Comparative study of continuous and intermittent ultrasonic ultrafiltration membrane for treatment of synthetic produced water containing emulsion

Studies have shown that the ultrasonic is effective in cleaning of fouled membrane and enhancing membrane filtration performance. But the effectiveness also, depends on the selection of appropriate membrane material, membrane geometry, ultrasonic module design, operational and processing condition. In this study, a hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were used and their performance evaluated with synthetic oil-in-water emulsion. The steady-state permeate flux and the rejection of oil in percentage (%) at three different modes were determined. A dry/wet spinning technique was used to fabricate the flat-sheet and hollow fibre membrane (HFMs) using Polyethersulfone (PES) polymer base, Polyvinylpyrrolidone (PVP) additive and N, N-Dimethylacetamide (DMAc) solvent. Ultrasonic assisted cross flow ultrafiltration module was built to avoid loss of ultrasonic to the surrounding. The generation of cavitation, microjets and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration. The mean size of emulsion oil drop become smaller at higher ultrasonic power and the rejection ratio decreases as the size of oil drop decreases. The experimental results suggest that a more economic use of ultrasonic in O/W emulsion ultrafiltration could be achieved using ultrasonic energy intermittently rather than continuously.