Partnership with dental offices reduces mercury in wastewater

Date: Tuesday, February 14, 2023

For two centuries, dentists successfully used amalgam — a mixture of liquid mercury and a powdered alloy — to fill dental cavities. For the past 20 years, the Met Council has partnered with the Minnesota Dental Association (MDA) on a voluntary Amalgam Recovery Program for dental offices in the regional wastewater system service area (PDF). The goal is to minimize the release of amalgam’s potent neurotoxins into the environment.

It’s been a successful partnership. This partnership incentivized dental clinics in Met Council’s service area to install amalgam separators — devices that take amalgam out of the wastewater stream before it leaves a facility — with a minimal removal efficiency of 99%.

Met Council will issue general permits to dental clinics

In 2017, EPA’s dental rule went into effect, which made it mandatory for all general practice and endodontic dental clinics to install an amalgam separator with a mercury removal efficiency of at least 95%. Because separators are now mandatory across the nation, the Met Council recently approved the implementation of a general permit requiring the proper installation, operation, and maintenance of amalgam separators at general practice and endodontic dental clinics.

Even though nearly all the 850+ regional general practice and endodontic dental offices already participate in the Amalgam Recovery Program, about 20% do not submit their annual compliance report on time, which incurs significant administrative costs for the Met Council.

“Most of the burden has been getting dental clinics to submit their compliance statements on time,” said Tina Nelson, manager of industrial waste and pollution prevention for Metropolitan Council Environmental Services. “By transitioning to a general permit, we have more enforcement authority to ensure reports are submitted and we minimize our administrative costs.”

Amalgam Recovery Program significantly reduces mercury levels in wastewater

Dental wastewater may be contaminated with mercury whenever dentists work on teeth containing mercury amalgam fillings, even if the dentist is not placing new mercury amalgam fillings themselves.

To date, we have measured a 67% reduction in the amount of mercury entering the massive Metropolitan Wastewater Treatment Plant in Saint Paul.

General permit to include best management practices

Over the years, the Met Council has developed several general permits for different industry sectors to implement best management practices while reducing the regulatory burden. The new general permit for dental offices will include best management practices (PDF), a resource to help the clinics manage their wastes, operate and maintain their amalgam separator equipment, and ensure that they remain in compliance.

Posted In: Wastewater & Water