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King County regulations for dental wastewater discharged to the sewer


From King County, Washington Wastewater Treatment Division

http://dnr.metrokc.gov/wlr/indwaste/dentists.htm

Dentists must comply with King County regulations that limit the amounts of mercury and silver in wastewater they discharge to King County sewers.

The King County Industrial Waste Program wants to help dentists join with us in keeping these harmful pollutants out of the environment. To do this, we have prepared the following documents:

Dental wastewater fact sheet, which gives over-all information about how to comply.

How to prove you meet the mercury limit for dental wastewater without amalgam separators

Companies that transport dental office waste to licensed TSDRs (treatment, storage, disposal, or recycling facilities)

Amalgam separators approved by King County

If you have questions or comments, please e-mail Patricia Magnuson, telephone her at (206) 263-3021, FAX her at (206) 263-3001, or write her at King County Industrial Waste Program, 130 Nickerson Street, Suite 200, Seattle, WA 98109-1658.


Useful links for dentists:

Local Hazardous Waste Management Program (King County)--waste directory.

Naval Dental Research Institute--dental mercury environmental issues (outside link)

Environmental Protection Agency--mercury (outside link)

City of Palo Alto, CA--dental waste and other useful links (outside link)


Dental wastewater fact sheet:

How to meet King County regulations for wastewater discharged to King County sewers

Wastewater discharged by dental offices to the King County sewer system must meet limits on amounts of mercury and silver as described in King County Code--Title 28 and Public Rule PUT 8-13 (PR).

After much research, the King County Industrial Waste Program has identified three dental-office practices that will result in wastewater from dental offices meeting King County limits for mercury and silver.

If you do these practices, King County will accept them as proof that your office is in compliance and will not require that you sample your wastewater or obtain a permit to dispose of wastewater into the sewer system.

Ways to meet the limits other than these three practices may be acceptable if you can show that they work. To do this, see the document on how to prove you meet the mercury limit for dental wastewater without amalgam separators.

For the next 12 months, Public Health - Seattle & King County field staff will visit dental offices to explain these three practices and assist, not to take enforcement action.

Afterward, investigators from the King County Industrial Waste Program will begin inspecting dental offices to see that they meet King County limits. (See the section at the end of this fact sheet called "mercury and silver limits: authority and enforcement.")

The three practices are:

1. Follow Best Management Practices for amalgam wastes.

2. Properly handle spent fixer used in X-ray processing.

3. Install amalgam separators at each chair or in a central location where amalgam is removed or placed.

Details about the three practices and when to apply them follow:

1. Follow Best Management Practices for amalgam wastes

  • Keep amalgam out of sinks and never rinse amalgam waste down the drain.
  • Clean or replace chair-side traps on a regular schedule and properly dispose of amalgam waste.
  • Clean vacuum pump filters regularly, according to the manufacturer's recommendations, and properly dispose of amalgam waste.
  • Send amalgam wastes to a licensed TSDR (treatment, storage, disposal, or recycling facility). Here is a link to a list of companies that transport waste to a TSDR.
  • Maintain all disposal records on site for 3 years.

King County expects all dental offices to use these Best Management Practices right away.

2. Properly handle spent fixer used in X-ray processing

  • Collect spent fixer and have it disposed of by a vendor who will recover the silver in it.
  • (OR) If you prefer to treat the fixer on site and dispose of it down the drain, you must remove the silver by installing two chemical recovery cartridges (CRCs) in a series. Cartridges must be sized and maintained according to the manufacturer's recommendations. For more information on cartridges, visit this Web site.
  • Maintain all disposal or maintenance records on site for 3 years.

King County expects all dental offices to begin managing spent fixer properly right away.

3. Install amalgam separators at each chair or in a central location where amalgam is removed or placed

  • Separators must be approved by King County. Here is a link to a list of King-County-approved amalgam separators. If you want to install a unit that has not been approved by King County, contact Bruce Tiffany with the King County Industrial Waste Program to learn how to obtain approval.
  • Maintain the unit and dispose of wastes according to manufacturer's recommendations.
  • Keep installation, maintenance, and disposal records on site for 3 years.

Installing amalgam separators requires time, planning, and budgeting. Therefore, we do not expect dental offices that install separators or otherwise prove they meet King County limits to be in compliance until the following dates.

  • After July 1, 2002: New dental offices must be in compliance with King County limits when they open.
  • After July 1, 2003: All dental offices must be in compliance with King County limits.


A King County program reimburses some equipment and installation costs: The Voucher Incentive Program sponsored by the King County Hazardous Waste Management Program reimburses qualified businesses for part of the cost of purchasing and installing pollution prevention equipment like amalgam separators. The program reimburses half of what the business spends, up to a total $500 reimbursement per business. To find out how the program works, call 206-263-3038. To request a Voucher Incentive visit from King County staff, call 206-263-3080.


Mercury and silver limits: authority and enforcement

King County limits for metals are required in King County Code--Title 28 and in King County Industrial Waste Local Discharge Limits.

If a business discharges less than 5,000 gallons of wastewater per day, the business must comply only with the instantaneous limits, which are 0.2 ppm for mercury and 3.0 ppm for silver.

King County Code provides that businesses or individuals who illegally discharge substances to the sewer system must pay for damages and may be fined. Names of businesses that are fined are published in a Seattle Times display ad titled "Companies Violate Pretreatment Standards."

 

 

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