Effects and Trends of Chloramine in Your Drinking Water...

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Chloramines refer to three compounds: mono-di and tri-chloramine.  The most common and effective chloramine used as a disinfectant is monochloramine, an inorganic compound with the the formula NH2Cl.  It has been used by water utilities since 1918(Denver, CO).  Chloramine use is closely regulated and the current US EPA maximum contaminant lever (MCL) is four mg/L (or ppm).  Since chloramine is not commercially available, it must be generated onsite by adding ammonia to drinking water containing chlorine.  Because chloramine is a weaker disinfectant compared to free chlorine, it is chemically more stable and remains more effective in the distribution system over a longer period of time. 

The choice of chlorine versus chloramine as a secondary disinfectant varies among water utilities based upon their needs.  US EPA does not require water utilities to use chloramines, but a state agency or other authority typically has requirements as to which disinfectant should be used.  Use of chloramines as a secondary disinfectant has been increasing.  

Using chloramine has some other disadvantages as well, including lead release from metal corrosion, biofilms and nitrification.  According to US EPA, chloraminated water is safe to use for drinking, cooking, bathing and other household uses.  People with weak immune systems, including transplant patients and people with AIDS, should not drink chloraminated water.  Chloramine must be removed prior to use in kidney dialysis machines.