Unstable secondary oil water emulsion treatment using ultrafiltration: fouling control by backflushing

Ceramic membranes with different characteristics and pore size distribution s were evaluated for the treatment of an unstable secondary emulsion. The e xperimental studies were undertaken to investigate the optimum operating co nditions (forward and reverse backflushing time, pressure, velocity and fee d concentration) to obtain the best permeate flux. Backflushing was applied to reduce the formation of a gel polarization layer and membrane fouling. The optimum forward filtration and reverse filtration time were found to be 1 min and 0.7 s, respectively. Applied pressure, velocity and feed concent ration also have an important influence on the flux. With hydrophobic membr anes, flux was found to be lower than with hydrophilic membranes, indicatin g that oil was easily wetted on the hydrophobic membrane surface and induce d more fouling of the membrane. The contamination of the permeate with oil was observed when using 0.5 mu m pores as the operating pressure was then h igher than capillary pressure. Moreover, oil droplet sizes were bigger than in the feed as a result of the coalescence of oil drops as they passed thr ough the membrane pores. (C) 1999 Elsevier Science B.V. All rights reserved .