8.3 Overview of chemical treatment processes

In the production of drinking water, a number of different chemicals may be added to the water. The types and quantities of chemicals can vary widely and will depend on a range of factors including raw water quality, treatment processes employed and treated water quality objectives. Chemical treatment processes are used to:

• control algae;

• remove colour;

• remove microorganisms;

• remove algal metabolites and synthetic pollutants;

• reduce organic matter;

• reduce the concentration of iron, manganese and other elements;

• reduce pesticides and herbicides;

• control taste and odour;

• soften;

• buffer or modify the pH;

• disinfect;

• control corrosion in distribution systems.

Chemical treatments may also be used for other public health measures, including fluoridation (to prevent dental caries).

The following sections outline common processes employed in water treatment to achieve these objectives.