Removal of micropollutants during biological phosphorus removal: Impact of redox conditions in MBBR.

Further biological polishing of micropollutants in WWTP effluents is limited by the lack of available carbon for cometabolic degradation. Metabolism of polyhydroxyalkanoates (PHAs) stored intracellularly during enhanced biological phosphorus removal (EBPR) could serve as carbon source for post-denitrification and micropollutant cometabolism. The removal of nine micropollutants (i.e., pharmaceuticals and corrosion inhibitors) was investigated by using Moving Bed Biofilm Reactors (MBBRs), selecting phosphorus (PAO) or glycogen (GAO) accumulating organisms under different redox conditions. Three laboratory-scale MBBRs were operated in sequencing-batch mode under cyclical anaerobic and aerobic/anoxic conditions for phosphorus removal. Batch experiments were performed to evaluate the biodegradation potential of micropollutants along with the utilization of internally stored PHA. Experiments showed that aerobic PAO were able to efficiently remove most of the targeted micropollutants. The removal of benzotriazole, 5‑methyl‑1H‑benzotriazole, carbamazepine, ketoprofen and diclofenac occurred simultaneously to phosphorus uptake and terminated when phosphorus was no longer available. Denitrifying PAO and aerobic GAO exhibited lower removal of micropollutants than aerobic PAO. Degradation profiles of stored PHA suggested a diverse utilization of the different fractions of PHA for phosphorus and micropollutant removal, with PHV (poly 3‑hydroxyvalerate) most likely used for the cometabolism of targeted micropollutants.