Presentation on theme: "Presentations May 23 – 25, 2005 Portland, Maine For related information visit:"— Presentation transcript:
Presentations May 23 – 25, 2005 Portland, Maine For related information visit:
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 Background
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 Human Health Effects
Avg. settling velocity ranges within 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 mg/L dissolved Hg mg/L total Hg 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 – ppb Different forms of mercury have different toxicokinetics Forms of Hg Present in Dental- Unit Wastewater
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 Bioavailability of Dental Hg
Hg production per dentist is exceedingly variable 484 mg/day (n=25, SD=420), from 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 Dental Hg Released to the Environment
Devices used to take amalgam (and hence 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 What is an amalgam separator?
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 Two Classes of 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 Amalgam Separators
Laboratory made amalgam standard 6 grams of amalgam 3.15 mm to 500 microns 1 gram of amalgam 500 microns to 100 microns 3 grams of amalgam less 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 ISO 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 ISO Separator Standard
Toronto – 5 th largest city in North America; over 1,100 dental practices Required separator installation by January 1 st, 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%) Toronto, Ontario Data 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 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) 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 Do Separators Really Work?
Duluth Minnesota active since 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 Do Separators Really Work?
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 Residual Hg in Wastewater Lines
LocationSizeResidual HgTCLP HgTCLP Ag Virginia 0.75 inch 1,097 mg/kg0.019 mg/LND Maryland 2 inch 139,000 mg/kg mg/L * mg/L Maryland 1.5 inch 8,130 mg/kg0.035 mg/LND Maryland 0.5 inch mg/L0.137 mg/L Illinois 1 inch 3,292 mg/kg0.089 mg/L0.150 mg/L * One value exceeded the 0.2 mg/L threshold for Hg in TCLP leachate Residual Hg in Wastewater Lines
Chairside trap only µm cartridge µm bag µm cartridge µm cartridge Sample Size Units are in mg Hg per chair per day discharged into plumbing system Mean Hg Levels in mg Standard Deviation Filter Type Evaluation of Low Cost Chairside Filters as Amalgam Separators
0.5 m Cartridge 1 m Bag 1 m Cartridge 100 m Cartridge Removal Efficiency ISO Efficiency 44.6%72.9%95.8%99.7% 97.58%98.09% ISO testing completed by outside laboratory; empty test Calculated removal efficiencies = (B Hg – F Hg / B Hg ) x 100; where B Hg is the baseline Hg level, F Hg is the amount of particulate Hg collected after the chairside filter) Calculated Removal Efficiencies
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 Why are we still using amalgam?
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) Amalgam Replacement Options
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 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 Composite Restorations
Presentations May 23 – 25, 2005 Portland, Maine
Western Lake Superior Sanitary District Mercury Reduction Program Tim Tuominen (218)
Early Efforts Started in 1990, included: Reduced internal sources from incinerator scrubbers Reduced internal sources from incinerator scrubbers Engineering study of end-of-pipe treatment options: $16.7 million / year (93 dollars) to meet GLI Engineering study of end-of-pipe treatment options: $16.7 million / year (93 dollars) to meet GLI Implemented Industrial limits Implemented Industrial limits Started dental waste management efforts Started dental waste management efforts Improved waste management practices Improved waste management practices Waste amalgam recycling Waste amalgam recycling
Further Efforts MercAlert - a solid waste source reduction effort MercAlert - a solid waste source reduction effort Worked with Industrial Customers: Potlatch, Haarman & Reimer, and LSPI using P2 to improve raw materials. Worked with Industrial Customers: Potlatch, Haarman & Reimer, and LSPI using P2 to improve raw materials.
Continued Efforts HHW and Clean Shop collections HHW and Clean Shop collections Zero Discharge Grant: Schools, Hospitals, and Dentists Zero Discharge Grant: Schools, Hospitals, and Dentists
Recent Efforts: Region effort eliminating mercury equipment in schools -MN Great Award Region effort eliminating mercury equipment in schools -MN Great Award Fever thermometer exchanges Fever thermometer exchanges St. Louis River Beneficiary Group for Environmental Improvement Grant: St. Louis River Beneficiary Group for Environmental Improvement Grant: WLSSD & NE MN Dental Society Amalgam separator purchase
Working with the Dental Community 56 of 57 offices have improved treatment systems installed 56 of 57 offices have improved treatment systems installed Project has been cooperative Project has been cooperative State-wide effort is being developed, based upon voluntary WLSSD program State-wide effort is being developed, based upon voluntary WLSSD program Working to get systems installed at last practice Working to get systems installed at last practice
Species of Hg in Effluent DateTotal Mercury ng/L Dissolved Mercury ng/L Methyl Mercury ng/L 4/16/ /23/ /16/
Mercury in our Environment WLSSD Effluent: 2.6 ng/L (0.4 grams/day) WLSSD Effluent: 2.6 ng/L (0.4 grams/day) St. Louis River: 3.1 ng/L (19 grams/day) St. Louis River: 3.1 ng/L (19 grams/day) Rain water: 12 ng/l Rain water: 12 ng/l
The Future Future limits are very aggressive Future limits are very aggressive Most treatment plants will not meet the new limits Most treatment plants will not meet the new limits If present reduction trends continue we will meet the limits most of the time If present reduction trends continue we will meet the limits most of the time Suspended solids capture will be critical Suspended solids capture will be critical Source reduction efforts continue to be an important factor Source reduction efforts continue to be an important factor
Presentations May 23 – 25, 2005 Portland, Maine
Reducing Mercury in Dental Office Wastewater: King Countys Experience 1990 – 2005 Patricia Magnuson Industrial Waste Program King County Department of Natural Resources and Parks
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 King County Wastewater Treatment Division
King Countys concern with mercury in dental office wastewater in 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 Researched dental waste discharges and treatment options
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,
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
King Countys Program: Intensive outreach program for dentists Annual Poster Monthly ads in local journal Voucher Incentive Program EnviroStars Informational visits Trade shows/mercury roundups
Results in % Compliance
King Countys concern with mercury in dental office wastewater in 2000 Maintain marketability of biosolids Equity - need to treat different industry sectors equitably 100% Recycled
Biosolids Quality Majority of mercury from amalgam goes to biosolids. Biosolids Exceptional Quality limit 17 mg/kg
Mercury Limits King County Local Limits for discharge to sewer 0.1 mg/l for > 5000 gpd 0.2 mg/l for < 5000 gpd Limits apply to all businesses in King County sewer service area Local limits achievable at dental office with pretreatment
Goals for Regulatory Program Minimize paperwork for dentists Minimize expensive sampling Minimize long term program costs for K.C. Be equitable Highest compliance possible
Requirements by July 1, 2003: Use best management practices (BMPs) for amalgam waste; and Demonstrate compliance with K.C. Local Limits (0.2 mg/l) for mercury through ONE of three routes:
Routes to Compliance 1. Install and maintain an approved amalgam separator unit; or 2. Apply for and receive a permit to discharge; or 3. Be an exempt specialty or practice a. Orthodontist, oral surgeon, radiologist… b. Place or remove amalgams less than 3 days per year
Installation of K.C. approved amalgam separator unit = compliance No permit required No sampling required Maintain equipment Keep waste disposal records for at least 3 years Message to Dentists that Place or Remove Amalgam
King County Approved Separator List Lists main advantage is for determining compliance List development Required ISO certification – 95% Checked paper work only Photo Courtesy of DRNA APPROVED
King Countys Program: July 2001 – July 2003 Develop and distribute informational documents Web page Articles in local and state dental society journals Attend trade shows Voucher incentive program Personal visits by public health inspectors
King Countys Program After July 1, 2003 Random inspections of dental offices Goal of inspecting 10% per year Web page, brochures, follow up letters Enforcements, including fines
Results in % Compliance
Annual Median Mercury Concentration in Biosolids
Differences in ASU Installation in King County Mandatory Voluntary
Outreach + Regulations = Compliance Amalgam Separators Installed Data from Gail Savina and Olivia Chamberlain; KCLHWMP
More Information Patricia Magnuson King County Industrial Waste Program