Introduction

Membrane fouling refers to a deterioration in membrane performance due to interactions between the feed and the membrane. This typically involves an increase in membrane resistance and an increase in solute rejection. Cake formation and concentration polarisation are technically not considered to be membrane fouling processes, at least in this book. Cake formation is viewed as forming an additional resistance. Concentration polarisation is seen as reducing the driving force for filtration.

There is a vast literature on the subject of membrane fouling but despite this, membrane fouling still remains a largely empirical science. This is not surprising given the huge variation in membrane and feed characteristics that is encountered in membrane filtration processes. Furthermore, the underlying physical processes are complicated, involving solute–solute, particle–particle, solute–membrane and particle–membrane interactions. Identifying which interactions are important is usually very difficult indeed, especially when complex mixtures are involved.