[Experimental study on the effect of COD/P ratios and phosphate recovery on a BNR system]

Based on a BNR system--BCFS, the effect of COD/P and phosphate recovery on the BCFS process was experimentally investigated. The results indicate that a higher P-removal efficiency (87%) and a good P-effluent quality (< or = 0.8 mg x L(-1)) could be maintained at COD/P ratios higher than 24. When COD/P was reduced below 24, the P-removal efficiency was suddenly decreased down to 62% and the P-effluent went up to 5 mg x L(-1). Under the circumstance, chemical phosphate recovery in the side-stream of anaerobic supernatant was combined with bio-P removal. When the side-stream increased up to 30%, the P-effluent went back to < 1 mg x L(-1), with a corresponding phosphate recovery efficiency of 54%.