Innovative combination of Fe2+-BAF and ozonation for enhancing phosphorus and organic micropollutants removal treating petrochemical secondary effluent

Two sets of BAF - ozonation systems, with (System-A) and without (System-B) Fe2+ dosing into BAF, were used for organic micropollutants (OMPs) and phosphorus removal in the advanced treatment of petrochemical secondary effluent. Pilot scale study showed that when the influent COD, TP and TSS were 73.0, 1.40 and 24.6 mg L−1, the effluent COD, TP and TSS were 48.9, 0.32, 7.78 mg L−1 for System-A with the ozone and Fe2+ dosage of 25 mg L−1 and 0.08 mmol L−1, and 60.2, 1.16, 6.44 mg L−1 for System-B with the ozone dosage of 25 mg L−1. The dosage of Fe2+ into the BAF significantly enhanced the TP and OMPs removal ability. Exactly, the residual Fe2+ in the BAF-A effluent stimulated the catalytic ozonation in the following ozone unit. Therefore, the OMPs removal in System-A was obviously better than that in System-B. The dosage of Fe2+ from 0.02 to 0.10 mmol L−1 had slight adverse effect on the biofilm activity in BAF. Based on the TP and OMPs removal ability, the System-B is selected as a proposed process for the advanced treatment of petrochemical secondary effluent.