When iron and manganese are oxidized, they become insoluble in water and can then be removed by sedimentation and filtration. Potassium permanganate is also used to oxidize the organic contaminants that cause taste and odor problems. In the past, chlorine was used for these problems as well as for iron and manganese control. However, research has shown that chlorine plus organic material can intensify some unpleasant tastes and odors and can produce chlorination by-products such as trihalomethanes. By using potassium permanganate instead of chlorine for pre-treatment, chlorine can be added later in the treatment process and used only for disinfection.
Consumers thus receive a healthier and more aesthetically pleasing drinking water.
In water treatment, alum is used as a coagulant. A coagulant binds together very fine suspended particles into larger particles that can be removed by settling and filtration. It is an alkaline compound that is added to the water for pH adjustment. Since filter alum is an acidic salt, it lowers the pH of the water, and lime is used to neutralize this effect. Chlorine destroys pathogenic microorganisms, oxidizes undesirable elements such as iron and manganese and reduces some tastes and odors.