FLUX ENHANCEMENT IN CROSS-FLOW MICROFILTRATION USING A COLLAPSIBLE-TUBE PULSATION GENERATOR

A dilute suspension of silica particles in water was microfiltered in an unbaffled tubular ceramic membrane. The crossflow was varied periodically at frequencies inducing fluid-dynamic unsteadiness using a novel device for this application, namely a flexible tube compressed to non-circular cross-section by external pressure. This arrangement is unstable and leads to self-sustained oscillations which can be used to add a pulsatile component to a steady flow. With this arrangement, and a time-averaged crossflow sufficient for turbulence in the membrane filter, filtrate flux increases due to pulsation of up to 60% were demonstrated, without systematic optimisation of the pulse parameters. The gain persisted over the entire range of mean transmembrane pressure and crossflow velocity investigated.