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Chlorine is chlorine is chlorine

All forms of chlorine used for drinking water disinfection (whether gas, on site generation, sodium hypochlorite, calcium hypochlorite, etc.) result in two main chemical fractions--the more active hypochlorous acid ion (HOCl-) and the less active hypochlorite ion (ClO-). It is important to note that hypochlorous acid ion is the most effective disinfectant of all the chlorine residual fractions. This simply is due to the relative ease by which the hypochlorous acid ion can penetrate bacteria cell walls. In other words, of all chlorine fractions, nothing kills bacteria better and quicker than the hypochlorous acid ion. In order to produce the greatest proportion of hypochlorous acid ion in drinking water supplies, it is necessary to take a very close look at pH effects on each main fraction.

Clearly seen, lowering finished pH raises active hypochlorous acid ion levels. Is it no wonder that systems running at higher pH’s vie for chlorine disinfection alternatives (ozone, chlorine dioxide, chloramines, UV, etc.). Would it not be better, much cheaper, and far less labor intensive to simply lower finished water pH to 6.5-7.0 maximizing hypochlorous acid ion concentration...given appropriate corrosion control can be maintained? Of course it would.