Greg Welter, O Brien & Gere Dan Giammar, Washington University in St. Louis Maureen Schmelling, DC Water

Transcription

1 Water Research Foundation # Impact of Galvanic Corrosion on Lead Release Following Partial Lead Service Line Replacement Greg Welter, O Brien & Gere Dan Giammar, Washington University in St. Louis Maureen Schmelling, DC Water

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6 Impact of Galvanic Corrosion on Lead Release Following Partial Lead Service Line Replacement Gregory Welter, PE, BCEE (O Brien & Gere Engineers) Daniel Giammar, Ph.D., PE (Washington University in St. Louis) Maureen Schmelling, (DC Water)

7 Galvanic Corrosion Following Partial Lead Service Line Replacement Water Research Foundation Project 4349 Major project sponsors: Water Research Foundation (WaterRF) District of Columbia Water and Sewer Authority (DC Water) Providence Water Supply Board (Providence Water) Principal Investigators and Other Key Personnel: Gregory Welter, PE BCEE, O Brien & Gere Engineers Daniel Giammar, PhD, PE, Washington University in St. Louis Abigail Cantor, PE, Process Research Solutions Yin Wang, Ph.D. Washington University in St. Louis Acknowledgements: DC Water Maureen Schmelling, Ying Tan, Hanna Belete, Pierre Constant, Rich Giani Providence Water Paul Gadoury, Norm Ripstein, George Solitro O Brien & Gere John Phillips, Rob Richards, Andrew Welter WaterRF project managers: Jonathan Cuppett, Michelle Suazo

8 The Lead Service Line Replacement Dilemma Extent of public utility control of service line varies and can stop at the main, property line, the shutoff, or meter box. The rest of the line, to the residence, is privately controlled. Lead service line replacements, whether regulatory required or part of infrastructure renewal, may be partial if private owner does not participate.

9 Galvanic Release due to Dissimilar Metals Typically, partial lead service line replacements (LSLRs) are accomplished using brass compression couplings. However, the dissimilar metals contact sets up conditions for galvanic release of lead to the water.

10 Components of the Project Literature review (too detailed for coverage in this webinar available in report and on WaterRF website) Laboratory experiments conducted with commercially available couplings (standard brass, brass dielectric, and all plastic) Conventional brass coupling Dielectric brass coupling, with plastic bushing All plastic transition coupling Review of field data from two lead service replacement programs: Washington, DC, and Providence, RI. Results of survey on typical kitchen use flow rates, and implications for sampling.

11 Outline Background and Motivation Experiments in this project Lab - Washington University in St. Louis Pilot - Fort Reno in Washington, DC Analysis of Data from Lead Service Line Replacement Programs Evaluation of Typical Faucet Flow Rates Conclusions and Recommendations

12 Laboratory Experiments Conventional Brass Brass Dielectric Low-lead Brass Plastic Plastic - External Connection PVC pipe (control) X X X X DC pipe X X X X X Providence pipe X X Duplicate experiments are conducted for the lead pipes. Ex-wired Plastic Plastic Brass Dielectric Brass

13 Experiment Operation Mon-Thurs flow cycle: 6 h stagnant 15 min flow 17 h stagnant 3 min flow Weekend flow cycle: 6 h stagnant 15 min flow 65 h stagnant 3 min flow Flow velocity of 1 ft/s through lead pipe (3.6 L/min) Sample at end of stagnation periods (just before starting flow) Replace the recirculation reservoir each week and acidify the old reservoir for measurement of any lead accumulation in the reservoir.

14 Operation Cycle Red = sample collection. Analyze for: Total and dissolved lead and copper ph and free chlorine

15 Synthetic Providence Water Water composition parameter Target range Actual value 1 ph 9.5 to to 9.8 Free residual chlorine, mg/l as Cl 2.16 to.5.42 Total alkalinity, mg/l as CaCO to TDS, mg/l 97 to Total hardness, mg/l as CaCO to Chloride, mg/l 17.3 to Sulfate, mg/l 2. to The actual value of the ph was determined from daily measurements, and the values for the other parameters were determined from the recipe used to prepare the synthetic Providence Water.

16 Dissolved Pb (ug/l) Total Pb (ug/l) Conditioning of Lead Pipes 6-h stagnation average from final 4 weeks April-May 211 Dissolved and total lead concentrations are similar. 12 Dissolved Lead 12 Total Lead A 9A 1B 2B 1A 9A 1B 2B

17 Connected Lead Pipes and Copper Tubing Coupling conventional brass all plastic Effect of connection on dissolved and total lead release. Differences in lead release with increasing stagnation time. Localization of lead release.

18 Dissolved Pb (µg/l) Total Pb (µg/l) Lead Concentrations for Connected Pipes 8 6 Dissolved Lead plastic-1 plastic-2 brass-1 brass Total Lead plastic-1 plastic-2 brass-1 brass cond weeks cond weeks Dissolved and total lead concentrations are both significantly higher for lead and copper connected with brass. Effect is more pronounced for total lead. Elevated lead concentrations persist for at least six weeks.

19 Dissolved Pb (µg/l) Total Pb (µg/l) Effect of Stagnation Time Dissolved Lead 6-h stagnation 65-h stagnation h stagnation 65h stagnation Total Lead plastic-1 plastic-2 brass-1 brass-2 plastic-1 plastic-2 brass-1 brass-2 Dissolved lead increases with increasing stagnation time. Total lead increases to very high concentrations (1-3 mg/l) with an increase in stagnation time from 6 to 65 hours. Particulate lead is the dominant form of released lead.

20 Synthetic Washington, DC Water Water composition parameter Target range Actual value Actual value with elevated CSMR ph Combined chlorine, mg/l as Cl to Total alkalinity, mg/l as CaCO 3 49 to TDS, mg/l 126 to Total hardness, mg/l as CaCO to Chloride, mg/l 3 to Sulfate, mg/l 4 to Orthophosphate, mg/l as PO to

21 Dissolved Pb (µg/l) Total Pb (µg/l) Conditioning of DC Lead Pipes 6-h stagnation Average from final 3 weeks ph ~ 7.7 chloramines = 3.7 mg/l Cl 2 alkalinity = 76 mg/l CaCO 3 orthophosphate = 2.47 mg/l PO 4 Dissolved Lead Total Lead A 3A 4C 4E 2A 3A 4C 4E

22 Dissolved Lead (µg/l) Total Lead (µg/l) Control Experiments with Couplings Copper Tubing (24 ) PVC Pipe (24 ) samples for analysis flow meter Coupling conventional brass brass dielectric low-lead brass all plastic recirculation reservoir (1 L) 6-h stagnation average from 4 weeks 45 Dissolved Lead 45 Total Lead h 65h h 65h Plastic LL-brass-1 LL-brass-2 Brass-die Brass Plastic LL-brass-1 LL-brass-2 Brass-die Brass

23 Dissolved Pb (µg/l) Total Pb (µg/l) plastic-1 plastic-2 brass-1 brass-2 Connected DC Lead Pipes Dissolved Lead 35 plastic-1 3 plastic-2 25 brass-1 brass Total Lead cond Weeks cond Weeks Dissolved and total lead concentrations are both significantly higher for lead and copper connected with brass. Effect is more pronounced for total lead. Elevated lead concentrations persisted for at least six weeks. Concentrations were not as high as for the Providence pipes.

24 Dissolved Pb (µg/l) Total Pb (µg/l) Effect of Stagnation Time Dissolved Lead Total Lead h 65h 6 5 6h 65h plastic-1 plastic-2 brass-1 brass-2 plastic-1 plastic-2 brass-1 brass-2 Dissolved lead does not increase significantly with increasing stagnation time. Total lead does increase with increasing stagnation time. Particulate lead is the dominant form of lead released at longer stagnation times.

25 L) L) Pb conc (µg/l) Pb conc (µg/l) Pb conc (µg/l) Pb conc (µg/l) DC Lead Pipes with External Connection a. Plastic -1 Plastic 1 particulate Pb dissolved Pb b. -2 Plastic 2 particulate Pb dissolved Pb no wire with wire no wire no wire with wire no wire c. Brass-die-1 Galvanic currents of 2-4 µa e. Brass-1 particulate Pb dissolved Pb particulate Pb dissolved Pb 4 35 d. Brass-die-2 Divergent behavior of duplicate particulate Pb pipes 3 dissolved Pb indicates 25 that pipes can have different 2 susceptibility to galvanic corrosion Only a portion of lead oxidation results 5 in lead in the water f. Brass-2 particulate Pb 213 Water Research dissolved Foundation. Pb ALL RIGHTS RESERVED.

26 Total Pb (µg/l) DC Lead Pipes with Different Connections 35 6-h stagnation max 75 th percentile median Mean 25 th percentile min Plastic Plastic -ex Brass die LL-Brass Brass Lead release: brass > low-lead brass > brass dielectric > plastic with wire > all-plastic Effect of lower lead release from low-lead brass coupling is small relative to effect of galvanic corrosion. Different behavior of duplicates, especially for plastic with the wire.

27 Total Pb (µg/l) Total Pb (µg/l) Total Pb (µg/l) Total Pb (µg/l) a. Plastic Localization of Lead Release plastic-1 plastic b. Plastic with Wire plastic-ex-1 plastic-ex-2 With galvanic corrosion, highest lead concentrations are near junction. Similar observations for dissolved lead c Brass Dielectric brass-die-1 brass-die Brass d. brass-1 brass Copper Lead Copper Lead Coupling Sequential Profile Samples Coupling Sequential Profile Samples

28 Key Findings from Laboratory Experiments More lead was released with connection methods in which galvanic corrosion was possible. Stagnation time strongly affected lead concentrations. Pipes have different susceptibility to galvanic corrosion. Dielectric couplings resulted in lower lead release but did not prevent galvanic corrosion. Low-lead brass resulted in less release, but effect was minimal compared to increase from galvanic corrosion. Impacts may subside over the long-term (several months).

29 Outline Background and Motivation Experiments in this project Lab - Washington University in St. Louis Pilot - Fort Reno in Washington, DC Analysis of Data from Lead Service Line Replacement Programs Evaluation of Typical Faucet Flow Rates Conclusions and Recommendations

30 Experiments at Fort Reno Water Quality Office once-through flow three 3-minute periods of flow per day during weekdays sampled after 6 h stagnation water from distribution system two test racks with three different couplings and harvested lead pipe one control rack with PVC pipe in place of lead.

31 Experiments at Fort Reno Water Quality Office once-through flow three 3-minute periods of flow per day during weekdays sampled after 6 h stagnation water from distribution system two test racks with three different couplings and harvested lead pipe one control rack with PVC pipe in place of lead. Photograph during conditioning period (no copper pipe or couplings)

32 Total Lead (ug/l) Lead Release Over Time Total Lead 1 1 plastic had internal connection no connection Harvested and conditioned lead pipes 1 brass (6a) dielectric (6b) 1 plastic (6c) 1 Lead concentrations decline with time, but spikes of high lead occur over the entire year. No clear differences in trend or frequency of spikes with different couplings. Similar observations observed for duplicate pipe runs.

33 Dissolved Lead (ug/l) Lead Release Over Time Dissolved Lead 1 1 conditioning plastic had internal connection no connection Harvested and conditioned lead pipes 1 1 brass (6a) dielectric (6b) plastic (6c) 1 Dissolved lead concentrations are lower than the total and do not have the periodic spikes in concentration. Similar concentrations achieved for all connection methods.

34 Total Lead (ug/l) Lead Release Over Time Total Lead 1 New lead pipes brass (2a) dielectric (2b) plastic (2c) 1 Even new lead pipes had periodic spikes in concentration. Overall downward trend still observed. Still no clear differences among connection methods.

35 Total Lead (ug/l) Comparison of Connection Methods 1 Brass Dielectric Plastic max mean 75 th percentile median 25 th percentile min 1 Harvested and conditioned lead pipes Similar median concentrations reached for most pipe runs. As much variability among replicate pipe runs for a given connection than between connection methods.

36 Differences in Experimental Methods Parameter Laboratory Fort Reno Implication for Results flow path recirculating once-through Lead accumulates over one week in laboratory flow rate general 1.4 gal/min (5.3 L/min) 2.25 gal/min (8.5 L/min) Particulate lead more likely to be released at higher flow rate sampling flow rate.26 gal/min (1 L/min) ~2.65 gal/min (9.9 L/min) Particulate lead more likely to be released at higher flow rate flow duration 45 min/day on weekdays 9 min/day on weekdays, with three 8-hour stagnation periods per day Longer periods of flow could result in faster passivation, but trend is actually the reverse. total dissolved solids 31 mg/l mg/l Affects water conductivity, which can influence corrosion other water composition Synthetic water Actual distribution system water Synthetic water does not have dissolved organic carbon, silica, or trace constituents of the actual water that may influence corrosion.

37 Outline Background and Motivation Laboratory in this project Lab - Washington University in St. Louis Pilot - Fort Reno in Washington, DC Analysis of Data from Lead Service Line Replacement Programs Evaluation of Typical Faucet Flow Rates Conclusions and Recommendations

38 Field data from Washington, DC, LSLR program

39 9th %-ile Lead (ppb) Field data from Washington, DC, LSLR program Washington DC - 26 Post Partial Data 9th %-ile Values (511 data points) Numbers of samples in each bin st Draw - 9th-%ile 2nd Draw - 9th %-ile Action Level Days from Partial LSLR to Sampling *9th %-ile value for 1st draw in -3 day bin is 234 ppb

40 Lead (ppm) Field data from Providence, RI, LSLR program Providence Water Post-Partial LSLR Data (524 Numbers data points of samples from in each 27 bin to Average 9th %-ile Action Level Days from Pipe Replacement to Sampling

41 Field data from Providence, RI, LSLR program Special study conducted to characterize phenomenon of post partial LSLR lead spiking. Study found that 9 th percentile concentrations for the 21 addresses were at16 ppb at 18 days after replacement (which was the end of the data collection.)

42 Survey of typical water usage flow rates Objective: What is the flow rate for typical household kitchen faucet use? That is, when the user is not constrained by concerns about complete capture, or using a typical sample container with narrow opening. **************************************** Survey conducted with 45 participants, at 23 residential locations, each asked to time the filling of a gallon container when using what they considered to be their normal use rate.

43 Number of tests at each flow rate Survey of typical water usage flow rates Median reported test of 1.43 gpm Reported kitchen use flow rates (gpm) This survey suggests that the typical consumer use flow rate from a kitchen faucet is approximately 1.4 gpm.

44 Project Conclusions Galvanic release due to dissimilar metals was found to be statistically significant in magnitude in lab experiments. The duration of elevated levels can have a duration on time-scales of months, based on both pilot experiments and field observations. At higher flow rates, differences in galvanic release may be overshadowed by other release mechanisms. In both extended pilot experiments and documented field experience, elevated lead release reduced to lower levels after several months (approximately four to six).

45 Recommendations Utilities might consider use of nonconductive transition couplings to avoid galvanic effect. Implications for electrical grounding should be considered (as discussed in the report.) Enhanced customer outreach and temporary provision of point-of-use filters can mitigate lead release following partial LSLRs. Use of typical flow rates during sampling should be encouraged. use of wide-mouth sampling containers, explicit encouragement to sampler of normal usage flow rates

46 Questions and Final report is now available from the Water Research Foundation. Wang, Y., Mehta, V., Welter, G.J., and D.E. Giammar, Effect of connection methods on lead release from galvanic corrosion, Journal American Water Works Association, E337-E351, 213. Wang, Y., He, J., Mehta, V., Welter, G.J., and D.E. Giammar, Impact of galvanic corrosion on lead release from aged lead service lines, Water Research, 46: , 212.