Electrically conductive membrane-based anammox MBR with electrochemical assistance: an effective strategy for simultaneous mitigation of membrane fouling and enhancement of nitrogen removal

Anammox is an energy-efficient and low-carbon nitrogen removal process. However, its implementation is hindered by the challenges of effectively enriching anammox bacteria (AnAOB) biomass and maintaining sustained bioactivity. Anammox membrane bioreactor (Amx-MBR) can intercept AnAOB efficiently, but it faces the challenge of membrane fouling. In this study, a novel electrically conductive membrane-based anammox membrane bioreactor with electrochemical assistance (Amx-EMBR) was proposed to mitigate membrane fouling and simultaneously promote AnAOB enrichment and bioactivity. The nanocarbon-based electrically conductive membranes served as the cathode and the carbon fiber brushes with high conductivity and surface areas served as the anode. Over a 72-day operational period, the Amx-EMBR exhibited significant improvements in mitigating membrane fouling, enriching AnAOB populations, and enhancing nitrogen removal performance. The utilization of electrically conductive membranes as cathode resulted in electrostatic repulsion between extracellular polymeric substances and membrane, thereby mitigating membrane fouling significantly. Furthermore, employing carbon brushes as the anode materials facilitated Candidatus Jettenia and Candidatus Kuenenia enrichment, enhanced key enzymes activities, as well as upregulated the genes expression related to anammox, thereby enriching anammox metabolic pathway. Moreover, the external potential induced the upregulation of key genes expressions participated in extracellular electron transfer process, as well as facilitated electron transfer and storage capacity, thereby accelerating the potential extracellular electron transfer of AnAOB. This study presents an effective strategy for mitigating membrane fouling and enhancing anammox performance simultaneously, demonstrating its potential for energy-efficient and low-carbon nitrogen removal in the wastewater treatment.