Electron-acceptor-driven redox reconfiguration enables nitrogen polishing in a bioelectrochemical reactor operated in sequential batch mode

within 10-12 h. Biomass stabilised at approximately 3,000-3,500 mg/L after initial reduction, indicating microbial adaptation. Microbial and functional analyses suggested multiple coexisting pathways, including nitrite-associated processes, dissimilatory nitrate reduction to ammonium, and sulfur-linked reactions. Overall, nitrogen conversion was governed by dynamic redox reconfiguration driven by electron-acceptor availability, rather than a single dominant pathway, highlighting its potential as an energy-efficient nitrogen polishing strategy.