Use and Development of Fouling Index in Predicting Membrane Fouling

Membrane fouling has been recognized as an inevitable problem impairing all membrane processes. Fouling control strategies have been adopted to resolve membrane fouling. Fouling index is one of the most popular fouling prediction tools used to predict the fouling potential of feed water in membrane filtration systems. This paper provides an overview of the past and present developments of fouling indices measurement techniques as the membrane fouling prediction tool in reverse osmosis/nanofiltration process. This paper also addresses the possible fouling mechanisms and type of fouling in water filtration processes, start-of-art techniques used to assess fouling mechanisms and methods to predict fouling. The fouling prediction methods highlighted are silt density index (SDI) and modified fouling index (MFI). These fouling indices are correlated with their applications in evaluating the pretreatment efficiency and the flux decline predictions of a feed. Even though there are a number of researchers focusing on the measurement of MFI, the MFI obtained was not correlated to the quality of feed empirically. An appropriate index should be capable of being used as an input to mathematical models for predicting the degree of fouling in a discrete form. The future direction and potential use of fouling indices are also discussed.