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Lead in New Buildings: UNC CHAPEL HILL Marc Edwards.

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Presentation on theme: "Lead in New Buildings: UNC CHAPEL HILL Marc Edwards."— Presentation transcript:

1 Lead in New Buildings: UNC CHAPEL HILL Marc Edwards

2 Background: Lead in New Buildings. Background: Lead in New Buildings. Preliminary Findings on Lead at UNC Preliminary Findings on Lead at UNC –Focus on the worst samples –How bad is/was the problem? Mitigating 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 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 up to 8% lead by weight

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

6 Why Leaded Brass in the First Place? Pb (up to 8% by weight) added to brass in order to: 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

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

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

9 Sampling Day # Pb (ppb) LCR Action Level: 15 ppb Test Water

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

11 10x Lower pH-Lower Alkalinity Water more aggressive Sampling Day # Pb (ppb) LCR Action Level: 15 ppb Low Alkalinity- Low pH Water NSF Test Water

12 UNC LEAD PROBLEM UNIVERSITY WAS VERY AGGRESSIVE IN SEEKING OUT “WORST CASE” SAMPLES 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) MANY SAMPLES COLLECTED WITH ALARMING LEVELS OF LEAD (> 500 ppb)

13 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 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 Lead values in recent sampling using conventional approaches indicates a significant, lower level lead problem, consistent with brass in new builds

14 “Beres” Samples 6 samples collected afternoon of 2/13/07 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 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) No building flushing at the time and representative of water people were drinking (but not first draw) 5 of 6 samples tested: 5 of 6 samples tested: Highest lead was 3.3 ppb

15 “Beres” Samples (Cont’d) 143 – 313 ppb Cu 143 – 313 ppb Cu ppb Zn ppb Zn 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 (7): ; doi: /chemse/bjl010 Group taste threshold for Cu +2 = 400 ppb

16 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 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 Flushing drops lead by removing sediments and hastening formation of protective film on brass

17 CAUSE OF THE LOW LEVEL LEAD PROBLEM CAUSE OF THE LOW LEVEL LEAD PROBLEM 8.0 x in 2 /mL

18 Meringue dezincification > pH 8.2 > pH 8.2 High Ratio High Ratio –Cl - :HCO 3 - Hot Water Hot Water Zinc enriched scale forming in brass from home with complaint elsewhere in water system

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

20 OWASA Lead Study (12 waters x triplicate conditions)

21 Preliminary Trends (OWASA RESEARCH)

22 Unusual problem can get better at lower pH!

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

24 Acknowledgements UNC Administration UNC Administration OWASA OWASA


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