Low-biofouling anaerobic electro-conductive membrane bioreactor: The role of pH changes in bacterial inactivation and biofouling mitigation

Membrane biofouling presents a great challenge to the adoption of anaerobic membrane bioreactors (AnMBRs) for wastewater treatment. A promising method for mitigating biofouling is applying an external charge to carbon-based electroconductive membranes (ECMs). This research investigated biofouling mitigation in an AnMBR mimicking system equipped with an ECM (EC-AnMBR), where the ECM serves as a cathode and a platinum plate as the counter electrode. A cation exchange membrane separated the anode and cathode to decouple the reactions on each electrode. Bacterial inactivation was estimated under varying cathodic potentials (0 to −2.5 V vs. Ag/AgCl), and reactive oxygen species formation and changes in pH were monitored. Bacterial inactivation was also evaluated in solutions with pH values similar to those recorded in the applied potentials experiments. Biofouling formation under the different applied potentials was then assessed during 48 h of filtration, and the biofilm formed on the ECM after 48 h was analyzed. Our results show that the EC-AnMBR had very low biofouling, attributed to bacterial inactivation and biofilm mitigation from extreme local pH conditions developed by hydrogen evolution at the cathode. This work addresses biofouling mechanisms on externally charged ECMs, which could be potentially applicable to AnMBRs for advanced wastewater treatment.