The goal of disinfection of public water supplies is to eliminate pathogens that cause water-borne diseases. In addition to potential pathogens, raw water may also contain pollutants that may interfere with the disinfection process. These pollutants include inorganic and organic molecules, particles, and other organisms, such as invertebrates.
Disinfection of drinking water is to prevent the occurrence of intestinal infectious diseases. Commonly used disinfection methods are the addition of liquid chloride, sodium hypochlorite. Chlorination not only helps prevent spread of Escherichia coli infections, it can also destroy bacteria, algae and mold that may grow on the walls of the water storage system.
Poly aluminium chloride PAC is the common used coagulant in drinking water treatment, which can make flocs form and settle quickly, and the formed flocs are easy to filter.
The direct indicator to evaluate the disinfection effect of tap water is the total number of bacteria, the total coliform group, and the indirect indicator is turbidity and residual chlorine.