AWWA WQTC65946

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 (Cl₂:NH₃) 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 (NHCl₂), 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 Cl₂:NH₃ 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.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

7

File Size:

1 file , 170 KB