What does softening refer to in water treatment?

Softening in water treatment specifically refers to the process of reducing the hardness levels of water. Hard water contains high concentrations of minerals, primarily calcium and magnesium ions, which can lead to scale buildup in pipes and appliances and negatively affect the effectiveness of soaps and detergents.

During the softening process, various techniques such as ion exchange are employed to replace these hard minerals with sodium or potassium ions, which do not have the same effects as calcium and magnesium. This results in 'softer' water that is more suitable for residential and industrial applications, as it helps to prevent scale formation and enhances soap efficiency. The reduction in hardness not only improves the longevity of plumbing systems but also contributes to better cleaning outcomes in various uses.

The other options refer to different processes or changes in water quality but do not accurately define softening. For example, adding minerals to improve taste does not pertain to hardness reduction, and increasing alkalinity is unrelated to the softening process, which specifically targets hardness. Filtering impurities pertains to removing particles or contaminants rather than addressing mineral content.