Maximum recovery from seawater reverse osmosis plants in Kuwait

Membrane scaling is caused by the precipitation of soluble salts as the feedwater is converted to brine. The scaling potential of any feedwater is determined from the feedwater analysis, the conversion of the RO system and the solubility limit of the various salts. In brackish water, calcium carbonate and calcium sulfate are the most common salts for which pretreatment is required. In seawater, calcium carbonate is usually the salt: for which pretreatment is required. Other salts for which pretreatment calculation should be performed to ensure that solubility limits are not exceeded in seawater are barium sulfate, strontium sulfate, calcium floride and silica. The most common method used to prevent scaling in RO plants is removal of deposit-forming constituents, i.e., removing the carbonate and bicarbonate ions from the feedwater by adding acid or chemicals to water to alter the physical or chemical nature or the growth mechanisms of the depositing species i.e. adding scale control inhibitors. The two methods may be used together depending on the nature of the feedwater used. In this paper, solubility product, ion product and the Stiff and Davis Stability Index are calculated for the brine based on the feed of the seawater at Doha-Kuwait and the recovery ratio of the RO plant. The optimal recovery for the RO units at which they can operate safely without adding any scale inhibitor is reported.