Systems utilizing chloramines for residual disinfection often are required to stop
ammonia addition for at least one month per year. This time is utilized to "burn" or
"flush" the system with a high strength disinfectant and is typically accompanied by a
program of hydrant flushing to ensure the chlorinated water travels completely through
the distribution system. A previous study indicated that switching from chloramines
to free chlorine residual disinfectant reduced bacteria levels as measured by heterotrophic
plate count (HPC); the effect was temporary, however, because the levels increased again
upon return to chloramination. To build upon this work, one of the project goals was to
examine the effect of switching from combined to free chlorine and then back to
combined chlorine on bacteria levels in two neighboring distribution systems (DS-1 and
DS-2) with similar raw water quality, and to link these effects to water age and water
quality parameters including disinfectant residual, assimilable organic carbon, and
nitrogen species (nitrate, nitrite, ammonia).
A second project goal involved examining a "dead-end" site in the distribution system for
bacterial growth after periods of unsustained chlorine residuals. Additionally, nitrogen
species were analyzed to examine the possibility of nitrification at the site. Includes 15 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 170 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 7 |
| Published : | 11/01/2007 |
