Unlocking microbial community succession and key influencing factors during bioelectrocatalytically-driven simultaneous removal of ammonia nitrogen and sulfate from wastewater

Ammonia nitrogen (NH₄⁺-N) and sulfate (SO₄²⁻) removal by Anaerobic ammonium oxidation (Anammox) and sulfate-reducing bacteria (SRB) was studied in dual-chamber microbial electrolysis cells (MECs). Appropriate anode potential stimulation promoted biofilm formation and enhanced extracellular polymeric substances fluorescence, facilitating electron transfer. The highest NH₄⁺-N removal (81.1 %) was achieved at the anode potential of 0.6 V vs. Ag/AgCl after 50 days, coinciding with the increase in electroactive Candidatus_Brocadia from 1.1 % to 27.4 %. Simultaneously, SO₄²⁻ removal reached 77.0 %, supported by cathodic biofilms dominated by SRB (Desulfofustis, Desulfomicrobium, and Desulfatirhabdium). Automated machine learning and principal co-ordinates analysis identified the anode potential as the key factor shaping microbial ecology. The appropriate anode potential (0.4–0.6 V vs. Ag/AgCl) promoted cathodic sulfidogenesis, indirectly enhancing electron flow and supporting Anammox process at the anode. These findings demonstrate that MECs hold great promise for simultaneously enhancing anaerobic ammonia oxidation bacteria and SRB activities, enabling efficient NH₄⁺-N and SO₄²⁻ removal.