Coagulation purification of natural water with iron oxide salts

Summary

The efficiency of using ferric chloride and ferric sulphate for coagulation purification of natural and model water depending on the turbidity, color, alkalinity of the source water and flocculation duration is considered. It is shown that for the purification of turbid water, the doses of coagulants related to the iron ion do not depend on the type of coagulant and increase with rise of the turbidity of the purified water. Power dependence of the dose of ferric chloride on the turbidity of the source water was determined. Ferric chloride is the most effective coagulant for reducing turbidity and color, simultaneously providing for the standard concentration of iron ions in purified water. The higher efficiency of ferric chloride compared to ferric sulphate is determined by the presence of polyoxychloride complexes in ferric chloride solutions. It has been established that the main contribution to the reduction of turbidity of water coagulated with iron oxide salts is made by alkalinity that determines the rate and amount of insoluble products of hydrolysis of iron oxide salts. Using the example of coagulation purification of colored waters from different water sources using iron oxide salts, it has been shown that with an increase in color and alkalinity of the source water, no clear correlation dependence of the dose and purification efficiency on these parameters is observed.

Key words

settling , turbidity , chromaticity , coagulation , flocculation , natural water , ferric sulfate , alkalinity , hydrolysis , ferric chloride