Alkalinity of Drinking Water Explained Page 2
Highly mineralized alkaline waters also cause excessive drying of the skin due to the fact that they tend to remove normal skin oils.
Troublesome amounts of alkalinity can be removed by reverse osmosis technology, along with other total dissolved solids. Other methods of water treatment also remove total dissolved solids, but they are somewhat less suitable for household use compared to reverse osmosis. These methods are distillation and deionization (demineralization). Distillation and deionization equipment are quite expensive and use large amount of space; whereas reverse osmosis water filtration systems could be installed undersink in kitchen or even on countertops.
Several other methods of water treatment will remove alkalinity, but these methods are not satisfactory for household use. These include:
1. Lime softening removes hardness. At the same time, this process will precipitate an equivalent amount of alkalinity. Lime softening is usually restricted to industrial and municipal installations.
Lime softening. While reducing total alkalinity, lime softening does convert HC03– to CO3--, a stronger alkalinity ion.
2. An anion resin regenerated with sodium chloride removes substantially all the anions (carbonates, bicarbonates, and sulfates, as well as nitrates). It replaces these anions with a chemically equivalent amount of chloride ions. The disadvantage of this process is that in almost all cases, it results in a high chloride ion concentration. At the point of exhaustion, the resin has the tendency to unload high concentrations of the anions it carries including the nitrates. For household purposes, such results are almost as undesirable as the original alkalinity.
3. The feed of a mineral acid will neutralize the alkalinity of water. Hydrochloric acid, sulfuric acid or a combination of these can be used. This process converts the bicarbonates and carbonates present into carbonic acid. At this point, it is advisable to provide some method to permit the resulting carbon dioxide gas to escape into the atmosphere. The disadvantages of this acid feed technique are obvious. It is important to have precise control of the process and caution in handling the strong acid.
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