To study the mechanism of particle deposition in crossflow filtration, hydrodynamic forces exerted on a spherical particle touching the surface of filter medium are analyzed to derive the critical selective cut-diameter of the deposited particles under various crossflow velocities and filtration rates in a crossflow filtration system. Experimental data of turbulent crossflow filtration of dilute light calcium carbonate suspension agree with the prediction of this theory within 30% error under the crossflow velocity of from 0.57 to 1.14 m/s. Equations to estimate the characteristics of crossflow filtration, such as steady-state filtration rate and average specific resistance of cake, are also presented.

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This study employs a computerized axial tomography scanner (CATSCAN) to measure the spatiotemporal distributions of solidosity for a clay slurry flocculated with a cationic polyelectrolyte. Flocculation produces fast-settling sediment and a clear supernatant. Limited data revealed the finite role of sludge plasticity on rheological characteristics. However, owing to the deterioration of the sludge network structure during settling, the purely elastic constitutive equations properly interpreted the final sediment data. The null-stress solidosity was estimated using three different methods. Polyelectrolyte flocculation renders a low attainable solidosity at the settler bottom, the low null-stress solidosity, and a less-compressible sediment. Most of the sedimentation processes considering well-flocculated slurries is governed by sedimentation compaction. The solid flux in the sediment is not a unique function of solidosity.