With a change to surface water many municipalities have had episodes of poor water quality that are the result of several factors. This memo is intended to give a little background on why conversion was necessary in the Houston area, a discussion of what those factors are, and recommendations on what to do as we move forward.
Our conversion to surface water in the Houston area is the result of subsidence, but many areas of Texas use surface water because of a lack of ground water. Surface water differs from ground water in many ways but of particular importance is that it has naturally occurring organic material in it. This is important because when disinfected with chlorine, this material forms byproducts that are shown to be carcinogenic. The byproducts are many and generally classified as either haloacetic acids or as trihalomethanes. Collectively they are called disinfection byproducts (DBPs) and are now regulated by the EPA. To avoid the formation of DBPs, many entities supplying surface water changed from using straight chlorine to chloramines, chlorine dioxide, or other disinfectants. Chloramines were the disinfectant of choice in Houston. Making chloramines is a tricky process, and the addition of too much chlorine can form Di- and Trichloramines that have a bad taste and odor. If chlorinated water were blended with chloraminated water the free chlorine residual would combine with the chloramines and form Di- and Trichloramines. This would be undesirable and thus the reason that all the regional water suppliers asked their customers to match their form of disinfection. To read the entire article, please click here.