Treatment of oil contaminated wastewater in a membrane bioreactor

Activated sludge processes are frequently applied to treat industrial effluents. The membrane-bioreactor (MBR) is a modification of this conventional process, where the activated sludge is concentrated in a bioreactor which is connected to a cross-flow ultrafiltration membrane unit. Trials in a MBR with a high activated sludge concentration of up to 48 g l−1, showed that oily wastewater also containing surfactants was biodegraded with high efficiency. During the different loading stages of the MBR operation a removal rate of 99.99% could be achieved for fuel-oil as well as lubricating oil at a hydraulic retention time of 13.3 h. The maximum biodegradation of fuel oil amounted to 0.82 g hydrocarbons degraded per day, and g MLVSS and average values of 0.26–0.54 g hydrocarbons g−1MLVSS d−1 could be achieved. The average removal of COD and TOC during the experiment was 94–96% for fuel oil 97, and 98% for lubricating oil, respectively. Due to the high removal efficiency of oily pollutants and the complete retention of suspended solids by the ultrafiltration unit, the MBR system shows good potential for application in industry for process wastewater recycling purposes.