A novel phosphorus removal process in the sulfide-based autotrophic denitrification system

The conventional biological nitrogen and phosphorus removal often faces the challenge of insufficient organic matter. The sulfide-based autotrophic denitrification (SAD) can remove nitrogenous pollutants without organic matter. Excitingly, SAD can also remove phosphorus, which caters to the principles of carbon neutrality and energy efficiency. The long-term operation of SAD system demonstrated that the phosphorus removal efficiency was 85.9 ± 4.5 %, maintaining the good nitrate and sulfide removal performance of 88.1 ± 8.4 % (N) and 98.6 ± 3.4 % (S), respectively. The batch experiment proved that the phosphorus removal mainly resulted from the bio-induced chemical precipitation, in which alkaline condition (pH>7.5) and sufficient bio-S0 (>25 mg/L) were two prerequisites. The component analysis revealed that the final form of phosphate was mainly the inorganic form such as Fe3(PO4)2·H2O, MgAl2 (PO4)2(OH)2 and CaHPO4·2 H2O in the sludge, accounting for 96.1 ± 4.3 % of the total phosphorus. The XRD pattern indicated that the metal phosphates coexisted with bio-S0 in the sludge, in which 39.1 ± 2.6 % of the phosphorus was highly bioavailable. The study would provide a new way to develop the economical and low-carbon technology for simultaneous removal of phosphorus and nitrogen from wastewater. © 2024 Elsevier Ltd