AWWA WQTC69501

This powerpoint presentation begins by providing a brief overview of two sampling campaigns to evaluate lead concentrations in Montreal's tap water. Study objectives included the following: characterize the occurrence and source of particulate lead in Montreal tap water; stimulate lead particle detachment; investigate the bioavailability of lead particles; analyze the composition of lead particles and scales; determine parameters affecting dissolved and particulate lead concentrations; and, compare random daytime (RDT) sampling vs sampling with 30 minutes of stagnation. Materials and methods for the sampling protocol included the following: 2007, 45 LSL houses, 3 samples each (plus 3 sub-samples for determination of dissolved Pb); and, PSS, 9 LSL houses, 3 extra samples after 5 min (plus 3 sub-samples for determination of dissolved Pb). Materials and methods for scale deposit analysis included the following: Tof-Sims and Laser Raman Microscopy methods; six Montreal lead pipes were analyzed; particle analysis - Tof-Sims (no need for standards); and, ten typical particles analyzed. Presentation conclusions: the impact of sampling approach on the detection of Pb particulates indicated that sampling after stagnation is useful to identify the source; however, if flushing is conducted prior to stagnation, it may eliminate particles accumulated in LSL and premise plumbing; random daytime sampling has been shown to estimate exposure; however, it does not systematically eliminate the occurrence of particles in the LSL and premise plumbing; it may produce a better estimate of Pb particulate exposure; creating hydraulic disturbances by varying flow rates at the tap increases considerably the detachment of particulate metals (as observed by van Den Hoven, 2006); creating hydraulic disturbances by varying flow rates at the tap increases considerably the detachment of particulate metals (as observed by van Den Hoven, 2006); two dominant sources of particulate lead were premise plumbing corrosion in 1st liter (brass, solder), and adsorption of lead from LSL on iron oxide particles from the distribution system and other "foreign" particles (Schock, 1989, Hulsmann, 1990), and more corrosive conditions (Cl2, dissolved iron), mainly in the 2nd liter and the liter after 5 min; this hypothesis is confirmed by scale deposit and particle analysis; and, data analysis showed that lead spikes occurred simultaneously with tin, copper or zinc spikes. Conclusion for Montreal: presence of background particulate lead could be associated with more corrosive conditions and the presence of iron; dissolved iron/higher Cl2 residuals; adsorption of lead from LSL on iron or "foreign" particles exists, and occurrence of low particulate Pb concentrations (2L, 5min); and, high particulate lead concentration occurs sporadically due to corrosion and detachment of brass and solder. Includes tables, figures.