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Meeting the Lead and Copper Rule Requirements

Meeting the Lead and Copper Rule Requirements. Alabama-Mississippi AWWA Education Workshop January 2014 Vernon L. Snoeyink University of Illinois. What should you expect from this presentation?. An understanding of the regulations and health effects of Pb and Cu

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Meeting the Lead and Copper Rule Requirements

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  1. Meeting the Lead and Copper Rule Requirements Alabama-Mississippi AWWA Education Workshop January 2014 Vernon L. Snoeyink University of Illinois

  2. What should you expect from this presentation? • An understanding of the regulations and health effects of Pb and Cu • A discussion of possible changes to the Lead and Copper Rule (LCR) • Important concepts • Scale formation and metal ion release • Scale stability and conversion issues • Constant pH stabilizes scale • Phosphate inhibitors reduce Pb solubility

  3. Copper Regulations • Action Level (AL) is 1.3 mg/L (90th percentile value) • AL samples: 1 liter first draw after 6 hours of stagnation • Basis: • Health reference: prevent nausea • SMCL: 1.0 mg/L based on taste and staining Ref: Advances in Water Research, Oct-Dec 2013, vol. 23, no. 4. Ref for Cu Corrosion: Chapter by Schock in Water Quality &Treatment, 6th Ed. AWWA/McGraw Hill, 2011

  4. Copper Control • In general, pH below 7 causes high Cu • Corrosion produces scale, and scale solubility determines Cu concentration • Cu concentration depends on pH, type of scale that forms, and alkalinity, and whether the pipe is new • Low pH (~7 or less) and high alkalinity (~ 300 mg/L as CaCO3) AL exceedance • Reduce Cu by increasing pH (if CaCO3 doesn’t precipitate) or orthophosphate Ref: S. Grace et al. “Control of new copper corrosion in high-alkalinity drinking water”JAWWA Jan. 2012

  5. Lead Regulations and Sources • AL is 15 μg/L (90th percentile) • Lead service lines & lead/tin solder outlawed in 1986 • Brass fixtures in homes, meters, water coolers etc. • The LCR (1991) says Pb ≤ 8 % • As of Jan 2014: Pb ≤ 0.25% of wetted surface of fixtures (2011 Safe Drinking Water Act Amendment) • Proposed revision to the LCR expected in 2014. Speculation only on what it might include

  6. How does Lead Get Into Drinking Water?

  7. Health Effects of LeadCDC: “No Safe Level” • Health effects related to blood lead levels (CDC: 5 μg/dL) • Infants and young children most susceptible • Primary source is lead paint dust • Neurological damage, impact on IQ, probable human carcinogen (renal tumors in rats) • MCLG of zero • Brown, M. J.; et al. Association between children's blood lead levels, lead service lines, and water disinfection, Washington, DC, 1998-2006. Environ Res 2011, 111 (1), 67-74. • Brown, M. J.; Margolis, S. Lead in drinking water and human blood lead levels in the USA. Morbidity and Mortality Weekly Report 2012, 61(Suppl; August 10, 2012), • 1-9. • Wat. Qual. &Treat., 5th Ed, Amer Wat. Works Assoc. , McGraw Hill, 1999 • Edwards et al. ES&T Jan 27, 2009

  8. The Presence of Lead Hurts Public Confidence Good Housekeeping, Feb. 2005 issue

  9. Pb in water usually comes from Pb scales • Pb  Pb2+ + 2e (corrosion) • Electron acceptors: O2, HOCl, OCl-, NH2Cl • Pb scales: • Lead carbonates: PbCO3 & Pb3(CO3)2(OH)2 • Lead phosphates: Pb3(PO4)2 & Pb5(PO4)3OH • PbO2 may also be formed if free chlorine is used in the distribution system • Non-crystalline lead solids and non-lead solids may be important

  10. We have 3 alternatives for using water quality to control Pb • Use orthophosphate, PO4, pH 7.2-7.8 • Use pH 9 -9.5 with an alkalinity > 35 mg/L as CaCO3 • Use free chlorine to form PbO2 The diagram on the next slide can be used to explain these options

  11. pC-pH Diagram shows pH range of low solubility Schock, USEPA

  12. BSE Image Al Ca Fe Si Mn P Pb Elemental Distribution – Chicago, ILRed Color is proportional to element densityNote the location of most of the lead

  13. Washington, D.C. Change from secondary disinfection with free chlorine to monochloramine led to severe LCR violation • Refs: • EPA website • Schock and Giani, ProcWatQual Tech Conf, San Antonio, Nov 2004, AmerWat. Wrks Assoc., Denver

  14. 2001 – 2002 Lead AL was exceeded • 90th percentile was 75 ppb) • The Washington Aqueduct (WA) treats Potomac River water and sells it to Washington DC, Arlington County and Falls Church. • DC WASA (now DC Water) is responsible for meeting the AL • WA is responsible for treating water • Arlington Co and Falls Church never exceeded the AL

  15. Lead Service Lines

  16. DC Lead Compliance History Schock and Giani, 2004

  17. PbO2 rapidly converts to Pb2+ when free chlorine is changed to NH2Cl Very likely: • Pb0 is the electron donor • PbO2 is the electron acceptor Pb0 + PbO2 + 4 H+ 2 Pb2+ + 2 H2O • Product is Pb2+ • Reaction is very rapid IF • PbO2 is in contact with lead pipe • Or if PbO2 is in outer layer and scale is conducting • PO43- must be present to convert Pb2+ to scale, to prevent high Pb concentrations

  18. Lead Profiles show that 1-liter first-draw samples do not give the highest lead concentration

  19. Peak lead values occur in the service line 100 NH2Cl 10 Free Cl Schock and Giani, 2004

  20. Water Quality Affects Scale Properties. Keep pH constant • At Washington Aqueduct, variable pH: • 7 to 8.5: high in winter, low in summer • Cause: post filter lime feed turbidity • Alkalinity: typically 60 mg/L as CaCO3 but highly variable; high in summer

  21. Desktop Study Showed 1) High pH not an option 2) o-PO4 best • CaCO3 precipitated above pH 8.5 but 9+ required • o-PO4 (H3PO4) likely best • Trial: apply to part of the distribution system before full-scale • Recommended pipe loop study to optimize treatment

  22. Full-Scale Implementation • Elevated total coliform counts, but no Coliform Rule violation • Colored water complaints in DC (1-2 a day). Caused by the phosphate? • Unable to flush prior to implementation • Lessons learned: • Flush before implementation • Document quality before implementation • Announce implementation before actual change

  23. Pipe Loop Study Design • Evaluate alternate control strategies • Use harvested lead service lines • Seven operating conditions, three loops each (21 loops total)

  24. Loop 4 vs 6 show PO4 Effect

  25. Results of Pipe Loop and Full Scale Study • No reason to use zinc orthophosphate instead of phosphoric acid as PO4 source • Lowering the chloramine dose did not reduce lead concentrations • Application of 3.5 mg/L H3PO4 as PO4 to the full scale system achieved compliance in the 1st full sampling period.

  26. Results of Pipe Loop and Full Scale Study • Lead levels continued to decrease as the PO4 dose was lowered from 3 to 1 mg/L (in pipe loop) • No evidence of an effect of a chlorine burn on lead levels after conversion to a Pb(II) scale • Lead concentrations are higher the higher the temperature

  27. LCR Lead Compliance Data PO4 feed started in fall 2004 at 3.5 mg/L as PO4

  28. What Is Occurring Because of DC Experience • The“action level” has become a “de facto” MCL • Confidence of public in water supply • EPA taking closer look at LCR • EPA examining LSL sampling times (not just first draw)

  29. Chicago Case History • Lake Michigan water, Alk ~ 100 mg/L, Ca ~ 2 mM, Alum coagulation, free chlorine, ortho plus polyphosphate inhibitor • Problem: phosphate forms a precipitate with residual aluminum that increases resistance to water flow in pipes • Ref: Atasi et al., Proc AWWA Annual Conf., Orlando, 2004

  30. Aluminum Phosphate: Chicago Case History • 1 mg/L as PO4 of an ortho-polyphosphate blend is added to control lead release from lead service lines • Precipitation of AlPO4 forms fine particles that deposited on walls of a 72” and a 90” cement lined mains • Residual Al in the summer is ~ 175 μg/L • C-factor was reduced from about 135 to 95

  31. Recent Chicago Results Del Toral et al, ES&T 2013 • LCR values for the last decade are ~6 ug/L • Peak values are service line samples and are ~ 2xAL • LSL disturbances cause the highest values (construction, LSL leak repair, meter installation…) • Should the LCR be changed to base compliance on the sample from the LSL?

  32. Important remaining questions: The service line problem • Replacement of lead service lines poses a serious problem. • Partial lead service line replacement of questionable benefit and may worsen the situation • Full service line replacement is costly and especially difficult to mandate in our old large cities

  33. Final Thoughts • Lead in drinking water is an important problem that will be with us for awhile. • The low lead content requirement for brass will help decrease the problem • We will have to find some way to make the lead service line problem go away

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