2/24/2009 US EPA

WATER SYSTEMS, DISINFECTION BYPRODUCTS, AND THE USE OF

MONOCHLORAMINE

9) How do the kinds and concentrations of disinfection byproducts formed
by monochloramine compare to those formed by chlorine?

Water treated with chlorine and monochloramine contains different types
and concentrations of disinfection byproducts.

•	Compared to chlorine, water treated with monochloramine contains fewer
regulated disinfection byproducts that have been linked to human health
problems.

•	The formation of disinfection byproducts is influenced by source water
type and the type of disinfectant used.

•	Formation can vary daily with the amount of natural organic matter in the
water, temperature, rainfall, and distance from the treatment plant or other
factors influencing water chemistry.1

Compared to chlorine, water treated with monochloramine contains lower
concentrations of regulated disinfection byproducts.2

•	Compared to water treated with chlorine, water treated with
monochloramine contains lower concentrations of the two major types of
regulated disinfection byproducts.2

•	Compared to water treated with chlorine, water treated with
monochloramine contains lower concentrations of regulated disinfection
byproducts linked to bladder cancer.

•	Regardless of the disinfectant used, the types and concentrations of
disinfection byproducts vary from each utility and also from day to day.

Compared to water treated with chlorine, water treated with
monochloramine may contain higher concentrations of unregulated
disinfection byproducts.3

•	EPA scientists are currently studying the unregulated disinfection
byproducts3 that form in water treated with monochloramine.

•	Compared to water treated with chlorine, water treated with
monochloramine may contain different unregulated disinfection byproducts
than chlorinated water.

•	EPA and other organizations continue to conduct research on unregulated
disinfection byproducts.3

Additional Supporting Information:

1.	Water chemistry describes the chemical properties of water such as pH, hardness,
and alkalinity. Changes in water chemistry can cause subsequent changes to the
physical (e.g., taste and odor) and biological (e.g., biofilm formation and nitrification)
properties of water.

2.	TTHM and HAA5 are the regulated disinfection byproduct groups that form at lower
concentrations with monochloramine. See question 7 for more information about TTHM
and HAA5.

3. Examples of these unregulated disinfection byproducts include nitrosamines (including
nitrosodimethylamine, NDMA), iodo-trihalomethanes, and iodo-acids. See question 7 for
additional detail on disinfection byproducts. Specific information on NDMA can be found at
http://www.epa.gov/tio/download/contaminantfocus/epa542f07006.pdf. See question 19 for
additional information on disinfection byproduct research.

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