Oily wastewaters are generated in many industrial processes, such as petroleum refining, petrochemical and food. These oily wastewaters are mainly in the form of oil-in-water (O/W) emulsions. Oil removal requires an understanding of the physical properties and chemical composition of O/W emulsions. Several properties in the stability of an O/W emulsion should be measured for the selection of the appropriate separation process, specifically, surface tension, contact angle, zeta potential and droplet size distribution. Treatment of oily wastewaters is performed by a variety of methods and the degree of oil removal depends on the concentration and physical nature of the oil, droplet size and separation techniques. The purpose of this work is to study oil/water system properties, and techniques for removing oil. These techniques include gravity and centrifugal separations, chemical treatment, flotation, membrane processes, evaporation, activated carbon adsorption and biological treatment. At last, treatment costs and hybrid processes will be covered.
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