Water Supply Vol 2 No 3 pp 191–198 © IWA Publishing 2002
Factors controlling nitrosamine formation during wastewater chlorination
W.A. Mitch* and D.L. Sedlak**
*Department of Civil and Environmental Engineering, University of California, Berkeley, 609 Davis Hall, Berkeley, California 94720, USA
**Department of Civil and Environmental Engineering, University of California, Berkeley, 609 Davis Hall, Berkeley, California 94720, USA
ABSTRACT
Recent discoveries of the formation of low levels of the potent carcinogen N-nitrosodimethylamine (NDMA) during wastewater chlorination has caused concern where indirect potable water reuse is practiced. Experiments indicate that nitrosamine formation during chlorination of wastewater is consistent with a reaction scheme involving the slow formation of a hydrazine intermediate from a secondary amine and monochloramine, followed by its rapid oxidation to the corresponding N-nitrosamine. A survey of precursors indicates that secondary amines form their corresponding N-nitrosamines to the greatest extent. However, molecules containing the secondary amine as a functional group can also form the corresponding N-nitrosamine. NDMA is the predominant N-nitrosamine found in chlorinated wastewater. However, other nitrosamines are detected. These N-nitrosamines may be important if the summed risk posed by the exposure to all N-nitrosamines is considered.
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