Selection of most efficient chemicals for water treatment

Summary

The Saratovskoe water reservoir has been the main water source of the Samara public water supply. The municipal water treatment facilities have been built after typical projects and designed for clarification and disinfection of moderately polluted water. Lately sharp suspended solids reduction and organic pollution increase (mainly of natural origin) in the water source have been observed. During flood periods technogenic pollution (surfactants) is present, the concentration of manganese increases, phenol is found. At low water temperature, high color and permanganate value higher doses of chlorine and coagulant are required. Coagulation at low temperatures is inhibited which results in the concentration of residual aluminium and permanganate value exceeding the maximum permissible levels. Higher chlorine dosages cause higher concentrations of chloroorganics in water. Therefore a chemical for using during flood periods that will provide for the required quality of water shall be selected. The results of the laboratory studies of selecting the chemical type and optimum dosage for water purification from the Saratovskoe water reservoir during flood periods are presented. Eighteen coagulant trademarks manufactured by domestic and foreign producers were investigated. The optimum dosages of coagulant and flocculant were defined. From the coagulant samples presented two were selected that could provide for the maximum drinking water clarification at minimum levels of residual aluminium and permanganate value. The final choice can be made on the basis of the technical and economic calculations taking into account the chemical price, delivery cost and required water quality.

Key words

turbidity , sedimentation tank , chromaticity , coagulant , flocculant , filtration , water treatment , residual aluminium , permanganate oxidizability