Impact of Cr(VI) on P removal performance in enhanced biological phosphorus removal (EBPR) system based on the anaerobic and aerobic metabolism

Influence of Cr(VI) on P removal in enhanced biological phosphorus removal (EBPR) system was investigated with respect to the composition of poly-phosphate-accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs), the transformation of poly-β-hydroxyalkanoates (PHA) and glycogen, enzymes’ activities, and the intracellular Cr. Whether EBPR system could revive after Cr(VI) shock was also explored. Results showed P removal performance was completely inhibited by Cr(VI) with the concentration more than 5 mg L−1. PAOs were more sensitive to Cr(VI) than GAOs and the other bacteria were. PHA consumption, glycogen synthesis and adenylate kinase’s activity had been inhibited by 5 mg L−1 Cr(VI). Both adenylate kinase’s activity and P removal efficiency were negatively correlated with the intracellular Cr. Recovery experiments revealed that P removal performance with 5 mg L−1 Cr(VI) shock could revive after a 2-day recovery treatment, while systems with high level Cr(VI) (20 and 60 mg L−1) shock could not.