The Application of S_n²⁻  in Autotrophic Denitrification Process for Advanced Nitrogen Removal in Wastewater Treatment

This study presents a cost-effective and feasible technique for the deep denitrification of wastewater, based on sulfur autotrophic denitrification mediated by polysulfides ((Formula presented.)). Various polysulfides were used as electron donors in an aerobic/anoxic sequencing batch reactor (SBR) to simulate nitrification and denitrification processes. The performance of different polysulfide species and their respective dosages were evaluated to determine the optimal conditions for nitrogen removal. Under optimal nitrogen removal conditions with a dosing of 19.2 mg S/L from Na₂S₃, the system was operated continuously for 38 days, with low sludge production during the process. During stable operation, the system achieved an average removal of 7.3 mg/L of (Formula presented.), corresponding to a removal efficiency of 23.1%. No significant accumulation of (Formula presented.) was observed in the effluent, and the average utilization efficiency of Na₂S₃ reached 83.7%. Continuous dosing of Na₂S₃ promoted the enrichment of sulfur autotrophic denitrification-related microorganisms within the system.