New concept to characterize seawater quality for RO plant design and operation

Characterization of seawater quality is crucial to determine the selection and design of pretreatment process as well as to manage membrane fouling in seawater reverse osmosis (SWRO) plants. In some cases, conventional seawater quality parameters are limited in explaining the regional variations of raw seawater and/or in predicting the extent of membrane fouling because of poor correlations between the amounts of impurities in seawater and the resultant membrane fouling. In this study, four seawater quality parameters (P-MFI, C-MFI, PROTEIN and HUMIC) are newly employed to investigate whether those parameters could overcome the current limitations of conventional parameters. Seawater samples have been collected periodically from five different SWRO plants and then analyzed by multiple membrane array system to obtain the two different MFI values and by fluorescence spec-trophotometer for PROTEIN and HUMIC quantifications. Statistical analyses of seawater quality data from the SWRO plants showing the different extent of membrane fouling suggest that those parameters are useful to estimate membrane fouling by all types of impurities such as particles, colloids and organic matters in seawater. In addition, the four suggested parameters (P-MFI, C-MFI, PROTEIN and HUMIC) could better specify the regional differences of seawater quality and the changes of impurities from raw seawater to RO feedwater according to operating conditions, which would be the basis to establish the practical guidelines for a pretreatment design and an efficient operation of SWRO plants.