A Compact Self-Cleaning Filtration System with Periodic Automatic Back-Flushing for Pretreatment of RO Filtration

The objective of this proposal is to demonstrate the feasibility of an innovative design that combines centrifugal separation, cross-flow filtration (CFF), Dean flow surface cleaning and back-flush techniques into an effective micro-filtration unit. The centrifugal separation is effective in separating particles that have higher specific gravity that the feed fluid down to 20 microns. CFF is especially effective for feed flow with a high amount of colloidal solids. Unlike dead-end filtration, the surface dynamics of CFF does not make the gelatinous colloidal solids extrude through pores which often comprise the performance of filtration. CFF makes use of the shear force parallel to the filter medium to reduce the cake formation on the filter surface. Dean flow is a secondary flow created in a curved flow passage. The resulting flow profile takes the form of a toroidal vortex. The vortex profile generates a high shear rate which acts to transport material such as colloidal solids and fine silts away from the membrane surface. The combination of these features with an automatic back-flushing device forms a compact, self-cleaning and continuously operable unit suitable for pre-filtration in the Navy shipboard reverse osmosis application.