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Comparison of corrosion scales in full and partially replaced lead service lines after changes in water quality
Citation:
Doré, E., M. DeSantis, M. Schock, E. Deshommes, S. Nour, L. Laroche, AND M. Prevost. Comparison of corrosion scales in full and partially replaced lead service lines after changes in water quality. Presented at 17th National Canadian Conference on Drinking Water, Ottawa, ON, CANADA, October 16 - 18, 2016.
Impact/Purpose:
The main objective is to compare scales from full and partial LSLs harvested from the field and from a pilot setup fed with water from the same distribution system and subjected to water quality changes.
Description:
Preliminary results from scales formed 38 weeks following the LSL replacement simulations revealed differences in scale formations amongst varying water qualities and pipe sequence. Rigs fed with dechlorinated tap water show distinct pH gradients between the galvanic and the background zones. Hydrocerussite and litharge are found both in field and pilot rigs. However, plumbonacrite, massicot, scrutinyite and plattnerite are only present in pipes harvested directly from the field. Laurionite, leadhillite, cerussite and calcite are found in rigs from the pilot. Cerussite is mostly present in the galvanic zones, close to the connection to the Cu pipe. Different types of scales are present in the rigs from the pilot and from the field, suggesting that differences in the formation in the scales and therefore differences in lead release from the pipes. The particulate Pb fraction in water samples is more important in samples from the pilot than from the field, median concentrations are 85X higher in partial LSL and 10X higher in full LSL in the pilot. Lead phosphates are present in the scales from the rigs treated with orthophosphate. Complete results will be obtained by the end of July 2016.
