To comply with disinfection byproduct regulations, many
utilities have chosen to use chloramines rather than chlorine for
residual maintenance in drinking water distribution systems.
However, the switch to chloramines may expose these systems
to another health risk, increased concentrations of lead. This
study investigated total lead release in the presence of free
chlorine and chloramine residuals in drinking waters produced
from ground, surface, desalinated, and blended water sources.
For both desalinated and blended finished waters, more total
lead was released in the presence of chloramines than in the
presence of free chlorine.
Little research has focused on the effect of oxidation-reduction
potentials on metal release. This work verified theoretical
predictions from extensive field data that showed the chloramine
redox potential was lower that the free chlorine redox potential
under equivalent pipe and distribution system environments;
however, the released lead in the lower redox potential chloramine
environment was higher than in the lower redox potential
chlorine environment.
The article relates redox potential to pH and the controlling
solid lead phase for lead release and demonstrates that theoretical
thermodynamic diagrams are practical tools for predicting
release of lead (and perhaps other metals) in distribution systems.
Utility managers who select chloramines for residual maintenance
can use this information to help avoid potential problems of violating
the lead action level. Includes 39 references, tables, figures.
| Edition : | Vol. 98 - No. 2 |
| File Size : | 1
file
, 520 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 11 |
| Published : | 02/01/2006 |
