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-S-0 (>25 mg/L) were two prerequisites. The component analysis revealed that the final form of phosphate was mainly the inorganic form such as Fe-3(PO4)(2)<middle dot>H2O, MgAl2 (PO4)(2)(OH)(2) and CaHPO4<middle dot>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-S-0 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.