Comparison of stannous chloride and phosphate for lead corrosion control: Fid-Bau Portal

Comparison of stannous chloride and phosphate for lead corrosion control

Hozalski, Raymond M. / Esbri‐Amador, Elizabeth / Chen, Che Fei

Because of health hazards associated with lead toxicity, the U.S. 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 U.S. 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.