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Managing Mercury in Dental Offices

Managing Mercury in Dental Offices. Greg Newman Division of Pollution Prevention and Environmental Assistance. OUTLINE. Background Mercury in North Carolina Mercury in Wastewater Sources of Dental Mercury Discharges Preventing Mercury Releases Treatment. Mercury: Background.

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Managing Mercury in Dental Offices

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  1. Managing Mercury in Dental Offices Greg NewmanDivision of Pollution Prevention and Environmental Assistance

  2. OUTLINE • Background • Mercury in North Carolina • Mercury in Wastewater • Sources of Dental Mercury Discharges • Preventing Mercury Releases • Treatment

  3. Mercury: Background

  4. Products / Chemicals Containing Mercury • Thermometers • Manometer (pressure gauges) • Tilt switches • Thermostats • Fluorescent Lights • Sulfuric Acid (lead smelting) • Caustic Soda (chloro-alkali) • Chlorine Bleach (chloro-alkali) • Chlorine Gas (chloro-alkali) • Textile fabric (biocides) • Overall Use of Mercury Down 97% (1980-96)

  5. Environmental Effects of Mercury • Once in water bacteria convert Hg to Methyl Mercury - Neurotoxin • Methyl Mercury Biomagnifies • Binds to Proteins of Fish • Bass & Bowfin Most Affected

  6. Mercury Emissions to the Environment • Total of 3300 tons annually • Natural Sources • Oceans, Rocks, Volcanoes, Plants

  7. US Manmade Mercury Sources • Combustion Contributes 83% of U.S. Hg Emissions (285 tons) • Mercury from Combustion Falls Back to Ground with Rain • Washes into Rivers and Lakes

  8. Mercury in Wastewater • POTWs Usually think in ppm or ppb • Need to Think in Sub-ppb (parts per trillion) • 1 fever thermometer (0.5 grams) contaminates 11 million gallons of water 0.2 0.012 0.065

  9. Mercury in North Carolina

  10. Fish Advisories in North Carolina

  11. Update on Mercury Situation in NC • Fish Consumption Advisories for Lumber River Basin, Baytree Lake, & added Phelps Lake in ‘96 • Total More than 10% of States Land Area • NC Advisories from Atmospheric Deposition • Phelps Lake is Land Locked (No major influent, surrounded by State Park)

  12. Dental Mercury Contributions

  13. Mercury from Dental Discharges • Estimates on POTW Mercury Loading from Dentists Range from Negligible to Nearly 60% of Total • Many POTWs Believe Dentists are one of the Last Direct Dischargers or Mercury Duluth, Minnesota 4

  14. Mercury from Dental Discharges • Amalgam 1:1 mix of Mercury & Alloy Powder • Only About 45% Ends Up in Tooth Filling (Rest down the drain through traps and vacuum system) • Major Amalgam Particles Caught in Screens, some smaller particles caught in traps • Significant Pass-thru of Minor Particles • Increased surface area of small particles increases mercury solubility

  15. Dental Waste Continued... • Low Flows (< 1 Gallon per patient) • High Concentration (1-15 ppm Hg) • Theoretically, 1 gallon Dental Wastewater at (3 ppm) puts 1 MGD over WQ Standard

  16. Preventing Mercury Releases

  17. Amalgam Management • Goal: Prevention of amalgam releases to the environment • Methods include: - product substitution- improved housekeeping- separation- recycling

  18. Amalgam Management – Priorities • Prevent introduction to City sewer • Prevent incineration (red bag waste) • Recycle or manage as hazardous waste • Keep mercury spill kit on site

  19. Dental Office Waste Management

  20. Amalgam Management MANAGEMENT STRATEGIES • Use precapsulated amalgam. • Establish contract with recycler - Recycle all contact and non contact mercury (list) • Amalgam traps and filters should be shipped to a recycler or collected by a hazardous waste hauler. Separate contact from non-contact amalgam • Change chair side traps once per week. Flush lines at end of the day and change traps in morning. • Use disposable traps as it is difficult to remove amalgam from reusable traps and the material is often washed to sewer

  21. Amalgam Management MANAGEMENT STRATEGIES • Don’t rinse traps or filters over drains - Retrieve excess amalgam with gauze and recycle. • Remove amalgam from instruments with gauze prior to washing and recycle. • Secondary filters in vacuum systems should be changed once per month or according to manufacturers specifications • Store any waste amalgam in designated airtight container. TRAINING • Train all employees • Maintain a log RESULTS • 75% removal of amalgam

  22. Mercury Treatment Equipment

  23. Dental Amalgam Wastewater Technologies • Screening Filters • Simple Wire Screens Protecting Vacuum Pumps • Change to finer mesh (20 for 100) close to 90% Removal • Sedimentation • Vary from simple inexpensive traps to large Multi- phase Units $200 - $1,000, claim 95% removal • Ion Exchange • Cationic & Anionic polymers capture small particles of Hg usually after sedimentation • $1,500 and up, claim 95% removal • Centrifuge • Spin larger particles out to the sides of the vacuum pump for collection • $2,500 and up, claim 95% removal • Cross flow microfiltration with precipitation • Traditional Metal Scavenging Polymers

  24. NC Efforts to Reduce Wastewater Dental Mercury • Tryon exploring permits • Whiteville and Fuquay-Varina strongly encourage / require installation of treatment equipment • Whiteville received grant to conduct evaluation of removal equipment

  25. Questions / Comments • Greg Newman (919) 715-6515 Greg_Newman@p2pays.org Web: www/p2pays/org

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