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Background Produced 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). Results During the 112 days operation of the MBR at hydraulic retention time (HRT) and sludge retention time (SRT) of 48 h and 80 days 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 0.9 kg 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. Conclusion The 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. © 2013 Society of Chemical Industry

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Mesozoic and Tertiary source rocks and crude oils from six oilfields in the Persian (Arabian) Gulf (Hendijan, Bahrgansar, Abouzar, Nowruz, Dorood and Foroozan) were studied using a variety of organic‐geochemical techniques. Biomarker characteristics were combined with other geochemical data to identify the source rocks which generated the oil in these fields and to reconstruct their depositional environments, and also to characterize the diagenetic and catagenic processes which have occurred. The analyzed oils show a wide range of densities (19 to 39° API) and high sulphur contents. They were generated by Type II‐S organic matter; they are not biodegraded and their maturity level is generally low. Two main oil groups were identified from statistical analysis and can be correlated with different source rocks using age‐specific biomarkers and isotope data. Group 1 oils include those from the Hendijan, Bahrgansar and Abouzar fields and were probably generated by a mid‐Cretaceous argillaceous source rock. Group 2 oils include those from the Nowruz, Dorood and Foroozan fields, and originated from Jurassic to Early Cretaceous carbonate‐rich source rocks.