Raw water is natural water found in the environment, such as rainwater, ground water, and water from bodies like lakes and rivers. Water in this form is considered raw, as opposed to water which has been treated before consumption, such as drinking water or water which has been used in an industrial process, such as waste water. Millions of people in developing countries rely on untreated raw water for their water supply, sometimes purifying it by boiling.
The composition of raw water is naturally variable but commonly contains one or more of the following significant contaminants in the form of dissolved ions, particles and living organisms:
- Humic acid and other complex acids resulting from plant decay. These occur in peat and soil and are significant in discolouring the water.
- Minerals which make water hard. Most common are carbonates of calcium and magnesium.
- Particles of clay and silt.
- Microorganisms such as bacteria, viruses, protozoa and their cysts.
- Dissolved air molecules, especially oxygen
- Salt, which makes water brackish, having more salinity than fresh water, but not as much as seawater.
- Huq, A et al. (July 1996). "A simple filtration method to remove plankton-associated Vibrio cholerae in raw water supplies in developing countries". Vol. 62, No. 7. Applied and Environmental Microbiology. pp. 2508–2512. Retrieved June 7, 2012.
- Safe Drinking Water Committee (1980), "Raw water quality", Drinking Water and Health 2, National Academies, pp. 7 et seq.
- Clark, J. A. et al. (1982). "Characterization of indicator bacteria in municipal raw water, drinking water, and new main water samples". 28 (9). Canadian Journal of Microbiology. pp. 1002–1013. Retrieved June 6, 2012.
- LeChevallier, M W: et al. (November 1980). "Enumeration and characterization of standard plate count bacteria in chlorinated and raw water supplies". Vol. 40, No. 5. Applied and Environmental Microbiology. pp. 922–930. Retrieved June 7, 2012.
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