Why Are So Many People Talking About Monochloramine?

Written by: Hilary Nardone, Lead Environmental Group Manager

The Centers for Disease Control and Prevention and the National Academy of Engineering named water treatment as “one of the most significant public health advancements of the 20th century.” Addition of disinfectants to drinking water has significantly reduced likelihood of disease. Monochloramine is one disinfectant commonly used in drinking water and is formed when ammonia is added to free chlorine.2

Is the use of monochloramine a new approach to disinfection?

Monochloramine has been used as a drinking water disinfectant in the U.S. for over 100 years! It was first used in water treatment in the mid-1910s; the City of Ottawa first used chloramines in 1915. Denver, Colorado, started using monochloramine around the same time as a way to control organisms in the distribution system.Springfield, Illinois and Lansing, Michigan were among the first cities to use this disinfectant in their drinking water in 1929. Many major U.S cities now use monochloramine, including Philadelphia, San Francisco, and Washington, D.C.It is estimated that 30 percent of the U.S’s large water systems currently use monochloramine at some point in their systems, serving 100 million U.S. customers.4

What is new about monochloramine?

A comprehensive before and after study was conducted by the CDC when San Francisco shifted from disinfecting their water supply with chlorine to monochloramine in 2004. The study “demonstrated that Legionella colonization in a plumbing system was effectively eliminated by monochloramine. Hospitals or other facilities colonized with Legionella species might control Legionella growth and prevent disease transmission by adding monochloramine to their potable water system.”6

In a 2016 technology review, the Environmental Protection Agency wrote that studies “support maintaining a chloramine residual in the premise plumbing system in the range of 1 to 2 mg/L as an effective means for containing biofilm growth, minimizing Legionella colonization and preventing outbreaks.”7

Barclay Water Management, Inc. has been hard at work developing a facility-scale building water supplemental monochloramine feed system. Barclay’s iChlor® Monochloramine System permits the continuous supplemental disinfection of potable water supplies in hospitals, nursing care facilities, hotels, and other facilities. Monochloramine is emerging as an integral part of controlling the growth of Legionella bacteria.


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