Chemical Technology January 2015

Water production, technical issues and economics by Perialwar (Regu) Regunathan

Can calcium and magnesium (‘hardness’) in drinking-water contribute to preventing disease? Typical diets are often deficient in calcium and magnesium, both essential for strong bones and teeth, and for cardiovascular function. There is also evidence that ‘hard’ drinking-water may be associated with reduced risks for some diseases.

Central softening The issue of having calcium and magnesium in finished drinking-water can be of importance not only for those water suppliers that utilise desalination processes, but also for the broader water industry internationally. The Global Water Research Coalition, as representative of many water-related research institutes worldwide, has prepared a review on the reasons and criteria for softening and conditioning (Mons et al 2007). It recommends that in addition to nutrition, other health-related and other pertinent aspects should be considered. Both very soft and very hard water can interact with piping materials, whichmay negatively impact the water quality and the integrity of the piping system. It is therefore important that those other considerations, including the optimal composition of piped drinking-water to prevent corrosion and scaling, are taken into account.

In several countries, softening is sometimes applied centrally (eg, Netherlands, Germany, Belgium, France, United States). Point-of-entry (POE) softening at the indi- vidual residence is the most frequently applied method of softening. Central softening of drinking-water offers public health and environmental benefits. Moreover, consumer comfort is increased, and there are also several financial benefits for the consumer. Reasons for central softening include: • reduced exposure to trace metals due to reduced corrosion of plumbing in the distribution system and household plumbing; • reduced costs because of reduced consumption of detergents and energy as well as lessened need to use private softeners; • fewer discharges to the environment (eg, less detergents,

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Chemical Technology • January 2015