Chemical Technology January 2015

systemwith an activated carbon filter can also yield drinking- water virtually free of many organic and inorganic chemi- cals of potential concern. In addition to removing calcium, magnesium and also fluoride, the membrane barrier can reduce many inorganic and particulate contaminants to near detection limits, such as arsenic, perchlorate, lead, copper, radium-226/228, selenium, chromium, turbidity, barium, cadmium, protozoan cysts, TDS, nitrate/nitrite, sodium and sulfate. Similarly, a POU distiller can remove virtually all inorganic chemicals, including calcium and magnesium, along with volatile and non-volatile organics. Volatile organics can be reduced by these devices with a good venting system or by a carbon filter at the outlet of the product water. A POE softener is generally considered as an aesthetic device removing hardness ions, but it can also remove other divalent cations from drinking-waters. While some soften- ers are also certified for their ability to remove barium and radium-226/228, they can also remove copper, cadmium, iron, manganese and other trace-level divalent cations. The balancing of the potential beneficial aspects of these devices against the potential harm of reducing the calcium and/or magnesium and fluoride levels to below the recommended thresholds in drinking-waters is worthy of consideration. Acceptance of the ‘hard water–cardiovas- cular disease benefits’ hypothesis by health experts can lead to several different actions by segments of the water industry as a whole. Some will need to take strong actions, while others may have a set of options: • Utilities with demineralised waters might be guided to add recommended levels of calcium and magnesium. • Cities with naturally ‘soft’ water supplies may face a

expert meeting (WHO 2005) were reviewed by the United States and European home water industry with general concerns and questions due to the potential effects of these recommendations on this industry and its current operations in the marketplace. Each of the industry groups responded separately to the expert group’s recommenda- tions with its own questions and concerns. One important point raised by the POU/POE industry was the difference between naturally soft or low total dis- solved solids (TDS) waters and softened waters. Many of the epidemiological studies have compared health outcomes of consuming naturally soft versus hard waters. However, no known study has compared consumption of hard waters ver- sus softened waters. There are significant composition dif- ferences between naturally soft waters and softened waters. Another point pertained to possible benefits of the con- current removal of some regulated contaminants by POU/ POE treatment methods. Those contaminants are present only in trace levels in drinking-waters supplied by the utili- ties, as the utilities need to reduce them below Maximum Contaminant Levels or MaximumAllowable Limits stipulated by the different countries. However, the levels of these contaminants are usually not at zero, partly because such an extent of reduction in all the treated waters is usually too expensive. Use of certified devices in reducing these contaminants from only the water that is ingested (ie, drinking-water at the household tap) can possibly further reduce risks in some cases (principally for “non-threshold chemicals”). A POU reverse osmosis membrane system removes almost all the calcium and magnesium in source waters. If properly maintained, a POU reverse osmosis membrane

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Chemical Technology • January 2015