Mechanism and effect insight on stabilizing biological S0 in sulfur-rich wastewater

To improve the recovery rate of biological elemental sulfur(S0) in the simultaneous denitrification and sulfur removal process in sulfur wastewater, the effect and mechanism of stabilizing biological S0 in sulfur-rich wastewater were studied. The experiments were conducted using blockers to stable biological S0 in sulfur-rich wastewater(300 mg/L S2-) and sulfur-poor wastewater(200, 100 mg/L S2- ). It was found that in sulfur-rich wastewater, 68.79 mg/L of S0 was accumulated in the stable group (adding 30 mg/L blocker) at 60 h, which was 25.34 mg/L higher than that in the unstable group (adding 0 mg/L blocker), the S0 stability rate reached 58.31% and the S0 recovery rate was 36.84%. However, the S0 in sulfur-poor wastewater (200, 100 mg/L S2-) was unstable, the S0 stability rate was only 11.2%, 14.14%, and the S0 recovery rate was low (15.71%, 12.39%). It could be seen that the blockers stabilized the biological S0 in sulfur-rich wastewater. Additionally, the blockers were conducive to the accumulation of denitrifying bacteria and Thiobacillus denitrificans, and the high proportion of Thiobacillus denitrificans was conducive to stable S0 in sulfur-rich wastewater. The blockers inhibited the formation of thiosulfate and sulfate and made nitrate get more electrons(19.76 mmol/L more electrons in stable group than in unstable group), promoting the generation and stability of biological S0. This technology could provide a theoretical basis for the recovery and utilization of biological S0 in wastewater.