Lead in Drinking Water: Research Update, Sampling Tools

Transcription

1 Lead in Drinking Water: Research Update, Sampling Tools Darren A. Lytle and Michael R. Schock US EPA/ORD/NRMRL/WSWRD Kelly Cahalan ORAU

2 Tap Water Sampling Approaches Regulatory/Compliance/Treatment Sampling Exposure Assessment Sampling Sampling for Lead Sources No single universally applicable sampling approach for lead in drinking water exists There are many protocols, but each has a specific use answering one of those many questions 2

3 Multiple Options Exist for Lead Sampling First Draw Random Daytime Sampling (RDT) Fixed Stagnation Time (30MS) Sampling Purpose -Regulatory (US) -Treatment Assessment -Regulatory (UK) -Treatment Assessment -Regulatory (Ontario) -Treatment Assessment Protocol -6+ hr stagnation -Collect first liter -Random sample collection (variable stagnation times) -Collect first liter -2-5 min. flush -30 min stagnation -Collect first two liters Service Line Sampling (Second Draw) -Regulatory (US) -Lead Source Assessment -6+ hr stagnation -Volume between tap and LSL flushed -Collect 1 L

4 Composite Proportional Sampling Purpose Exposure Assessment Protocol -Normal water use patterns -A device collects 5% of every draw from the tap for consumption -Used for 1 week Particle Stimulation Sampling -Lead Type Assessment -Exposure Assessment -5 min stagnation -Collect first liter and maximum flow rate, open and close tap five times, fill rest of bottle at normal flow rate. -Collect second liter at a normal flow rate -Collect third liter the same way as the first

5 Fully Flushed Sequential Sampling (Profile Sampling) Sampling Purpose -Lead Source Assessment -Treatment Assessment -Lead Source Assessment Protocol -Several piping volumes flushed -Collect first liter -Defined stagnation time -Collect samples of defined volume (125 ml, 250 ml, 1 L, etc.) 3T s Sampling for Schools -Lead Source Assessment -Overnight stagnation -Collect first 250 ml from all taps and fountains -Take follow up sample of overnight stagnation and 30 second flush if first sample> 20 ppb

6 Sampling Considerations 6

7 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, 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 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) 7

8 Plumbing Configuration 8

9 Identifying Pb Sources in a House: Volume as Distance Other pipe branches First 1 L ends here 9

10 Tool: Sample Volumes Represent Source Position in Plumbing Wide-mouth bottles preferable to allow higher flow rate ID = Feet After: Schock, M. R.; Lytle, D. A. Internal Corrosion and Deposition Control; In Water Quality and Treatment: A Handbook of Community Water Supplies; Sixth ed

11 Sample Volume Per Length: Cu Material Type Nominal Size (in) OD (in) Thickness (in) ID (in) ml/ft ml/m ft per L m per L Copper tube K Copper tube L Copper tube M Copper tube K Copper tube L Copper tube M Copper tube K Copper tube L Copper tube M

12 Example: ¾-in ID Type L Copper Material Type Nominal Size (in) OD (in) Thickness (in) ID (in) ml/ft ml/m ft per L m per L Copper tube K Copper tube L Copper tube M Copper tube K Copper tube L Copper tube M Copper tube K Copper tube L Copper tube M

13 Sample Volume/Length (other) 13

14 Sequential Sampling Series of samples taken after stagnation First samples typically 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 More complicated to produce an Action Level or interpretation standard

15 EPA Sequential Sampling Protocol

16 Identification of Lead Contribution and Plumbing Materials (Michigan Case) Elevated iron and lead suggests particles. Plumbing Inspection Lead Lead service line in unknown region likely. Iron 16

17 Impact of Corrosion Control on Lead Reduction over Time (Ohio Case) Lead peak shift possibly because water used during stagnation. 17

18 Impact of Corrosion Control on Lead Reduction over Time (Michigan Case) Increasing Time 18

19 Benefit of Lead Service Line (LSL) Removal (Michigan Case) Before LSL removal Copper elevated after replacing lead. 19

20 Impact of Treatment on Lead Particles (Michigan Case) 20

21 Relative Contribution of Lead Sources (Michigan Case) - 48 homes - Sept ml=~2.5 ft of ½ in diameter pipe

22 Weighted Average Sequential Lead Concentration (WASLC) WWWWWWWWWW = nn ii=1 (CC ii)(vv ii ) nn ii=1 VV ii,where n is the number of sequential samples, C is the lead concentration (µg/l), and V is the sample volume 22

23 Progress of Treatment with Time (Michigan Case) 23

24 Impact of Corrosion Control on Lead Reduction over Time Using WASLC (Ohio Case) 13 or 14 sequential samples. Min., Max., 75th and 25th percentile, and median are plotted. 24

25 Potential Constraints of Sequential Sampling The farther the deviation from plug flow, the less accurate in finding exact location of specific sources The longer the distance of the tap from the source, and the more bends, the more mixing that will take place Lowering peak Pb Loss in resolution May displace precise peak positions relative to source locations Samples can be biased by water passing through leaded devices on the way to the bottle Accurately capturing particulate release highly depends on on-off protocol, flow rate and flow turbulence Count on homeowner to not use water 25

26 Exposure Sampling How do you sample water for lead to reflect what the residents drink? How are customer requested samples collected? Do LCR samples represent exposure? How do lead concentrations in LCR samples compare to other sampling methods?

27 Comparison of Sampling Results 40 June 2016 September 2016 June Lead (µg/l) Cumulative Volume (L) Site 1

28 Comparison of Sampling Results Site 2 Site 3

29 Water Infrastructure for Improvements to the Nation (WIIN) Act Enacted on December 16, 2016 Public Law th Congress An Act To provide for improvements to the rivers and harbors of the United States, to provide for the conservation and development of water and related resources, and for other purposes.

30 SEC Notice to Persons Served (Sec. 2106) This bill amends the Safe Drinking Water Act by requiring public water systems to notify their customers when a lead action level under national drinking water regulations is exceeded in more than 10% of customer taps sampled. An action level is generally a certain contaminant level that triggers a requirement for the public water system to take additional actions to control corrosion. Further, the Environmental Protection Agency (EPA) must: (1) notify customers of an exceedance of the lead action level that has the potential to have serious adverse effects on human health as a result of short-term exposure, if the state or the public water system fails to notify the public within 24 hours after the public water system learns of the violation or exceedance; and (2) issue the notice no later than 24 hours of being notified of the exceedance. Community water systems' consumer confidence reports must include a definition of "action level." The EPA must establish a strategic plan for conducting targeted outreach, education, technical assistance, and risk communication to populations affected by lead in the public water system. EPA employees must forward to the public water system any data indicating that the drinking water of a household served by a public water system contains a level of lead that exceeds the lead action level. Information on the sampling techniques used to obtain the data must also be forwarded with the data. The public water system must then disseminate to affected households information on the exceedance of a lead limit, its potential adverse effects on human health, corrective steps underway, and advice on whether customers should seek alternative water supplies. The EPA must disseminate the information if the public water system or the state fails to do so. The EPA must: (1) make information about lead in drinking water available to the public, and (2) carry out targeted outreach strategies that focus on educating groups that are at greater risk than the general population for adverse health effects from exposure to lead in drinking water.

31 Water Infrastructure Improvements for the Nation (WIIN) Act

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33 Summary 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 33

34 Contact Information Darren A. Lytle Michael Schock Notice The findings and conclusions in this presentation have not been formally disseminated by the U.S. Environmental Protection Agency and should not be construed to represent any Agency determination or policy. Any mention of trade names or commercial products does not constitute endorsement or recommendation for use. 34

35 First Draw Random Daytime Sampling (RDT) Fixed Stagnation Time (30MS) Sampling Purpose -Regulatory (US) -Treatment Assessment -Regulatory (UK) -Treatment Assessment -Regulatory (Ontario) -Treatment Assessment Protocol -6+ hr stagnation -Collect first liter -Random sample collection (variable stagnation times) -Collect first liter -2-5 min. flush -30 min stagnation -Collect first two liters Service Line Sampling (Second Draw) -Regulatory (US) -Lead Source Assessment -6+ hr stagnation -Volume between tap and LSL flushed -Collect 1 L

36 Composite Proportional Sampling Purpose Exposure Assessment Protocol -Normal water use patterns -A device collects 5% of every draw from the tap for consumption -Used for 1 week Particle Stimulation Sampling -Lead Type Assessment -Exposure Assessment -5 min stagnation -Collect first liter and maximum flow rate, open and close tap five times, fill rest of bottle at normal flow rate. -Collect second liter at a normal flow rate -Collect third liter the same way as the first

37 Fully Flushed Sequential Sampling (Profile Sampling) Sampling Purpose -Lead Source Assessment -Treatment Assessment -Lead Source Assessment Protocol -Several piping volumes flushed -Collect first liter -Defined stagnation time -Collect samples of defined volume (125 ml, 250 ml, 1 L, etc.) 3T s Sampling for Schools -Lead Source Assessment -Overnight stagnation -Collect first 250 ml from all taps and fountains -Take follow up sample of overnight stagnation and 30 second flush if first sample> 20 ppb

38 Multiple Options Exist for Lead Sampling First Draw Random Daytime Sampling (RDT) Fixed Stagnation Time (30MS) Fully Flushed Sequential Sampling (Profile Sampling) Sampling Purpose -Regulatory (US) -Treatment Assessment -Regulatory (UK) -Treatment Assessment -Regulatory (Ontario) -Treatment Assessment -Lead Source Assessment -Treatment Assessment Lead Source Assessment Protocol -6+ hr stagnation -Collect first liter -Random sample collection (variable stagnation times) -Collect first liter -2-5 min. flush -30 min stagnation -Collect first two liters -Several piping volumes flushed -Collect first liter -Defined stagnation time -Collect samples of defined volume (125 ml, 250 ml, 1 L, etc.) Composite Proportional Exposure Assessment -Normal water use patterns -A device collects 5% of every draw from the tap for consumption -Used for 1 week Particle Stimulation Sampling Service Line Sampling (Second Draw) 3T s Sampling for Schools -Lead Type Assessment -Exposure Assessment -Regulatory (US) -Lead Source Assessment -Lead Source Assessment -5 min stagnation -Collect first liter and maximum flow rate, open and close tap five times, fill rest of bottle at normal flow rate. -Collect second liter at a normal flow rate -Collect third liter the same way as the first -6+ hr stagnation -Volume between tap and LSL flushed -Collect 1 L -Overnight stagnation -Collect first 250 ml from all taps and fountains -Take follow up sample of overnight stagnation and 30 second flush if first sample> 20 ppb

39 Comparison of Sampling Results 556 W. Ohio LCR Avg Sequential Max Sequential Lead (µg/l) June 2016 September 2016 June 2017 Sample Round