Response of ammonium transformation in bioanodes to potential regulation: Performance, electromicrobiome and implications

Understanding how potential regulation affects ammonium transformation in bioanodes is crucial for enhancing their application potential. This study systematically explored the operational performance, electrochemical properties, microbial communities, and functional genes of bioanodes across potentials from 0.0 V to 0.4 V vs. SHE. The results indicate that higher anode potentials enhanced electro-biofilm activity and ammonium removal but suppressed nitrite oxidation while favoring dissimilatory nitrate reduction (DNRA), leading to increased nitrite accumulation. This was accompanied by a reduction in nitrite-oxidizing bacteria (NOB) and an increase in DNRA-related genes, resulting in an optimal nitrite-to-ammonium ratio of 1.32 for the Anammox process. Conversely, lower anode potentials improved total nitrogen removal by enhancing nitrite oxidation and denitrification, with increased NOB abundance and denitrification genes accelerating the process. These findings demonstrate that anode potential regulation can steer ammonium transformation in bioanodes toward either N2 production via ammonium oxidation-denitrification or nitrite provision for Anammox.