AWWA JAW57218

A significant concern associated with chloramination is nitrification caused by the growth ofammonia-oxidizing bacteria (AOB) in the distribution system. To prevent nitrification, anymeasures designed to slow the decay of chloramine and its associated release of ammoniashould theoretically reduce the occurrence of AOB growth. Pilot-scale studies were used toevaluate whether enhanced removal of natural organic matter and pH adjustment delayed theonset of nitrification. For the system described in this article, nitrification occurred at pHvalues ranging from 7.9 to 8.9, with the time to onset of nitrification being fastest at about pH8.5. However, pretreatment with enhanced coagulation successfully delayed the onset ofnitrification compared with pretreatment with conventional coagulation. Nitrification did notoccur when total chlorine concentrations were 2.2 mg/L as Cl2 or more. Similarly, nitrificationdid not occur in locations with biocide-to-food ratios of 1.9 mg Cl2/mg N or more. Includes 19 references, tables, figures.

Product Details

Edition:

Vol. 94 - No. 11

Published:

11/01/2002

Number of Pages:

12

File Size:

1 file , 310 KB