Separating biological nutrient removal by EBPR-PN/A process to treat real municipal sewage

The separated biological nutrient removal for treating wastewater has drawn significant interest due to its energy-neutral or energy-positive nutrient removal pathways. Conventional denitrification-based nitrogen removal, an all-in-one process, remains challenging when treating municipal wastewater. This study established a reliable and practical anammox-mediated process in a dual SBR. The first SBR stage enhanced biological phosphorus removal (EBPR) removes influent organics and phosphorus, leaving N for the subsequent partial nitritation/anammox (PN/A); this resulted in a low effluent chemical oxygen demand (COD) of 57.5 mg/L and phosphate of 0.3 mg-P/L. In the second SBR stage, an anammox-mediated process achieved a stable nitrogen removal efficiency of 75.5% and a nitrogen removal rate of 0.23 kg/(m 3 ·d). The second stage operated in anaerobic/oxic/anoxic mode. Adding external organics (COD/N ratio of 0.6) benefits the growth and bioactivities of anammox bacteria by establishing cooperation between anammox and endogenous denitrification in the anoxic stage. Anammox achieved multiple nitrite pathways. The EBPR-PN/A process successfully removed or separated influent carbon/phosphorus and added appropriate external organics to optimize nitrogen removal performance in the subsequent PN/A.