Lead Tap Sampling Approaches: What Do They Tell You

Transcription

1 Lead Tap Sampling Approaches: What Do They Tell You Michael R. Schock US EPA/ORD/NRMRL/WSWRD Jennifer Tully ORISE Kelly Cahalan ORAU Office of Research and Development

2 Is my water safe to drink? The general public along with many others have asked and will continue to ask this deceptively simple question Many other questions have also been asked such as: What is the general public s exposure to lead in drinking water in this residence/neighborhood/town/distribution system? How effective is the current corrosion control treatment? What forms of lead are present in the drinking water (soluble vs. particulate)? Where is the lead coming from? Does the water meet regulatory standards for lead?

3 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

4 Recent Sampling Questions in Schools Less than 1% of all samples in New York City schools were found to have lead concentrations in excess of EPA guidelines Review of testing found that all samples were collected after pre-stagnation flushing. A practice which may potentially lower lead levels (NYTimes, 8/31/16) Salem and Portland Oregon school sampling Interpretation of the 3T s document that building pipes should be flushed 8-12 hours before sampling. Potential misrepresentation of the actual levels of lead children are exposed to (Statesman Journal, 7/22/16)

5 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

6 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

7 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

8 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

9 Choosing the correct protocol for the question being asked is extremely important Protocol Considerations: Sample volume Number of samples per site Number of sites Stagnation time First draw or flush Site choice Frequency of sampling Sampling Variabilities: Flow Rate Water Temperature Time of Year Pre-flushing Aerator removal Particulate release Accurate Quantification Stagnation time differences

10 Del Toral et al flushing flushing Cartier et al. 2011

11 Regulatory Compliance Sampling Does the water meet regulatory standards? US Lead and Copper Rule (90 th Percentile Action Level 15 ppb) 6+ hour stagnation and 1 L first draw sample Health Canada (90 th Percentile Action Level 15 ppb) 6+ hour stagnation and 1 L first draw sample If more than 10% of the sites exceed 15 ppb, an additional 6+ hour stagnation occurs and four sequential 1 L samples are collected (90 th Percentile Action Level 10 ppb) Ontario (90 th Percentile Action Level 10 ppb) 5 minute flush, 30 MS and two 1 L samples Quebec (Action Level 10 ppb) 5 minute flush and 1 L sample If any sample exceeds 10 ppb, collect another 5 minute flush and 1 L sample plus an additional 4 sequential 1 L samples after 30 MS European Union Drinking Water Directive (Standard 10 ppb) UK: Random Daytime Sampling, 1 L sample

12 1 L, First Draw Sampling (LCR) Long stagnation time, allows sufficient lead amplification May also be used for corrosion control treatment evaluation Low flow rate, aerator removal, and prestagnation flushing have all been used to lower sample concentrations Differences in stagnation times can affect sample concentrations

13 1 L is often short of the volume required to reach the LSL and corresponding lead concentrations Study Del Toral, 2013 Cartier, Laroche, 2011 Premise Plumbing Length LSL Length 3-87 ft ft ft (46 ft) 3-66 ft (23 ft) ft (39 ft) ft (66 ft) PP Volume L (2.3 L) L (1 L) LSL Volume L (1.9 L) L (2.8 L) House Type Location Single Family Pre 1970 Single Family Wartime Single Family Chicago Montreal Montreal Grayman, ft (house total) 200 ft 7 L (house total) 17 L Single Family Cincinnati Hayes, Croft, 2014 Clement, ft ft ft public, ft private 0 (PLSLR), 5-44 ft public, ft private ft (75 ft) L L L L L (12.34 L) Single Family Single Family Single Family Calgary Edmonton France

14 Random Daytime Sampling (RDT) Collect a 1 L sample from a random residence during business hours without further stagnation or flushing Captures a wide range of stagnation times Can gauge average population exposure if enough samples are collected In order to assess treatment effectiveness samples should be collected from different distribution system zones based on water quality RDT is the most variable of all sampling methods, and therefore requires the most samples

15 UK Success with RDT Hayes & Croft 2012 Currently 99.5% compliance with 10 µg/l Orthophosphate dosing has reduced lead concentrations by more than 95% Models conclude RDT is representative Hayes & Croft 2012

16 Exposure Assessment Sampling What is the general public s exposure to lead in drinking water? RDT & 30 Minute Stagnation (MS) Representative of the approximate inter-use stagnation time Requires appropriate number of samples based on population size and variability within water system Composite Sampling Devices Exposure reference method Collects proportion of all lead consumed per week These are the applicable sampling methods to use when a customer asks Is my water safe to drink? *Reminder: LCR sampling does not assess exposure*

17 Side Stream Composite Sampler Collects lead under normal use conditions, capturing a range of flow rates, stagnation times, flow durations, and temperatures Device is affixed to the tap & consumer operated 5% of every draw meant for consumption is routed into holding tank After one week the composite sample analyzed for lead average lead concentration Does not collect all lead Seen as inconvenient and cumbersome by residents van den Hoven, 1987

18 Sampling to determine the contribution of water lead to blood lead levels Studies cited in the 1991 LCR FR used a variety of sampling techniques including: first draw, 30 MS, RDT, fully flushed, and composite to determine exposure Based on the question asked the most informative studies should have focused on exposure sampling techniques such composite or particulate stimulation sampling

19 Water Treatment Assessment Sampling How effective is the current corrosion control treatment? LCR, 30MS, & Fully Flushed Compare samples from same house each year Standardized protocol eliminates variability from water use patterns 30MS best choice RDT Look for overall decrease in lead concentrations system-wide Cannot assess corrosion control treatment at individual houses

20 Sequential Sampling Sampling for Lead Sources Where is the lead coming from? 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)

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22 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 actionsflushing & plumbing replacements Captures lead peaks from LSL or other plumbing that a 1 L sample may miss Requires a large number of samplestime and cost intensive More complicated to produce an Action Level or interpretation standard Courtesy: Kelsey Pieper, UNC

23 In addition to lead, looking at copper, zinc, and iron concentrations can provide useful information Consistent high Cu is interior piping Higher copper with falling lead shows PLSLR High Zn and Cu, associated with rising Pb is the meter area Dropping copper with dropping Zn shows LSL

24 Sampling for Lead Type What forms of lead are present in the drinking water? Particulate Easy to miss with standard sampling protocols High flow rate, hydraulic disturbances, & certain materials (brass especially) spur release Harder to quantify with acidification Soluble ~ µm Sampling Protocol to disturb scale/generate particulate and protocol to filter samples for dissolved lead content Sandvig et al 2008 Lead Pipe Scales Schock et al 2014

25 Summary Different sampling protocols produce different lead concentrations and sample different sources/forms of lead The efficacy of a single protocol varies from building to building due to plumbing differences and other site variabilities Choosing the correct protocol for the sampling purpose is crucial to producing meaningful data

26 Contact Information Michael Schock Jennifer Tully Kelly Cahalan 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.

27 References Cardew, P. T. (2003). "A Method for Assessing the Effect of Water Quality Changes on Plumbosolvency Using Random Daytime Sampling." Water Res 37: Cartier, C., et al. (2011). "Investigating Dissolved Lead at the Tap Using Various Sampling Protocols." Journal - American Water Works Association 103(3): Clark, B., et al. (2014). "Profile sampling to characterize particulate lead risks in potable water." Environ Sci Technol 48(12): Clement, M., et al. (2000). "A Practical Model for Estimating Total Lead Intake from Drinking Water." Water Res 34(5): Del Toral, M. A., et al. (2013). "Detection and evaluation of elevated lead release from service lines: a field study." Environ Sci Technol 47(16): Grayman, W. M. and S. G. Buchberger (2006). Fixture-Level Human Exposure Calculation Model. 8th Annual Water Distribution Systems Analysis Symp. Cincinnati. Hayes, C. R. and T. N. Croft (2014). Optimization of Plumbosolvency Control using Computational Modelling Techniques: A Demonstration Project for the Government of Alberta, Working with the City of Calgary and EPCOR (Edmonton). Hayes, C. R. and T. N. Croft (2012). "An Investigation into the Representativeness of Random Daytimes Sampling for Lead in Drinking Water, Using Computational Modelling." Journal of Water Supply: Research and Technology 61(3): Sandvig, A., et al. (2008). Contribution of Service Line and Plumbing Fixtures to Lead and Copper Rule Compliance Issues, AWWA Research Foundation. Schock, M. R., et al. (2014). "Importance of Pipe Deposits to Lead and Copper Rule Compliance." Journal - American Water Works Association 106: E336-E349. van den Hoven, T. (1987). "New Method to Determine and Control Lead Levels in Tap Water." Aqua AQUAAA 6.