Mineralization Process Research Of Desalinated Water

Among the measures of solving the shortage of global freshwater resources, seawater desalination technology is very important, and its application is more and more extensive. However, the desalinated water directly used as drinking water, lacks the mineral elements of Ca²⁺ and Mg²⁺, which are essential for our bodies. Moreover, the desalinated water is unstable, strong corrosive, and may cause red water events. The measure for improving the desalinated water is mineralization, which can add the content of mineral and alkalinity, make the water stable and non-aggressive, and agree to the drinking water standards.The process that based on sulfuric acid dissolving limestone, and calcium exchange with magnesium, which adds magnesium ions on the base of calcium ion added, is very perfect mineralization process at present. This paper used devices of sulfuric acid dissolving limestone and ion exchange to investigate the feasibility of desalinated water mineralization, to discuss the effect of mineralization and operation parameters, and to provide foundation for industrial mineralization.The mineralization effect of acidulated water dissolving limestone is obvious. When we use sulfuric acid adjusting the pH of desalinated water to about 2.00, the Ca²⁺ concentration of desalinated water is above 300mg/L after mineralization. Under experiment condition, the effect of mineralization increases as limestone packing height rise, while decreases with the flow of desalinated water increase, and decreases follow the rise of limestone particle size, and increases as the temperature increases. The value of pH is very important factor of mineralization effect. Controlling the value of pH under 2.00 can clearly add the content of calcium ion.The process of ion exchange can achieve replacement between calcium and magnesium. Brine used as resin regenerant after calcium exchanged with magnesium, can make the exchange performance of resin recover to initial level.The desalinated water was only treated by acidulate dissolving limestone and ion exchange between calcium and magnesium, then Ca²⁺, Mg²⁺, pH, Alkalinity, LSI and CCPP aren't all reach to requirement. While the desalinated water can be reached to stability through NaOH adjusted. After mineralization and adjusting pH, Ca²⁺ of the desalinated water is 40mg/L, Mg²⁺ is 12mg/L, Alkalinity is about 120mg/L, pH is between 8.0 and 8.5, LSI is between 0 and 0.5. The desalinated water meets the drinking water standards, and is stable and non-corrosive.