A two-stage sequencing batch reactor (SBR) system was used for treatment of oily wastewater with COD and oil and grease (O&G) concentrations ranging from 1,722–7,826 mg/L and 5,365–13,350 mg/L, respectively. A suitable start-up protocol was developed using gradual increase in oily wastewater composition with methanol as the co-substrate. This strategy enabled a short acclimation period of 12 days for the sludge in the two-stage SBR to adapt to the oily wastewater. After acclimation, the 1st stage and 2nd stage SBRs were able to achieve COD removals of 47.0 ± 2.4% and 95.3 ± 0.5%, respectively. The 1st stage SBR was able to achieve 99.8 ± 0.1% of O&G removal and effluent O&G from the 1st stage SBR was only 6 ± 2 mg/L. The 2nd stage SBR was used to further remove COD in the effluent from the 1st stage SBR. The final effluent from the 2nd stage SBR had a COD concentration of 97 ± 16 mg/L with no detectable O&G content. Thus, a two-stage SBR system was shown to be feasible for treating high strength oily wastewater to meet the local discharge standards.

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