REVERSE OSMOSIS OF REFINERY OILY WASTEWATER EFFLUENTS

Laboratory-scale reverse osmosis (RO) studies were carried out to determine feasibility of the process for treatment of Tehran refinery oily wastewater. The effects of transmembrane pressure (TMP), cross flow velocity (CFV), temperature and pH on permeation flux and separation performance of the thin film composite (TFC) polyamide (PA, type UTC-70UB) RO membrane were investigated. At original effluent composition, high rejection of TDS (87.0%), COD (95.0%), BOD5 (95.3%), TOC (90.0%), turbidity (81.8%) and oil and grease content (86.1%) along with complete rejection of color, free oil and TSS were achieved with a reasonably high flux of 50 L/m2h. Permeation flux was found to improve with increasing TMP, CFV and temperature at constant feed concentration but rejection decreased slightly. The pH effects were found to be complex; by increasing acidic and basic nature of the feed, permeation flux was found to increase and rejection to reduce. The results showed that, RO is very suitable for treating and recycling refinery oily wastewater effluents. Also, fouling of the membrane completely followed Hermia's model (cake filtration mechanism).