Pretreatment for Brackish Water Reverse Osmosis of Desalination Plants by Dual-Media Filter

By sieving the Amphistegina tests of average size of 1.2 mm and accumulated from different costs of Red and Mediterranean seas in Egypt and a definite calcite Ooids of mesh size from 0.5–3.0 mm that formed inside a semi–pilot of seawater–softening unit. Recently, we used the dual–media (DM) filter that consisting of Amphistegina tests and fabricated calcite Ooids in removing ionic iron from groundwater. Thereafter, for the first time we have used that recent filtration dual–media as pretreatment technique for brackish water reverse osmosis stage in desalination plants and raw brackish water samples are brought from Al–Qurayyat Governorate, Jouf, Kingdom of Saudi Arabia. Dual filtration media demonstrated an excellent feed water quality improvement producing filtrate of accepted quality to feeding brackish water reverse osmosis (BWRO) membranes at optimum operating conditions of temperature (40 ᵒC) and flow rate (20 l/min). In presence of polyaluminum chloride coagulant, the better silt density index (SDI) of produced filtrate (SDI <3), turbidity of less than 0.1 NTU, total organic carbon (TOC) reducing of higher value reached to 98.6% and the highest value noticed by DM filter in iron removal reached to 100 % in presence of injection of chlorine in the feed water tank.