Industrial-scale test of slightly polluted wastewater for reuse in a petroleum refinery

A novel industrial-scale process combined circulating biological aerated filter (CBAF) and sand filter (SF) was used to treat the slightly polluted wastewater for reuse in a petroleum refinery. The process parameters, operation conditions and removal efficiencies of pollutants were investigated. The wastewater was treated by the CBAF process under optimal conditions: the air/water volume flow ratio of about 3:1, the hydraulic retention time (HRT) of 100 min and the backwashing cycle of every 2-3.days. The results show that the average removal efficiency of COD 62.6%, of oil pollutants 71.7%, of NH3-N 92.6% and of SS 97.0%, respectively. And the average effluent concentration of COD, oil pollutants, NH3-N and SS is 14.4 mg-L-1, 0.75 mg-L-1, 0.49 mg-L-1 and 2.4 mg-L-1, respectively. The quality of the effluent can meet the requirements of industrial water reuse.