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ab s t r ac tTreatment of the oily and greasy wastewater of Tehran refinery using an ultrafiltration (UF) system was experimentally studied. In the experiments, a polysulfone (PS) (30 kDa) and a polyacrylonitrile (PAN) (20 kDa) and the API wastewater of Tehran refinery as membranes and feed were used, respectively. Effects of different operating parameters such as transmembrane pressure (TMP), cross flow velocity (CFV), temperature and pH on permeate flux, fouling resistance (R f ) and rejection were studied. According to the results, the optimum operating conditions of the UF process were found as following: TMP (3 bar), CFV (1 m/s), operating temperature (40°C) and pH (9). Performance of the both membranes for the wastewater treatment was compared. The PAN membrane showed higher rejection, permeate flux and less R f than the PS membrane. Also, when using the PAN membrane, concentration polarization phenomenon and consequently gel layer formation took place quicker. A cleaning procedure was proposed using a metal chelating agent (EDTA) and an anionic surfactant (SDS) which was able to regenerate the fouled UF membranes effectively by optimizing chemical (pH) and physical (cleaning time, CFV and temperature) conditions. Analysis of the UF process showed 99.7%, 77.2%, 63.3%, 65.4%, 29.8%, 100% and 99.5% reductions of oil and grease content, TOC, COD, BOD5, TDS, TSS and turbidity, respectively. Long term experiments confirmed that UF using the PAN membrane is effective for treatment of oily wastewater produced from refinery processes. A comparative study also showed that UF is more effective than the conventional biological method.

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Oily wastewater is produced in oil refining processes. This waste is usually treated by a number of physical, chemical, and biological techniques in water treatment units of oil refinery before being disposed in environment or reused as agricultural water. One of the treatment techniques for oil separation from wastewater is membrane filtration. This paper presents the performances of hydrophilic microfiltration (MF GRM) and ultrafiltration (UF GRM) polymeric membranes challenged with synthetic feed (gas oil dispersed in water) and oily wastewater effluent of American Petroleum Institute unit in refinery. A comparison was carried out under optimum conditions and in cross-flow mode in laboratory scale. The effects of operating parameters (i.e. pressure and cross-flow velocity) on flux and rejection were elucidated. The flux of MF GRM membrane for real feed within the first 2 h of filtration was low compared with synthetic feed because of the presence of solid and colloidal particles in the real feed. The oil rejection (around 99%) for synthetic feed was higher compared with real feed. Similar trend was found for both UF GRM and MF GRM membranes.