Ordinary tap water contains a variety of impurities, including dissolved organics, inorganics, and gases; suspended particles; numerous microorganisms; and pyrogens, or endotoxins--the byproducts of bacterial degredation. Although the actual types and amounts of contaminants often vary with geographic location, seasonal cycles, and other factors, they are all considered by researchers to be detrimental to life-sciences investigations and must be eliminated.
Six basic water-purification technologies--distillation, ion exchange, carbon adsorption, reverse osmosis, microporous membrane filtration, and ultrafiltration--represent the standard methods for removing impurities. However, because some of these procedures tend to remove only a single type of contaminant, an effective water purification system should consist of a combination of techniques to achieve the desired water quality, industry experts recommend.
"If you look at the bulk flow of water, starting with tap water coming into the laboratory, about 90 to 99 percent of the particles, dissolved ions, organics, and bacteria should be removed...
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