Mechanisms by which pulsatile flow affects cross-flow microfiltration

The effect of pulsatile flow on particle deposition during cross-flow microfiltration was studied to establish the degree to which backflushing and shear-rate changes induced during pulsation alter cake formation. The minimum transmembrane pressure and maximum absolute cross-flow velocity derivative were chosen to quantify the backflushing and shear effects, respectively. Experiments were conducted for pulsatile flows with four distinct types of transmembrane pressure and flow-rate waveforms. In the absence of backflushing, the cake resistance was reduced at high values of shear rate, but not significantly affected at low values compared with steady flow. Tests at constant shear rate demonstrated that the cake resistance was reduced when backflushing was imposed on the system. In tests with two transmembrane pressure waveforms, cake deposition was almost completely eliminated by instantaneous backflushing. Although both backflushing and shear-rate changes reduce cake deposition in microfiltration, backflushing achieved the greatest reductions.