Process factors during removal of oil-in-water emulsions with cross-flow microfiltration

The results from an experimental study on the separation of oil from oily waters are presented. The investigations were focused on the problem of the process factors that affect the permeate flux. The following parameters were taken into account: membrane type, module type, operating conditions such as transmembrane pressure, recirculation velocity, feed concentration and temperature. The continuous monitoring of the permeate flux enabled the flux decline to be observed in each case. The experimental method compared the cross flow with dead-end runs under various operating conditions. The performance of the polymeric membranes Millipore 0.45 μm and Gelman 0.1 μm were compared with the ceramic membranes Ceramesh 0.1 μm and Membralox 0.1 μm. The flat plate module Pleiade and tubular module membralox were used. The flux-time curves were analyzed using a modified form of Hermia's method and the surface renewal concept to investigate the reason for flux decline. The conditions under which pore-blocking is important were identified using a combination of pore blocking and cake filtration formulae. The results of the experiments show that the ceramic membranes demonstrated better performance. The permeate flux was higher and more stable. Ceramic membranes were less susceptible to fouling and much more sensitive to control by means of operating conditions.