Phosphorus removal performance of Sulfide-Based autotrophic denitrification process

Abstract

Sulfide-based Autotrophic Denitrification (SAD) Process can simultaneous remove sulfurous and nitrogenous pollutants, showing a promising prospect. Beyond our expectation, it also has an efficient phosphorus (P) removal performance. The operation results demonstrated that when the influent concentration of nitrate, sulfide and phosphate was 80.55 ± 2.98 mg N/L, 380.15 ± 20.83 mg S/L and 47.70 ± 4.35 mg P/L respectively, their removal efficiency was 87.63 ± 3.12 %, 99.61 ± 1.02 % and 85.38 ± 4.07 % at the HRT of 8.8 h. However, the phosphorus removal performance disappeared once the effluent pH dropped below 8.0. The random forest regression model revealed that effluent pH had the most significant impact on phosphorus removal performance. This finding was corroborated by a mathematical model that related the phosphate removal load to effluent pHs. The combination of batch test, Standard Measurements and Testing (SMT) and X-Ray Diffraction (XRD) method revealed that the phosphorus removal performance of SAD process came from the synergies of biological phosphorus removal (29.71 ± 3.21 %) and bio-induced phosphate precipitation (70.29 ± 3.21 %). The analysis of key functional genes coding for nitrogen, sulfur and phosphorus metabolism offered an explanation for their metabolic pathways especially the phosphorus removal pathway. The study would provide some new information for the development of SAD process.