Review of the effect of selected physicochemical factors on membrane fouling propensity based on fouling indices

Membrane fouling is one of the major drawbacks for membrane-based technologies because it leads to severe flux decline which requires the fouled membrane to be cleaned and replaced on a regular basis. A systematic approach that is capable of providing early diagnosis is essential to control membrane fouling. Fouling index is a measure for fouling propensity of water in reverse osmosis applications. The present paper focuses on the review from the existing literature of the various fouling indices, i.e. SDI and MFI associated with a number of selected physicochemical factors. Despite of the fact that the membrane fouling problems and their forming mechanisms have been studied by numerous researchers, the evaluation on the contributing factors towards the fouling propensity is still remained unclear. Membrane fouling propensity can be influenced by: membrane morphology (i.e. surface porosity, membrane material, membrane hydrophobicity, membrane molecular cut-off, pore size), feedwater composition (i.e. ionic strength, pH, types and concentrations of feed), and hydrodynamic conditions (i.e. crossflow velocity, permeate flux and temperature). These factors were discussed in great detail in the present review.

► Membrane fouling is one of the major drawbacks for membrane-based technologies.
► Fouling index has been used to measure fouling propensity in RO/NF applications.
► Fouling indices, i.e. SDI and MFI and effects of different factors are reviewed.
► The important contributing factors towards the fouling propensity were discussed.