Development of a new blocking model for membrane fouling based on a composite media model

The pore constriction (or standard blocking) model is widely used to describe the filtration behavior for a wide range of suspensions/solutions even though the underlying assumption of a uniform reduction in the radius of non-interconnected cylindrical pores is unlikely to be valid in almost any system. This short communication presents an alternative blocking model based on a description of the effective permeability of a fouled membrane accounting for the flow around and under the deposited foulant through the interconnected pore structure of the membrane. The resulting filtration equation gives linear fouling relationships that are very similar to those for the classical pore constriction model, including the slope on a derivative plot, providing a possible justification for the successful use of the pore constriction formalism in describing the flux decline behavior in many membrane systems. In addition, this new blocking model is readily extended to the case where the deposited foulant is permeable to flow. This new composite media blocking model not only provides useful expressions for the rate of flux decline during constant pressure filtration, it also provides insights into the underlying physical mechanisms controlling fouling in membrane systems.