AWWA WQTC52939

The biostability and microbiological quality in the full-scale chloraminateddrinking water distribution system of the City of St. Paul, Minnesota, wereevaluated. Results from full-scale monitoring demonstrated that the water in thesystem was biologically stable and that there was no significant microbialactivity in the system despite a moderate assimilable organic carbon (AOC)concentration. The excellent biostability and microbiological quality of thesystem could be attributed to a combination of factors including the use ofmonochloramine as terminal disinfectant, high residual chlorine in the system,and low water temperature for much of the year. A batch experiment was conductedto examine the importance of a disinfectant residual to maintaining thebiostability and microbiological quality of the system. Includes 12 references, figures.