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Lead in Drinking Water: Research Update, Sampling Tools - Canada
Citation:
Lytle, D., M. Schock, AND K. Cahalan. Lead in Drinking Water: Research Update, Sampling Tools - Canada. WQTC, Toronto, Ontario, CANADA, November 11 - 15, 2018.
Impact/Purpose:
Tap water sampling approaches include: Regulatory/Compliance/Treatment Sampling, Exposure Assessment Sampling, Sampling for Lead Sources, No single universally applicable sampling approach for lead in drinking water exists, and There are many protocols, but each has a specific use answering one of those many questions. Sampling for Lead Sources?Where is the lead coming from? Sequential Sampling, Correspond high Pb and/or Zn, Cu, Sn, Fe samples to plumbing volumes, LSL Sampling Option 1: Fully flushed (+short stagnation, 15-30 minutes) samples above ~3 µg/L can indicate a LSL is present (threshold depends on LSL length). Option 2: Allow water to sit motionless in the LSL for at least 6 hours, flush premise plumbing volume to sample LSL stagnation contribution (1 L sample), 3T’s, and 250 mL sample above 20 ppb after overnight stagnation indicates faucet or bubbler likely contributes lead (brass). *250 mL is ~4 ft of plumbing at ½ inch ID (inside diameter). Different sampling approaches address different questions. Sequential sampling is a valuable assessment tool: Identify lead sources Compare relative contributions of lead sources Evaluate long-term effectiveness of CC treatment (soluble and particulate) Evaluate the benefits of LSL removal Sequential sampling can be expensive and complicated, and depends on homeowner not using the water.
Description:
Sequential Sampling: Series of samples taken after stagnation, First samples typically 125-250 mL, Later samples 1 L (uniform plumbing), Correlate sample volumes to plumbing sections, Useful for identifying lead sources and remedial actions-flushing & plumbing replacements. Captures lead peaks from LSL or other plumbing that a 1 L sample may miss, Requires a large number of samples- time and cost intensive, and More complicated to produce an Action Level or interpretation standard.