Performance and functional flora of simultaneous nitrogen removal, desulfurization and electricity generation in sulfide autotrophic denitrification-anammox-MFC coupled system.

In this study, a novel SAD-anammox-MFC coupled system was constructed for simultaneous nitrogen removal, desulfurization, and electricity generation. The optimal total nitrogen (TN) removal efficiency of 82.1% was achieved under the following conditions: a sludge inoculation ratio (SADB:AnAOB) of 1:2, external resistance of 500 Ω, influent sulfide concentration of 300 mg S/L, and hydraulic retention time (HRT) of 60 h. The maximum power density (1406.25 mW/m3) occurred at 300 mg S/L and an HRT of 24 h. A longer HRT promoted complete sulfide oxidation and allowed anammox to become the dominant nitrogen removal pathway, with the highest coulombic efficiency (18.20%) at 60 h. Microbial community analysis revealed that the cathode was enriched with the anammox bacterium Candidatus Brocadia (35%) and denitrifying bacterium unclassified_f_PHOS-HE36 (5%), while the anode was dominated by Thiobacillus (15%-20%) and Sulfuricurvum (10%-15%), forming a stable functional zonation. This study provides a low-carbon and resource-oriented solution for treating sulfur- and nitrogen-containing wastewater.