Mass Transport Considerations for Pressure‐Driven Membrane Processes

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Abstract
Numerical simulations and experimental work for evaluating transport mechanisms for colloidal foulants in pressure‐driven membrane systems are discussed. A model for concentration polarization is used to explore the role of ionic strength in determining the distribution of dissolved humic materials near a rejecting membrane. Particle trajectory theory predicts that there should exist a critical particle size above which particles will not deposit on the membrane. For conditions typical of ultrafiltration and microfiltration, which operate in laminar flow and utilize an inside‐out geometry, this critical particle diameter is likely to be in the range of 10–50 μm. Qualitative evidence, based on measurements of permeate flux, supports the theoretical minimum in diffusive back‐transport of particles predicted to occur for particles near 0.1 μm in size.