Thermophilic membrane bioreactor for the treatment of oily wastewater

The membrane bioreactor (MBR) as an alternative method for simultaneous biodegradation and separation of oily water has received more attention, recently. Normally the MBR works at ambient temperature; therefore, the yield of biodegradation recalcitrant components is low. Increasing temperature improves the efficiency of degradation and reduces the amount of produced sludge. In this study the performance of an aerobic thermophilic membrane bioreactor (MBR) for treating oily wastewater has been investigated. In batch conditions (without applying the membrane), a comparison between COD removal in mesophilic and thermophilic conditions was done. In thermophilic conditions COD and oil removal efficiency were more than 90% when the hydraulic retention time (HRT) of the system was 15 and 18 hours. In continues mode, when the MBR was operated with the average MLSS of 6500 mg/l, COD and oil removal efficiency reached near 94% and 96%, respectively. Decreasing HRT led to accumulation of oil, therefore, the concentration of oil in the bioreactor will exceed than concentration in the influent. Shorter HRT increased the propensity of the membrane to fouling. The optimum retention time was 8 h and in this condition COD and oil removal efficiency were 93% and 96%, respectively.The MBR system provided stable effluent quality against shock loading.