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Presentations May 23 – 25, 2005 Portland, Maine

Presentations May 23 – 25, 2005 Portland, Maine For related information visit: http://www.newmoa.org/prevention/mercury/conferences. Background.

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Presentations May 23 – 25, 2005 Portland, Maine

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  1. Presentations May 23 – 25, 2005 Portland, Maine For related information visit: http://www.newmoa.org/prevention/mercury/conferences

  2. Background • Mercury release is still a pressing issue • Increasing number of fish consumption advisories due to Hg • Dental offices are targets of regulatory scrutiny • Growing trend for POTWs to require use of BMPs and separators

  3. Human Health Effects • Human Health concerns are the primary driver of low level Hg discharge limits • Even chronic low dose exposure is thought to be harmful, especially to the fetus and the developing infant • Human exposure primarily through fish consumption • Currently 45 states with fish consumption advisories due to Hg levels

  4. Dental-Unit Wastewater • Avg. settling velocity ranges within 16.56 to 65.7 cm/hr (specific gravity of amalgam = 11.6) • Over 90% of amalgam particulate will settle in 2 hours • Substantial amounts of dissolved Hg may be present • 0.368 mg/L dissolved Hg • 3.905 mg/L total Hg

  5. Forms of Hg Present in Dental-Unit Wastewater • Elemental mercury bound with other metals in amalgam, Hg(0) – 21,360 ppb • Free elemental mercury, Hg(0) – 24.6 ppb • Ionic mercury, Hg(+2) – 54 ppb • Monomethyl mercury, MeHg – 0.2778 ppb • Different forms of mercury have different toxicokinetics

  6. Bioavailability of Dental Hg • A small percentage of the Hg in dental wastewater is in forms that can be incorporated into organisms • MeHg and ionic Hg have been measured in surprising concentrations • ~97% of Hg in wastewater is in the form of Hg(0) bound in amalgam particulate

  7. Dental Hg Released to the Environment • Hg production per dentist is exceedingly variable • 484 mg/day (n=25, SD=420), from 1994 • 971 mg/day (n=32, SD=716), from 2005 • Units are in mg/Hg per chair per day • Samples collected after the chairside traps • Data is from U.S. Navy Dental Treatment Facilities

  8. What is an amalgam separator? • Devices used to take amalgam (andhence Hg) out of dental wastewater • 8-to-80% of Hg WWTPs influent arises from dental sources, dependent upon location (AMSA study >35%, NEORSD – 41%) • Separators vary in complexity, cost and efficiency • Even “low tech” systems appear to be effective

  9. Two Classes of Separators • Particulate Removal • Sedimentation (Specific Gravity amalgam=11.6) • Filtration • Centrifugation (Europe only) • Particulate and Dissolved Mercury Removal • Oxidation with chemicals to speciate Hg • Ion exchange resins capture Hg+2

  10. Amalgam Separators • Separators need routine inspection and maintenance • More complex systems fail in more ways • Need for an integrative approach to managing mercury in dental office • Need for a simplified way to recycle mercury wastes

  11. ISO 11143 Separator Standard • Laboratory made amalgam standard • 6 grams of amalgam3.15 mm to 500 microns • 1 gram of amalgam500 microns to 100 microns • 3 grams of amalgamless than 100 microns • Mixed in 1-liter of filtered tap water • Amalgam solution poured in separator • Effluent is filtered (12μm, 3μm, and 1.2μm), filters dried, and weighed • 95% removal efficiency, based on weight, needed to pass • Some areas call for 99% removal, e.g. RI, MN

  12. ISO 11143 Separator Standard • Measures ability of separator to remove lab generated particulate sample • May not accurately model real wastewater • Regulators use Hg concentration limits, not particulate removal

  13. Do Separators Really Work? Toronto, Ontario Data • Toronto – 5th largest city in North America; over 1,100 dental practices • Required separator installation by January 1st, 2002 • Since Installation of separators; 58% reduction in Hg levels in WWTP biosolids (sludge) • Hg in sludge reduced from 17 kg to 7 kg per month • Data obtained when compliance estimated to be 800 of 1100 clinics (~73%)

  14. Do Separators Really Work? • MCES is the POTW for the Minneapolis/St. Paul, Minnesota metro area • Study done in Hastings and Cottage Grove • 24 of 25 dentists in these communities participated in study • Separators in place for 3 months • 44% and 29% reductions in Hg levels in WWTP biosolids

  15. Do Separators Really Work? • Local POTW required Naval Base Great Lakes to install separators • Base has end-of-pipe Hg discharge limit of 0.5 g/liter, soon to be lowered to 0.1 g/liter • History of Hg exceedances from base • Dental clinics on base use 60,750 double spill amalgam capsules per year (~60 lbs of Hg)

  16. Do Separators Really Work? • First pretreatment system was installed in largest Navy clinic in 1996 • Since then all Navy dental clinics have systems installed • 52% decrease in Hg levels in local POTW sludge biosolids since separators installed • Yearly NOVs have decreased from 54 to 3

  17. Do Separators Really Work? • Duluth Minnesota active since 1993 • 50 dental practices with ~100 dentists • After separators installed Hg in biosolids decreased from 2.5 mg/kg to 0.19 mg/Kg • WWTP Hg influent has decreased from 0.18 lbs/day in 1993 to <0.02 lbs/day today • Hg in WWTP effluent decreased from 20.6 ng/liter to 1.9 ng/liter • Data from Denmark also supports efficacy of separators

  18. Residual Hg in Wastewater Lines • Residual Hg in wastewater lines can be substantial • Plumbing lines act as a separator • TCLP studies on wastewater lines show pipes themselves can exceed RCRA limits for Hg • Hg can be mobilized from amalgam in waste lines e.g. by acids and oxidizing line cleaners

  19. Residual Hg in Wastewater Lines *One value exceeded the 0.2 mg/L threshold for Hg in TCLP leachate

  20. Evaluation of Low Cost Chairside Filters as Amalgam Separators Sample Size Mean Hg Levels in mg Standard Deviation Filter Type • Units are in mg Hg per chair per daydischarged into plumbing system

  21. 100 m Cartridge 1 m Cartridge 1 m Bag 0.5 m Cartridge Removal Efficiency 44.6% 72.9% 95.8% 99.7% ISO 11143 Efficiency 97.58% ── ── 98.09% Calculated Removal Efficiencies • ISO 11143 testing completed by outside laboratory; empty test • Calculated removal efficiencies = (BHg – FHg / BHg) x 100; where BHg is the baseline Hg level, FHg is the amount of particulate Hg collected after the chairside filter)

  22. Why are we still using amalgam? • Amalgam still widely used but decreasing • Good physical properties • Marginal seal from corrosion products • Easy to place -- not technique sensitive • Cost effective • Long track record – over 150 years • Large installed base of amalgam means amalgam removal for years to come

  23. Amalgam Replacement Options • Gallium based alloys • 1 of 4 metals that are liquid near room temperature • Low vapor pressure • Direct condensed silver restorations • Cast metal alloys • Porcelain based restorations • Composite restorations (direct and indirect)

  24. Composite Restorations • Organic Polymer Matrix • BIS-GMA or UDMA • Inorganic filler particles • Glass, Silica, or Quartz • Coupling agents • Organosilanes • Initiator-accelerators system (photo or self cure) • Camphoroquinone is photo activator • Organic amines accelerate reaction • Chemical activation by organic amine and organic peroxides

  25. Composite Restorations • Composites more esthetic • Composites require more skill and time to place and finish • Wear issues are a concern – occlusion • Moisture control is crucial with composites – saliva prevents bonding to tooth • More costly than amalgam • Composites not indicated for restoration of large multi-surface carious lesions in posterior teeth

  26. Presentations May 23 – 25, 2005 Portland, Maine

  27. Western Lake Superior Sanitary District Mercury Reduction Program Tim Tuominen (218) 740-4815 tim.tuominen@wlssd.duluth.mn.us

  28. Early Efforts Started in 1990, included: • Reduced internal sources from incinerator scrubbers • Engineering study of end-of-pipe treatment options: $16.7 million / year (’93 dollars) to meet GLI • Implemented Industrial limits • Started dental waste management efforts • Improved waste management practices • Waste amalgam recycling

  29. Further Efforts • MercAlert - a solid waste source reduction effort • Worked with Industrial Customers: Potlatch, Haarman & Reimer, and LSPI using P2 to improve raw materials.

  30. Continued Efforts • HHW and Clean Shop collections • Zero Discharge Grant: Schools, Hospitals, and Dentists

  31. Recent Efforts: • Region effort eliminating mercury equipment in schools -MN Great Award • Fever thermometer exchanges • St. Louis River Beneficiary Group for Environmental Improvement Grant: WLSSD & NE MN Dental Society Amalgam separator purchase

  32. Working with the Dental Community • 56 of 57 offices have improved treatment systems installed • Project has been cooperative • State-wide effort is being developed, based upon voluntary WLSSD program • Working to get systems installed at last practice

  33. Species of Hg in Effluent

  34. Mercury in our Environment • WLSSD Effluent: 2.6 ng/L (0.4 grams/day) • St. Louis River: 3.1 ng/L (19 grams/day) • Rain water: 12 ng/l

  35. The Future • Future limits are very aggressive • Most treatment plants will not meet the new limits • If present reduction trends continue we will meet the limits most of the time • Suspended solids capture will be critical • Source reduction efforts continue to be an important factor

  36. Presentations May 23 – 25, 2005 Portland, Maine

  37. Reducing Mercury in Dental Office Wastewater: King County’s Experience 1990 – 2005 Patricia Magnuson Industrial Waste Program King County Department of Natural Resources and Parks

  38. King County Wastewater Treatment Division Sewer Service Area • 1.4 million people • Collect and treat municipal and industrial wastes • 200 mgd • 136 SIUs /286 other permitted • 3 mgd • 1300 dentists in about 900 offices

  39. King County’s concern with mercury in dental office wastewater in 1990 • 1989 NPDES violation of mercury at West Point Treatment Plant. Ecology required King County to investigate • No point sources found • Identified dental office wastewater as “significant and identifiable” source of mercury • 1991 -1994 Researched dental waste discharges and treatment options

  40. Findings at that time • Dentists contributed approx 14% of mercury to WWTP • Dentists were not in compliance with discharge limits • Amalgam separators can remove mercury • Chairside ASU • Screen and settlement Photo: Courtesy of: Thomas Barron, Civil Engineer, 925-283-8121 • tsbarron@attglobal.net

  41. Early policy choices • 1994 King County drafted a rule for dentists that required the installation of amalgam separators • 1995 King County decided to postpone the rule and work with dental community to achieve voluntary compliance

  42. King County’s Program: 1995 - 2000 • Intensive outreach program for dentists • Annual Poster • Monthly ads in local journal • Voucher Incentive Program • EnviroStars • Informational visits • Trade shows/mercury roundups

  43. Results in 2000 15% Compliance

  44. King County’s concern with mercury in dental office wastewater in 2000 • Maintain “marketability” of biosolids • Equity - need to treat different industry sectors equitably 100% Recycled

  45. Biosolids Quality • Majority of mercury from amalgam goes to biosolids. • Biosolids “Exceptional Quality” limit 17 mg/kg

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