SHEAR-STRESS INDUCED EROSION OF FILTRATION CAKE STUDIED BY A FLAT ROTATING-DISK METHOD - DETERMINATION OF THE CRITICAL SHEAR-STRESS OF EROSION

Many authors choose wall shear stress as a fundamental parameter for controlling re-entrainment of particles. Therefore shear stress induced erosion of filtration cake from a colloidal suspension of active carbon is studied using a rotating flat microfiltration membrane. The critical shear stress of erosion, tau* of the macroscopic deposit of solid particles for a given system is thus determined. tau* represents the minimal value of shear stress needed to create erosion. Furthermore the influence of the transmembrane pressure, the thickness of the initial deposit and the pore size on the critical shear stress is investigated and described by empirical fits. Transmembrane pressure and pore size act independently in the same way: the larger they are, the higher tau*. Consequently fouling is more efficiently eliminated at high Delta P-m and large pore size.