Electrochemical regulation creates dual carbon-mitigation pathways in an anaerobic electrochemical membrane...

Achieving low-carbon goals in urban membrane-based biological wastewater treatment requires both enhanced energy recovery and reductions in the hidden carbon costs associated with membrane fouling control. Here, an anaerobic electrochemical membrane bioreactor (AnEMBR) was employed as a model platform to examine how electrochemical regulation can create dual carbon-mitigation pathways through improved methane recovery and reduced fouling burden. At 1.0 V, the AnEMBR achieved 98.9% COD removal and a 33.3% increase in methane yield (159.0 ± 1.6 mL CH₄/g-COD_re) over the control. This enhancement was associated with electrochemically differentiated microbial niches, fostering dense electroactive biofilms and selectively enriching hydrolytic, acidogenic, and methylotrophic functional populations on the anode, while favoring hydrogenotrophic methanogens on the cathode. Simultaneously, electrical regulation modulated biomass filtration performance, reducing the membrane fouling rate to 0.35-0.13 kPa/d across the three operational stages, corresponding to reductions of 46.6%-76.0% relative to the conventional benchmark. Micro-CT analysis revealed an electro-modulated micro-channel mechanism, where the bio-cake transformed into a porous, interconnected matrix that likely facilitates water channeling and reduces filtration resistance. Consequently, synergistic methane recovery and mitigation of hidden carbon costs from fouling control enabled the AnEMBR to achieve a net-negative operational carbon footprint of -0.11 kg CO₂eq/m³. These findings provide mechanistic evidence that electrochemical regulation can reduce the operational carbon footprint of anaerobic wastewater treatment through coupled bioenergy-recovery and fouling-control pathways.