[Inhibitory Effect of Phenol on Phosphorus Removal Performance of an EBPR System]

An SBR reactor was operated to study the inhibitory effect of different concentrations of phenol (5, 10, 30, 50, 100, 150, and 200 mg·L^-1) on the phosphorus removal performance of an EBPR system. The results showed that when the phenol concentration was no higher than 50 mg·L^-1, the removal efficiencies of COD and PO₄^3--P were above 85%. The system showed efficient pollutant removal performance. However, when phenol was higher than 100 mg·L^-1, phosphorus removal performance of the reactor decreased drastically. When phenol concentration was 200 mg·L^-1, the system lost phosphorus removal performance after only 22 cycles. The average COD removal efficiency dropped to 61.3%, and high removal performance recovery was not observed in the short term. Meanwhile, it was found that long-term dosing of phenol inhibited phosphorus removal of the sludge subjected to EBPR. Furthermore, the inhibition on aerobic phosphate uptake was greater than that on anaerobic phosphate release. In addition, the limited sludge bulking disappeared gradually owing to acclimation of the sludge to toxicity with a low phenol concentration (≤ 50 mg·L^-1). However, high concentration of phenol induced sludge bulking was difficult to recover. The short-term impact experiments showed that effluent COD and phosphorus fluctuation caused by phenol could be recovered gradually by removing phenol, suggesting that the inhibitory effect of phenol on phosphorus removal was reversible.