treating MWW. By accelerating exocellular electron transfer and boosting the activity of electroactive microorganisms (EAMs), the bioelectrochemical processes in AnMBRs are able to improve methane production, eliminate refractory organic matter, and regulate membrane fouling. Finally, this study explored the potential future development of MEC-AnMBRs to enhance material conversion and energy recovery, ultimately promoting a circular economy in the wastewater treatment industry.