FLUX ENHANCEMENT FOR MEMBRANE FILTRATION OF BACTERIAL SUSPENSIONS USING HIGH-FREQUENCY BACKPULSING

A promising method for reducing membrane fouling during crossflow micr ofiltration of biological suspensions is backpulsing. Very short backp ulses (0.1-1.0 s) have been used to increase the net flux for washed b acterial suspensions and whole bacterial fermentation broths. The net fluxes under optimum backpulsing conditions for the washed bacteria ar e approximately 10-fold higher than those obtained during normal cross flow microfiltration operation, whereas only a 2-fold improvement in t he net flux is achieved for the fermentation broths. A theory is prese nted that is based on external fouling during forward filtration and n onuniform cleaning of the membrane during reverse filtration. The mode l contains an adjustable parameter which is a measure of the cleaning efficiency during backpulsing; the cleaning efficiency found by fittin g the model to the experiments increases with increasing frequency and duration of the backpulses. The theory predicts an optimum backpulsin g frequency, as was observed experimentally. An economic analysis show s that crossflow microfiltration with backpulsing has lower costs than centrifugation, rotary vacuum filtration, and crossflow microfiltrati on without backpulsing. (C) 1998 John Wiley & Sons, Inc.