Effective Diameter for Shear-Induced Diffusion for Characterizing Cake Formation in Crossflow Microfiltration at Polydisperse Conditions

During crossflow microfiltration, formation of cake layer on the membrane inhibits the filter performance. Previous studies on cake formation have focused on the monodisperse conditions, although most field applications are under the polydisperse conditions. In this study, microfiltration experiments were conducted to investigate the effect of particle size on cake formation, especially, at polydisperse conditions. Kaolin and two kinds of CaCO3 were used as polydisperse particles and a polysulfon hollow fiber microfilter was used as the membrane for the experiment. To describe the effect of particle size on cake formation at polydisperse conditions, effective diameter for shear-induced diffusion ~EDSD! was introduced as a representative particle size. Statistical analyses of the experimental results showed that EDSD can be used in quantifying the potential of cake formation at polydisperse conditions, and the larger the EDSD, the thinner the cake layer. EDSD was an imperative indicator which showed the potential of cake formation at polydisperse conditions quantitatively and can be applied to find efficient strategies for reducing the cake layer. DOI: 10.1061/~ASCE!0733-9372~2005!131:6~865! CE Database subject headings: Environmental engineering; Water treatment; Membrane processes; Fouling; Crossflow; Filtration.