Simultaneous removal of nitrogen and phosphorus by a novel aerobic denitrifying phosphorus-accumulating bacterium,...

A novel denitrifying phosphorus-accumulating bacterium was isolated from contaminated sediment and identified as Pseudomonas stutzeri ADP-19. Bio-safety assays demonstrated that the strain was γ-hemolytic, antibiotic-sensitive, and had no decarboxylase activity. It removed 96.5% of NH₄⁺-N and 73.3% of PO₄^3--P (at initial concentrations of 100 mg/L and 20 mg/L) under aerobic conditions, and the corresponding maximum removal rates were 3.44 and 0.41 mg/L/h, respectively. Nitrogen removal was achieved through a fully nitrification-denitrification pathway [NH₄⁺-N → NH₂OH → NO₂^--N → NO₃^--N → NO₂^--N → (N_xO) → N₂], while phosphorus removal mainly depended on the phosphate assimilation and the excessive poly-P accumulation. Strain ADP-19 also showed a strong salt tolerance within a wide salinity range of 0-5%. The enhanced biological treatment of anaerobic-digested wastewater in a sequencing batch reactor (SBR) indicated that the strain improved the microbial diversity of the activated sludge and significantly enhanced the nitrogen and phosphorus removal efficiency.