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

Abstract BACKGROUD Secondary effluent collected from a petrochemical wastewater treatment plant was treated by ozone–biological aerated filter ( O 3 ‐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 O 3 ‐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 O 3 –BAF process is suitable for the advanced treatment of petrochemical secondary effluent. © 2014 Society of Chemical Industry