Development of softening and ballasted flocculation as a pretreatment process for seawater desalination through a reverse osmosis membrane

Abstract Efficient desalination through a reverse osmosis (RO) membrane requires the prior removal of blockade-causing substances from raw seawater. To achieve ultrahigh-speed processing pretreatment process for seawater RO desalination, we combine traditional softening with ballasted flocculation (SBF) Ca 2+ and Mg removal. An alkaline mixture Ca(OH) 2 Na CO 3 was most suitable agent reduced amount generated sludge. This treatment simultaneously removed suspended solids bacteria actual The settling velocity via extremely low. Under optimum conditions desalinating using an anionic polymer flocculant microsand, exceeded 3.5 cm/s, 833 times higher than that without flocculation. sludge after standing min 76.5% lower in SBF conventional softening. silt density index treated met water-supply standard membranes (i.e., <3.0). Furthermore, SBF-generated exhibited considerably improved dewatering property obtained can efficiently quickly remove causative fouling seawater, thereby improving treatability provides new membranes.