Practical use of standard pore blocking index as an indicator of biofouling potential in seawater desalination

A practical approach to evaluate the biofouling potential of feed waters for seawater reverse osmosis (SWRO) was investigated. Assimilable organic carbon (AOC) and modified fouling index through an ultrafiltration 10 kDa membrane (MFI-UF10) were measured for seawater and pretreated seawater. The pretreatments adopted were dual media filtration (DMF) coupled with coagulation and submerged membrane adsorption bioreactor (SMABR). Low molecular weight neutrals (LMW-N) responsible for biological growth (or biofouling) constituted the major component in seawater and pretreated seawater. A very good linear relationship was observed between AOC concentration and LMW-N concentration. A detailed study on various fouling indices revealed that standard blocking index (Ks) calculated from MFI-UF10 correlated with AOC concentration. This indicates that MFI-UF10 test can serve as a preliminary indicator of AOC and LMW-N (which are biofouling precursors). MFI-UF10 can also be used directly in desalination plants.