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Municipal Purification of Water

9

9.1 The Need for Water Purification

Water is a basic necessity of life and, as has been seen
in the previous chapter, many diseases can easily be
transmitted through it. The purification of water is the
removal from raw waters, undesirable materials,
whether biological or chemical in nature, so as to pro-

duce water that is fit for human consumption and for

other uses. Substances that are removed during water

purification include bacteria, viruses, algae, fungi, par-

asites (such as Giardia or Cryptosporidium), minerals

(including toxic metals such as lead, copper, etc.), and

man-made chemical pollutants. Some of the materials

removed are detrimental to health, whereas others do

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 purifi-

cation include the following: pretreatment (pre-coagulation, pre-disinfection),

aeration, coagulation, filtration (slow, rapid, ultrafiltration, carbon filtration), dis-

infection (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 gov-

ernmental 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.

Keywords

Water purification • Fecal indicators • Microbiological & chemical standards of

drinking water • Standards for recreational waters • Shell fish growing waters

• USA EPA, EU EEA, and WHO water standards • UV, reverse osmosis,
  plumbosolvency

N. Okafor, Environmental Microbiology of Aquatic and Waste Systems,
DOI 10.1007/978-94-007-1460-1_9, © Springer Science+Business Media B.V. 2011