In the pretreatment preceding desalination, fine particles in seawater are removed using cross-flow and rotating-disk dynamic filtration. The effects of operating conditions, such as cross-flow velocity, transmembrane pressure, disk rotation speed, and the clearance between the disk and the membrane, on the filtration flux, cake properties, and power consumption are discussed. An increase in the cross-flow velocity or transmembrane pressure leads to higher filtration flux. The filtration flux and cake thickness can be accurately estimated using a force balance model for the particle deposition associated with the basic filtration equation. A dynamic filtration module is used to increase the filtration flux. The particles are easily swept away from the membrane surface because of the shear stress generated by the rotating disk. The filtration flux therefore increases by either increasing the disk rotation speed or reducing the clearance between the disk and the membrane. The specific filtration flux, defined for indicating the power effectiveness, decreased with an increase in the disk radius, an increase in the disk rotation speed, or a decrease in the clearance between the disk and the membrane because of a drastic increase in power consumption. A smaller disk is more effective in saving energy.
Journal of the Taiwan Institute of Chemical Engineers 62, pp.45-53