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One third of respondents in a survey of U.S. waterutilities reported using or planning to usechloramines for secondary disinfection, primarily tomaintain a disinfectant residual and minimize formationof disinfection byproducts (DBPs). However,nitrification is a problem in chloraminated systems.Nitrification has been controlled via breakpoint chlorination - periodic switching from chloramines tofree chlorine - but the consequences of this strategyare not well understood. The authors evaluated theeffects of a one-month switch from chloramines tofree chlorine. They concluded that disinfectantswitching alone will terminate nitrification but isunlikely to provide long-term nitrification control.Systems that have used chloramines for a long timeare more likely to have nitrification problems. Cast-ironpipe also might increase nitrification potential.Potential negative effects of disinfectant switchinginclude increased DBP concentrations and periods oflow disinfectant residual. These results can help utilitiesdecide whether or how to use disinfectant switchingas a nitrification control strategy. Includes 38 references, tables, figures.

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Edition: Vol. 100 - No. 10 Published: 10/01/2008 Number of Pages: 12 File Size: 1 file , 910 KB