What is Water Softening?

Water Softening is the process of removing the dissolved calcium and magnesium salts that cause hardness in water. Unlike hard water, softened water will not form insoluble scale or precipitates in pipes and tanks or interfere with cleaners such as soap. Water softening is thus indispensable in many industries, and small water-softening units are used in homes in many countries.

Thus, It is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions. Soft water also extends the lifetime of plumbing by reducing or eliminating scale build-up in pipes and fittings. Water softening is usually achieved using lime softening or ion-exchange resins but is increasingly being accomplished using nanofiltration or reverse osmosis membranes.

The following equilibrium reaction describes the dissolving/formation of calcium carbonate scales:

CaCO3 + CO2 + H2O = Ca2+ + 2HCO3

Ion Exchange Process

Calcium and magnesium ions can be easily removed by the ion exchange process. Unlike hard water, softened water will not form insoluble scale or precipitates in pipes and tanks or interfere with cleaners such as soap. Water softening is thus indispensable in many industries, and small water-softening units are used in homes in several countries.
Hard water can be problematic because the calcium and magnesium ions react with the higher fatty acids of soap to form an insoluble gelatinous curd, thereby causing a waste of the soap. In boilers, the calcium and magnesium in hard waters form a hard adherent scale on the plates. As a result of the poor heat conductivity of the scale, fuel consumption is increased, and the boiler deteriorates rapidly through the external overheating of the plates. Sodium carbonate, if present, hydrolyzes to produce free alkali that causes caustic embrittlement and failure of the boilerplates.

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