NONLINEAR FLOW THROUGH COMPRESSIBLE MEMBRANES AND ITS RELATION TO OSMOTIC-PRESSURE

The application of hydrostatic pressures to porous membranes causes a reduction in the membrane permeability due to compaction. We present a mechanism whereby both the hydrodynamic and the osmotic pressure contribute to the compaction of the membrane and the concomitant change in flow resistance. The result is a better understanding of flow through compressible membranes than is reflected in the literature. A mathematical model is used to illustrate how this concept can produce non-linear and asymmetric flow even in a simple homogeneous membrane. Some implications are outlined for flow through membrane systems, including the effect of flow-resisting boundary layers such as fouling layers.