Ultrafiltration Characteristics of Oil-Detergent-Water Systems: Membrane Fouling Mechanisms

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Abstract
The ultrafiltration characteristics of oil (bilge oil and synthetic based lubricating oil)-nonionic detergent-water (river water and distilled water) systems are evaluated with noncellulosic, tubular membranes. The water flux behavior (membrane fouling) is dictated by the membrane resistance increase due to detergent-membrane interaction and due to surface fouling in the presence of oil-detergent emulsions and suspended solids. Membrane fouling and cleaning requirements depend on the type of oily water systems. Flux drop can be minimized by operating at temperatures above 35°C and/or with short-term membrane depressurization. In all cases the steady-state water flux is a function of the initial membrane water flux. Depending on the oil water systems, water fluxes of 8 to 52 ± 10−4 cm/sec are obtained. Excellent oil rejections are observed in all cases: even with oil-detergent systems, an ultrafiltrate oil concentration of less than 10 mg/1 can be achieved.