Bicarbonate is the principal alkaline form in natural (untreated) water, although carbonate and hydroxide are found in lime or lime-soda treated waters, and phosphates and silicates may also contribute to alkalinity in waste-waters. Adverse effects of high alkalinity in boiler feed-water include corrosion from liberated carbon dioxide and foaming—with resultant carry-over of contaminants. Scaling can also occur in cooling water systems due to the formation of insoluble calcium carbonate. For drinking water, the U.S. Public Health Service Standards limit alkalinity to 35 ppm over the hardness level.

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