BackgroundProduced water (PW) is the most important wastewater of the oil industry and if disposed of without adequate treatment can cause serious environmental pollution. Biological treatment is one option explored in recent years for treatment of PW but traditional biological processes potentially fail when the salinity level of the PW is high. In the present study, a halophilic bacterial consortium was employed for treatment of high salinity synthetic PW in a membrane bioreactor (MBR). ResultsDuring the 112days operation of the MBR at hydraulic retention time (HRT) and sludge retention time (SRT) of 48h and 80days respectively, there was a consistently low turbidity in the MBR effluent. Oil and grease (O&G) content of the effluent was also consistently below international limits for discharge to the sea or re-injection to oil wells. With increase in organic loading rate from 0.3 to 0.9kg COD m(-3) d(-1), O&G removal efficiency increased from 89.2% to 95.5% whereas chemical oxygen demand (COD) removal efficiency (c. 83%) did not change. Also, the transmembrane pressure during operation of the MBR remained in the range 1-2 kPa. ConclusionThe results of the present study indicate the very good potential of the MBR, both in terms of removal performance and membrane fouling, for treatment of high salinity PW. (c) 2013 Society of Chemical Industry