1 / 24

Lead in New Buildings: UNC CHAPEL HILL

Lead in New Buildings: UNC CHAPEL HILL. Marc Edwards. Background: Lead in New Buildings. Preliminary Findings on Lead at UNC Focus on the worst samples How bad is/was the problem? Mitigating the Problem: Short-term: Minimizing Exposure/Flushing

Albert_Lan
Download Presentation

Lead in New Buildings: UNC CHAPEL HILL

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lead in New Buildings:UNC CHAPEL HILL Marc Edwards

  2. Background: Lead in New Buildings. • Preliminary Findings on Lead at UNC • Focus on the worst samples • How bad is/was the problem? • Mitigating the Problem: • Short-term: Minimizing Exposure/Flushing • Intermediate-term: Fine-tuning the Chemistry • Longer-term: Changing the Plumbing Code

  3. The Cause of the Problem“Lead Free” Brass • 1986 Safe Drinking Water Act Lead Ban • Pipes and solders < 0.2% lead by weight • Brass < 8% lead by weight Lead free brass can legally contain up to 8% lead by weight

  4. Also pumps, valves, water meters, backflow preventors, etc.

  5. Why Leaded Brass in the First Place? • Pb (up to 8% by weight) added to brass in order to: • seal leaks • improve corrosion resistance • ease machining of intricate brass devices Most modern brass products contain < 3% Pb

  6. Other information • Higher purity waters (lower alkalinity, etc) more likely to leach lead from brass • Rainwater and distilled water extremely aggressive • Water at UNC is very pure • Corrosivity mostly countered by raising pH and adding inhibitor

  7. In most cases lead leaching from brass drops off with age…

  8. 40 30 20 Pb (ppb) LCR Action Level: 15 ppb 10 Test Water 0 3 4 5 10 11 12 17 18 19 Sampling Day #

  9. But some waters are more aggressive to brass, and cause lead leaching to rise for a time before falling…

  10. 40 30 Low Alkalinity- Low pH Water 20 Pb (ppb) LCR Action Level: 15 ppb 10x NSF Test Water 10 0 3 4 5 10 11 12 17 18 19 Sampling Day # Lower pH-Lower Alkalinity Water more aggressive

  11. UNC LEAD PROBLEM • UNIVERSITY WAS VERY AGGRESSIVE IN SEEKING OUT “WORST CASE” SAMPLES • Removed brass plug to sample water from backflow preventor • Removed aerators to sample faucets • Sampled hot water MANY SAMPLES COLLECTED WITH ALARMING LEVELS OF LEAD (> 500 ppb)

  12. No alarming lead values came from appropriate samples of drinking water…. • Removing brass plugs and aerators before sampling, creates metal “turnings,” essentially adding fine pieces of brass to samples and giving high lead values • Lead values in recent sampling using conventional approaches indicates a significant, lower level lead problem, consistent with brass in new builds

  13. “Beres” Samples •  6 samples collected afternoon of 2/13/07 • Caudill Labs floors G, 1 and 3 specifically the Men's restroom faucets and the drinking fountains in the SW corridor • No building flushing at the time and representative of water people were drinking (but not first draw) 5 of 6 samples tested: Highest lead was 3.3 ppb

  14. “Beres” Samples (Cont’d) • 143 – 313 ppb Cu • 25 - 270 ppb Zn Group taste threshold for Cu+2 = 400 ppb Evaluation of Copper Speciation and Water Quality Factors That Affect Aqueous Copper Tasting Response Jonathan D. Cuppett, Susan E. Duncan and Andrea M. Dietrich Chemical Senses 2006 31(7):689-697; doi:10.1093/chemse/bjl010

  15. The lower level lead problem has responded well to flushing and cleaning of aerators • Building pipes were not thoroughly cleaned with aerators off when commissioned, or if it was cleaned, it was not successful • Flushing drops lead by removing sediments and hastening formation of protective film on brass

  16. CAUSE OF THE LOW LEVEL LEAD PROBLEM 8.0 x 10-3 in2/mL

  17. Meringue dezincification • > pH 8.2 • High Ratio • Cl-:HCO3- • Hot Water Zinc enriched scale forming in brass from home with complaint elsewhere in water system

  18. Turner Diagram (15 mg/L hardness, 14 mg/L Cl-)

  19. OWASA Lead Study(12 waters x triplicate conditions)

  20. Preliminary Trends(OWASA RESEARCH)

  21. Unusual problem can get better at lower pH!

  22. Legislation • Lead Free Drinking Water Act • Would reduce allowable lead to 0.25% • Reintroduced a few weeks ago • CA Assembly Bill 1953 • Limits the amount of lead in brass at wetted surfaces to < 0.25%

  23. Acknowledgements • UNC Administration • OWASA

More Related