ABSTRACT
Recently, several methods were developed to monitor biological/organic fouling potential in seawater reverse osmosis (SWRO) systems such as bacterial growth potential (BGP). The correlation between these methods and biofouling in SWRO systems has not been demonstrated yet. In this research, the relation between BGP in SWRO feed water and SWRO membrane performance was investigated. For this purpose, the pre-treatment of a full-scale SWRO plant including dissolved air flotation (DAF) and two stage dual media filtration (DMF) was monitored for 5 months using different indices for particulate (silt density index and modified fouling index) and biological/organic fouling (BGP, orthophosphate, chromatography organic carbon).
Results showed that particulate fouling potential was well controlled through the SWRO pre-treatment as the measured indices in the SWRO feed water were below the recommended values. DAF in combination with coagulation (1 – 5 mg-Fe+3/L) achieved 70 % removal of orthophosphate, 50 % removal of BGP, 25 % removal of biopolymers, and 10 % removal of humic substances. Higher BGP in the SWRO feed water corresponded to a higher normalized pressure drop in the SWRO, suggesting the applicability of using BGP of SWRO feed water as a biofouling indicator in SWRO systems. However, to validate this conclusion, more SWRO plants with different pre-treatment systems need to be monitored.
