Treatment of secondary effluent from a petrochemical wastewater treatment plant by ozonation‐biological aerated filter

BACKGROUD Secondary effluent collected from a petrochemical wastewater treatment plant was treated by ozone–biological aerated filter (O3‐BAF) to investigate and evaluate the performance, organics and genotoxicity removal characteristics of this combined advanced treatment process. RESULTS The average dissolved organic carbon (DOC) of the secondary effluent was approximately 23 mg L−1. When the ozone dosage was 10 mg L−1 and the contact time was 4 min, the DOC removed by O3‐BAF was approximately 9 mg L−1 during which 37% was removed by ozonation and 63% by BAF. The ozonation changed the percentage of the small molecular size organics (< 1 k) increasing from 54% to 67%, and the high molecular size organics (> 100 k) decreasing from 26% to 8%. More than 85% of the genotoxicity of the chemical secondary effluent was removed in the ozonation unit. The genotoxicity of the BAF effluent was less than 0.71 µg‐4‐nitroquinoline‐N‐oxide L−1. CONCLUSION Ozonation can change the organics molecular size, increase the biodegradability and obviously reduce the genotoxicity of petrochemical secondary effluent. The O3–BAF process is suitable for the advanced treatment of petrochemical secondary effluent.