A Comparative Research on the Performance of Different Sulfur-Based Autotrophic Denitrification Filter Media in Municipal Wastewater Treatment

Abstract The low carbon-to-nitrogen (C/N) ratio of municipal wastewater treatment plant secondary effluent poses a significant challenge for advanced nitrogen removal. This study developed a novel sulfur–iron–calcium synergistic denitrification filter medium and systematically evaluated its performance under authentic conditions compared to conventional materials. The results demonstrated that the system employing the composite medium (Reactor 2) achieved superior performance, removing 85% of total nitrogen with enhanced stability at a loading of 30 mg/L NO3–-N, significantly outperforming traditional sulfur-based systems. This enhancement was attributed to a pivotal multielement (S–Fe–Ca) synergy: Fe–S cooperation facilitated electron transfer and enriched key genera (e.g., Thiobacillus and Ferritrophicum), while Ca-derived buffering stabilized the system pH. The findings provide a scientifically grounded and practical strategy for energy-efficient upgrading of wastewater treatment plants.