Industry News

seawater desalination technology

2016-04-04 22:43:49

        The purpose of seawater desalination pretreatment is to remove the particles of sand, colloid, microorganism and other impurities in the surface water, and to ensure the long-term stable operation of the reverse osmosis system. In the design of Seawater Pretreatment process, the water quality of the treated water should meet the requirements of the water quality of the reverse osmosis membrane element.
        Pretreatment process of sea water desalination equipment
        1, coagulation filtration
        Coagulation filtration is designed to remove colloid, suspended impurities and reduce the turbidity of seawater. As the sea water ratio is significant, pH value is higher, the project uses FeCl3 as coagulant, dosage in 1 ~ 2mg/L. The mixer, colloidal impurities in iron and water formed larger flocs, then the mechanical filter, water quality pollution index (SDI15) less than 5, the turbidity is less than 1.
        The first phase of the project is configured with 9 sets of mechanical filter, single mechanical filter design diameter 3200mm, lined with 5mm natural rubber, coated with anti-corrosion ship paint, using the bottom water cap structure, filled according to the stipulation gradation of the filter media, a single filter design water quantity for 67m3/h. In order to save water consumption, using reverse osmosis concentrated water as filter backwash water. The system configuration of the concentrated pool, backwash water pump and the blower. Air scrubbing water backwashing flow rate was 16L/m2.s, 15L/m2.s.
        2, the elimination of residual chlorine dosing and prevent reverse osmosis membrane fouling precipitation
        In the presence of free chlorine in the seawater, the performance of the reverse osmosis membrane element can be reduced, so that the free chlorine <0.1mg/L must be controlled before the seawater enters the reverse osmosis membrane. Through the metering pump investment and 1.5-2mg/L sodium bisulfite, seawater chlorine reacted with sodium bisulfite, the formation of acid and neutral salt, in order to remove the residual chlorine on the influence of reverse osmosis membrane.
Seawater containing high concentrations of Ca2+, Mg2+, HCO3-, SO42- plasma, in the process of reverse osmosis desalination, seawater is concentrated, easy to form the precipitation of insoluble inorganic salts on the surface of the reverse osmosis membrane. According to the water recovery rate of the raw water and the reverse osmosis device, the Stiff & Davis index was calculated to determine the trend of fouling precipitation. The water treatment agent was added to the water before entering the reverse osmosis device. Through the comprehensive evaluation of several scale inhibitor inhibition effect and price, selection of sulfuric acid as inhibitor, the dosage is 15 ~ 20mg / L, control of seawater pH value 7.0 ~ 7.5, can effectively prevent water insoluble inorganic salts in the reverse osmosis membrane formed on the surface of the fouling deposits.

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