The Application of Sn2− 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 (Sn2−). 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 NO3−-N, corresponding to a removal efficiency of 23.1%. No significant accumulation of NO2−-N 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.