Drinking water is treated to protect public health by removing microorganisms and natural or man-made chemicals that may cause illness in consumers. Water treatment may also be used to improve the water's colour, taste and odour as required.
Protection of water sources from pollution by human or animal waste can reduce the amount of microorganisms entering the water supply, but even water from the most protected wilderness environment may sometimes contain microorganisms capable of causing human disease. Illness can be easily and rapidly transmitted to large numbers of people by contaminated water supplies, therefore it is necessary to treat and/or disinfect water supplies to safeguard against disease. This provides insurance or a barrier against actual or potential contamination.
While some earlier civilisations apparently appreciated the importance of a clean and reliable water supply, the development of scientific understanding of why this was important did not occur until the second half of the 19th century. This was when the nature of infectious disease was first understood and the ability of water supplies to transmit diseases such as cholera and typhoid was first demonstrated.
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The observations of Dr John Snow (1813 - 1858) were important in showing this link between water supply and disease. He began his work during a major cholera outbreak in Britain in 1848 - 49 in which at least 53,000 people died. His systematic investigation of the 1854 outbreak in London showed that cholera death rates were much higher in people consuming water from sewage-polluted regions of the Thames River than in people drinking water from a cleaner part of the river. At that time the germ theory of infectious disease was unknown, and cholera was thought to result from "bad air" or "filthy conditions". John Snow proposed that cholera was transmitted by a "specific poison" (now known to be the bacterium Vibrio cholerae) that could be transmitted from person-to-person or indirectly through contaminated water, food or objects. Dr Snow is best remembered for an incident related to a cholera outbreak in the Golden Square section of London where more than 500 people died within 10 days. He determined that most of the sick people drank water from the Broad Street pump, while residents with a different water supply were not affected. After his findings were reported to the Board of Guardians of the parish, the handle of the pump was removed as a public health measure to prevent people using the water. A memorial to Dr Snow now marks the place where the pump once stood. Dr Snow's findings were published in 1855 in the classic work On the Mode of Communication of Cholera, however it was another 30 years before the germ theory of infectious disease was fully accepted. Link to UCLA site on Dr John Snow http://www.ph.ucla.edu/epi/snow.html
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The approach to the provision of water services that emerged from this 19th century experience was to separate as much as possible the sources of water supply from human habitation and waste disposal. Since complete protection of water sources was often not possible, methods of treating water to kill or remove microorganisms were also developed.
The technologies used to treat water are similar worldwide. There have been a great variety of treatment processes developed and the more important of these are discussed elsewhere in this Guide. The choice of treatment technology depends on the characteristics of the source water, the types of water quality problems likely to be present, and the costs of different treatment systems.
Innovative water treatment technologies are being developed in Australia and overseas with the aim of improving water quality further and reducing the cost of doing so. Much of this Australian research is conducted within the Cooperative Research Centre for Water Quality and Treatment.
Water treatment, together with improved sanitation, has produced great benefits to public health in developed countries by reducing the incidence of many diseases. However, in the developing world, waterborne diseases are still a major cause of illness and death, especially in children. In 2002 the World Health Organisation estimated that over 1.1 billion people (17% of the world's population) lacked access to improved water supplies, and 2.6 billion (42%) lacked basic sanitation facilities. The United Nations General Assembly has proclaimed 2005-2015 as the Water for Life decade, with increased focus on achieving the twin goals of providing safe water and basic sanitation to people in developing countries.
More information can be found on the Water, Sanitation and Health (http:/www.who.int/water_sanitation_health/en/ ) page of the World Health Organisation website.
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Treatment aims to ensure that water is:
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Consumer's Guide to Drinking Water - May 2006 [an error occurred while processing this directive]