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Unintentional nitrification occurs in nearly 67% of all utilities practicing chloramination.Nitrification has been linked to distribution systems and storage tanks with long detention times.Excess ammonia during chloramination promotes ammonia-oxidizing bacteria that emit nitriteand form biofilms within distribution systems.Utilities can control nitrification in two ways. First, they can increase the chlorine toammonia molar ratio (Clsub2/sub:NHsub3/sub) to reduce free ammonia in the distribution system. Second, theycan practice breakpoint chlorination to leave a free chlorine residual that hinders biofilm growthand then reapply chloramines downstream. The former strategy increases the formation ofdichloramine (NHClsub2/sub), while the latter forms a series of reactive intermediates. The effect ofboth strategies on the formation of nitrogenous byproducts has not been examined.We conducted experiments to study the impact of Clsub2/sub:NHsub3/sub molar ratios 1 on theformation of three toxic nitrogenous disinfection byproduct families, nitriles (e.g., cyanogenchloride), nitramines (dimethylnitramine) and nitrosamines (e.g., NDMA). For theseexperiments, we used dimethylcyanamide as a model nitrile, dimethylnitramine as a modelnitramine, and NDMA as a model nitrosamine. Includes 5 references, figures.

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Edition: Vol. - No. Published: 11/01/2007 Number of Pages: 7File Size: 1 file , 170 KB