Municipal Purification of Water

Abstract

Drinking water is a basic necessity for the maintenance of good health in humans, but it is also a vehicle for the introduction of harmful biological agents such as bacterial and protozoan pathogens into the body. Therefore raw waters are purified to render them safe for drinking. The processes adopted in municipal water purification include the following: pretreatment (pre-coagulation, pre-disinfection), aeration, coagulation, filtration (slow, rapid, ultrafiltration, carbon filtration), disinfection (chloramines, ozonation, ultraviolet light, chlorination) miscellaneous treatments (Fe/Mn removal, deionization, reverse osmosis, algal/odor control, softening, ion-exchange, fluoridation, radioactivity removal, plumbosolvency removal). Which of the processes is actually employed depends on the quality of the raw water, the regulations of the appropriate authorities, and the budgetary considerations of the operator. The world over, regulatory authorities decide the maximum contaminants permissible in drinking water and recreational water; thus, the US Environmental Protection Agency (USEPA), the European Union Environmental Agency (EEA), the World Health Organization (WHO), and governmental agencies around the world all set standards, which differ from one another, and which reflect the level of economic, social, and technical expectations and accomplishments of the constituencies to which the standards are addressed.