Comparative analysis of the phosphorus removal characteristics between two-stage and single-stage SBR processes for phosphorus and nitrogen removal

Under normal temperature and sufficient carbon source conditions, with simulated sewage as the treatment object, the characteristics, and advantages of phosphorus removal in the two-stage sequencing batch reactor (SBR) dephosphorization and denitrification process were investigated through comparative analysis. The phosphorus removal characteristics of the single-stage enhanced biological phosphorus removal-sequencing batch reactor (EBPR-SBR) were also discussed. Results showed that the phosphorus removal grade SBR1 of the two-stage SBR phosphorus removal and denitrification system has similar anaerobic phosphorus release and aerobic phosphorus uptake processes to the single-stage SBR. However, the phosphorus removal efficiency of the SBR1 system with low sludge age and high organic load is higher than that of the single-stage SBR system. The rate of specific phosphorus release of the fast phosphorus-releasing segment (0-0.5 h) and the rate of specific phosphorus absorption of the fast phosphorus-absorbing segment (0-1 h) of the SBR1 system are 1.43 and 1.79 times higher than those of the single-stage SBR system, respectively. The effluent total phosphorus (TP) of the single-stage EBPR-SBR system can be no higher than 1.0 mg/L but not 0.5 mg/L. Phosphorus release occurs in polyphosphate-accumulating organisms at the beginning of EBPR-SBR system sedimentation, and the rate of phosphorus release increases over time. The rate of phosphorus release is constant after 40 min of sedimentation. The average rate of phosphorus release is 0.0138 mg P/L min. The final effluent TP of the two-stage SBR phosphorus removal and denitrification system may not be affected by the fluctuation of the effluent phosphorus concentration of the phosphorus removal grade SBR1. Thus, the TP can be easily and stably kept equal to or lower than 0.5 mg/L.