Many drinking water utilities replace free chlorine with chloramines (primarily
monochloramine) for secondary disinfection in order to reduce the formation of
chlorinated disinfection byproducts (DBPs) within the distribution system. Because
monochloramine is a weaker oxidant than free chlorine, many water utilities that employ
chloramination temporarily switch to free chlorine in an attempt to control bacterial
regrowth and, in particular, nitrification in distribution systems. The objective of this
research was to assess the water quality impacts of temporary switches to free chlorine
for one month periods within the distribution systems of two water utilities. Results to
date have indicated several important effects: a traveling front of the breakpoint
chlorine chemistry with very low total chlorine residual occurs within the distribution
system following the switch from chloramines to free chlorine and again when free
chlorine replaced chloramines; DBPs increase within the distribution system during
the free chlorination periods although the extent varies both spatially and temporally;
bacteria continue to remain attached to pipe surfaces after periods of free chlorination;
bacteria on pipe walls as measured by heterotrophic plate counts (HPC) is not
reduced during exposure to free chlorine; and, nitrifying bacteria have been identified on
pipe surfaces even though there was very little evidence of nitrification as measured by
an increase in nitrate concentration the bulk water of the system. Includes 31 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.4 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 17 |
| Published : | 06/17/2005 |
