A Novel Pre-denitrification Phosphorus Removal System: Process, Microorganisms, and Mechanism

To achieve highly efficient and energy-saving wastewater treatment, a novel process involving a pre-anaerobic/anoxic/aerobic nitrification sequencing batch reactor (pre-A2NSBR) was developed herein. Further, this process was used to treat mainstream wastewater, and the functional microorganisms in the process were regulated. The results showed that the dual sludge denitrification and phosphorus removal system achieved simultaneous nitrogen and phosphorus removal, demonstrating a good treatment effect. After 300 days of operation, the system achieved chemical oxygen demand, PO43–-P, NH4+-N, and total inorganic nitrogen removal rates of 85.3%, 91.2%, 99.2%, and 70.5%, respectively, resulting in average effluent concentrations of 29.9, 0.7, 0.5, and 12.4 mg·L–1, respectively. Microbial analysis showed that the main functional microorganisms of the nitrification sequencing batch reactor (NSBR) were Nitrosomonas and Nitrospira, with relative abundances of 13.6% and 15.7%, respectively. The main functional microorganisms of the anaerobic/anoxic/oxic sequencing batch reactor (A2SBR) were Dechloromonas, Candidatus Accumulibacter, and Thauera, with relative abundances of 21.8%, 1.8%, and 6.2%, respectively. The proportion of the nitrification-related enzyme nxrA and the phosphorus-related enzyme ppk1 increased significantly, which was the main reason for the good nitrogen and phosphorus removal efficiency of the pre-A2NSBR system. The above-mentioned results demonstrate that the novel pre-A2NSBR process is a promising technique for energy-efficient wastewater treatment.