Because of health hazards associated with lead toxicity, the
US Environmental Protection Agency in 1991 promulgated the
Lead and Copper Rule (LCR), which established an action level
for lead at 15 µg/L as Pb. Even though lead pipes are no longer
installed in US distribution systems, many cities still have lead
service connections that can release lead into the water. To
help control lead concentrations, many water utilities add
corrosion inhibitors to the treated water to create a protective
scale layer on pipe walls.
In this research, a 13-month study investigated the effects of
corrosion control chemicals on lead release and bacterial growth
in a pipe-loop system of new ductile-iron and lead pipes. The five
parallel lines in the study consisted of a control loop plus four
loops testing orthophosphate, polyphosphate, an
orthophosphate-polyphosphate blend, and stannous chloride.
Total lead concentrations in the treated loops were significantly
lower than in the untreated control, with orthophosphate yielding the
lowest lead concentrations of all of the chemicals tested. However,
none of the chemicals consistently maintained lead concentrations
below the 15-µg/L action level for the 8-hour stagnation time sample.
The microbiological results suggest that utilities should exercise
caution when adding corrosion control chemicals in order to ensure
that reduced corrosion is not achieved at the expense of other water
quality indicators. For utilities concerned about phosphate's effects
on microbiological water quality, stannous chloride may represent a
viable option to help them achieve LCR compliance. Includes 32 references, tables, figures.
| Edition : | Vol. 97 - No. 3 |
| File Size : | 1
file
, 410 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 15 |
| Published : | 03/01/2005 |
