AWWA WQTC69501

This powerpoint presentation begins by providing a brief overview of two sampling campaigns to evaluate leadconcentrations in Montreal's tap water. Study objectives included the following:characterize the occurrence and source ofparticulate lead in Montreal tap water;stimulate lead particle detachment;investigate the bioavailability of leadparticles;analyze the composition of lead particlesand scales;determine parameters affecting dissolvedand particulate lead concentrations; and,compare random daytime (RDT) sampling vssampling with 30 minutes of stagnation. Materials and methods for thesampling protocol included the following: 2007, 45 LSL houses, 3 samples each (plus 3 sub-samplesfor determination of dissolved Pb); and, PSS, 9 LSL houses, 3 extra samples after 5min (plus 3 sub-samples for determination of dissolved Pb). Materials and methods for scale deposit analysis included the following: Tof-Sims andLaser Raman Microscopy methods;six Montreal lead pipes wereanalyzed;particle analysis - Tof-Sims (noneed for standards); and,ten typical particles analyzed. Presentation conclusions: the impact of sampling approach on the detection of Pb particulates indicated thatsampling after stagnation is useful to identify the source;however, if flushing is conducted prior to stagnation, it mayeliminate particles accumulated in LSL and premise plumbing;random daytime sampling has been shown to estimateexposure; however, it does not systematically eliminate theoccurrence of particles in the LSL and premise plumbing; itmay produce a better estimate of Pb particulate exposure;creating hydraulic disturbances by varying flow ratesat the tap increases considerably the detachment ofparticulate metals (as observed by van Den Hoven, 2006); creating hydraulic disturbances by varying flow ratesat the tap increases considerably the detachment ofparticulate metals (as observed by van Den Hoven, 2006); two dominant sources of particulate lead werepremise plumbing corrosion in 1st liter (brass, solder), andadsorption of lead from LSL on iron oxide particlesfrom the distribution system and other "foreign"particles (Schock, 1989, Hulsmann, 1990), and morecorrosive conditions (Cl2, dissolved iron), mainly inthe 2nd liter and the liter after 5 min;this hypothesis is confirmed by scale deposit andparticle analysis; and,data analysis showed that lead spikes occurredsimultaneously with tin, copper or zinc spikes. Conclusion for Montreal:presence of background particulate lead could beassociated with more corrosive conditions and thepresence of iron;dissolved iron/higher Cl2 residuals;adsorption of lead from LSL on iron or "foreign" particlesexists, and occurrence of low particulate Pbconcentrations (2L, 5min); and,high particulate lead concentration occurs sporadicallydue to corrosion and detachment of brass and solder. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

32

File Size:

1 file , 1.4 MB