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Because of health hazards associated with lead toxicity, theUS Environmental Protection Agency in 1991 promulgated theLead and Copper Rule (LCR), which established an action levelfor lead at 15 g/L as Pb. Even though lead pipes are no longerinstalled in US distribution systems, many cities still have leadservice connections that can release lead into the water. Tohelp control lead concentrations, many water utilities addcorrosion inhibitors to the treated water to create a protectivescale layer on pipe walls.In this research, a 13-month study investigated the effects ofcorrosion control chemicals on lead release and bacterial growthin a pipe-loop system of new ductile-iron and lead pipes. The fiveparallel lines in the study consisted of a control loop plus fourloops testing orthophosphate, polyphosphate, anorthophosphate-polyphosphate blend, and stannous chloride.Total lead concentrations in the treated loops were significantlylower than in the untreated control, with orthophosphate yielding thelowest lead concentrations of all of the chemicals tested. However,none of the chemicals consistently maintained lead concentrationsbelow the 15-g/L action level for the 8-hour stagnation time sample.The microbiological results suggest that utilities should exercisecaution when adding corrosion control chemicals in order to ensurethat reduced corrosion is not achieved at the expense of other waterquality indicators. For utilities concerned about phosphate's effectson microbiological water quality, stannous chloride may represent aviable option to help them achieve LCR compliance. Includes 32 references, tables, figures.

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Edition: Vol. 97 - No. 3 Published: 03/01/2005 Number of Pages: 15File Size: 1 file , 410 KB