Ma, Yi Hua Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts.
Last reviewed:February 2020
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- Lime-soda processes
- Ion-exchange softening
- Zeolite process
- Ion-exchange resins
- Reverse osmosis
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The process of removing divalent cations, usually calcium (Ca2+) or magnesium (Mg2+), from water. Water containing more than 120 mg of these ions per liter, expressed in terms of calcium carbonate (CaCO3), is generally classified as a hard water. Hard waters are frequently unsuitable for many industrial and domestic purposes because of their soap-destroying power and tendency to form solid deposits of calcium carbonate (scale) in equipment such as boilers, pipes, and engine jackets. Therefore it is necessary to treat the water either to remove or to alter the constituents for it to be fit for the proposed use.
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