Sludge characteristics and performance of a membrane bioreactor for treating oily wastewater from a car wash service station

In this study, a membrane bioreactor (MBR) with hollow fiber membrane modules was developed to potentially treat oily wastewater from a car wash station. The property and characteristics of sludge, as well as its hydrophobicity and membrane permeability, were investigated in detail. The MBR system was operated for approximately 120 d. It was found that good organic matter removal efficiencies, indicated by both COD and oil and grease results, were achieved at 90% and 88%, respectively. The specific oxygen uptake rate of the sludge in the MBR reactor was observed to be low (2.3–4.7 mg O2/g MLVSS·h), indicating low biological activity of the sludge in the MBR system. The permeability rapidly reduced from 90 L/m2·h·bar to below 5 L/m2·h·bar during the operation, indicating the occurrence of membrane fouling. After acid and alkali washing, a recovery rate of over 96% of the initial membrane permeability was achieved. The results proved the ability of the MBR to treat the oily waste water from a car wash service station.