Water Environment Federation (WEF)

Security Aspects of the Free Chlorine Vs Monochloramine Debate for Disinfection by Product Control

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Courtesy of Courtesy of Water Environment Federation (WEF)


In recent years, there has been a move away from the utilization of free chlorine to maintain a residual level of disinfectant in the distribution system towards the use of monochloramine. The reason behind this change is to decrease the formation of disinfection byproducts (DBPs), which are created when the free chlorine reacts with organic material in the water. The use of monochloramines has been deemed to be an inexpensive and effective means to meet new stringent EPA limits for DBPs in drinking water. There are a number of well-known advantages and disadvantages entailed in using monochloramines for this purpose. The fact that many municipalities have made or are making the switch indicates that, to date, the advantages have outweighed the disadvantages. One area of potential concern that has been overlooked in the past dialogue weighing the pros and cons of switching has been the security repercussions
entailed in a switch from free chlorine to monochloramine. That our systems, as they are currently configured, are vulnerable to attack has been widely recognized. While most supply sources are limited in their vulnerability due
to the massive volumes of water involved, the distribution system remains a vulnerable and tempting target as was clearly stated in a recent GAO report to Congress that listed the vulnerability of the distribution system to attack as the largest security risk to water supplies. Terrorists could compromise a system through an assault anywhere in the distribution system through the introduction of any one of a large number of possible threat agents through a backflow event. Due to the threat posed to our water supplies by a potential terrorist attack, it behooves us to look at factors that affect our water quality, such as the switching form free chlorine to monochloramine for disinfectant purposes, in a new light. There are several characteristics of monochloramines that may lead to significant security considerations when it is used to replace free chlorine in the distribution system.

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