Bio-chemical process for nitrogen and phosphorus removal by draining out anaerobic rich phosphate supernatant in ERP-SBR system

The method of fixed phosphate coming from anaerobic reactor by the auxiliary chemical process is applied in External Recycle Process-SBR (ERP-SBR). This process changes the model of draining out activated sludge in the traditional biological phosphorus removal system to discharge anaerobic poly-phosphate supernatant. This process eliminates the contradiction of control for Solid Removal Time (SRT) in process of biological nitrogen and phosphorus removal. It can obtain high removal efficiency of nitrogen(N) and phosphorus(P) in longer SRT. Experiment results show that: when SRT=50 ~ 80 d, TN=28.6~ 58.3 mg/L, TP=5.5~ 13.5 mg/L in influent , COD≤ 34mg/L, TN≤ 6.02 mg/L, PO43-≤ 0.23 mg/L in effluent . The amount of lime is only 5% of traditional methods. The phosphorus content in the chemical sludge is 12 %~15 % and the recycle of phosphorus can be realized easily.