Seawater pretreatment by continuous sand filter for seawater RO (reverse osmosis) desalination plant

Abstract

Sand filtration is conventionally applied to the preteatment of raw seawater in the RO desalination plant to maintain the seawater quality within the low SDI (Silt Density Index) level. However, the conventional fixed bed type has some difficulties of unstability of the filtrate quality in the backwash period and complicated operation sequence. In solving these difficulties, the applicability of the continuous sand filter has been studied with four years operation at Kure, Japan. The operational result shows that the filtrate is kept in the SDI level of four (4) which is applicable to the seawater RO desalination plant. This continuous sand filter has the advantage of stability, operation and energy saving as compared with the conventional batch type so that our developed continuous sand filter will improve plant economics for the seawater RO desalination plant.