Dental wastewater discharges

Amalgam separator compliance

An amalgam separator takes the mercury and other pollutants out of the water that goes down the drain in the dentist’s office. This way both the pollutants and the water can be treated properly to protect the environment.

Most dental offices in King County's compliance area have approved amalgam separator units. Dental offices, including endodontists and some pediatric specialties, are required by EPA regulations (40 CFR Part 441) to submit a one-time compliance report.

The following specialty dentist offices do not need to fill out a compliance form:

• Oral pathology
• Oral and maxillofacial radiology and surgery
• Orthodontics
• Periodontics
• Prosthodontics dentists using a mobile unit

King County Industrial Waste compliance area

Enter your business' address, including the city, into the search box to determine if your dental practice is in the compliance area.

What you can expect at a dental office inspection

King County Industrial Waste (KCIW) conducts compliance inspections of dental practices that discharge mercury into the King County sewage system. Inspections normally take less than thirty minutes.

During a compliance inspection, the inspector will verify that:

• The dental office has installed an approved amalgam separator unit or has a valid wastewater discharge permit.
• The dental office is properly maintaining the amalgam separator, review maintenance records.
• The dental office has submitted a one-time compliance report to King County Industrial Waste Program. The dental office should have a copy of the completed one-time compliance report available for review during a compliance inspection.
• The dental office is following the two BMPs as specified in Section 441.30(b) or Section 441.40 and will continue to do so:
  • Waste amalgam including, but not limited to, dental amalgam from chair-side traps, screens, vacuum pump filters, dental tools, cuspidors, or collection devices, must not be discharged to a publicly owned treatment works (e.g., municipal sewage system).
  • Dental unit water lines, chair-side traps, and vacuum lines that discharge amalgam process wastewater to a publicly owned treatment works (e.g., municipal sewage system) must not be cleaned with oxidizing or acidic cleaners, including but not limited to bleach, chlorine, iodine and peroxide that have a pH lower than 6 or greater than 8 (i.e. cleaners that may increase the dissolution of mercury).

Additionally, the inspector will:

• Check that x-ray fixer, chemical solutions, disinfectants, and cold sterilants are properly managed.
• Review records, such as receipts for equipment and waste removal. Find more information in the Best Management Practices for Dental Office Waste (775KB).

Inspection follow-up

KCIW follows up with offices that do not practice the minimum Best Management Practices or who do not have the required paperwork. A typical inspection follow-up includes the completion of an inspection report and an evaluation of the practice's compliance. If the practice is in compliance, no further action is needed. 

An inspector will set up a compliance schedule if major problems are noted during the inspection. If problems are not corrected, King County may proceed using its Enforcement Response Plan.

Why are dental wastewater discharge regulations important?

One of the best indicators of the quality of King County wastewater discharges is the condition of our Loop biosolids, the nutrient-rich fertilizer alternative and natural soil builder created from King County’s wastewater. Loop contains low levels of metals and organic chemicals. These low amounts are thanks to the cooperation our businesses and industries. 

KCIW inspects a portion of the dental offices each year. We monitor that offices have put the required best management practices into effect. The program will continue to track mercury levels in Loop.

Mercury levels in King County Loop biosolids

Efforts to remove mercury from wastewater is one way we are ensuring Loop is high quality. Ninety-five percent of King County dental offices have taken steps to reduce the amounts of mercury and silver discharged to the sewer system. Most offices have installed amalgam separators and followed the best management practices. This effort has contributed to more than a fifty percent reduction in the mercury levels in Loop since 2001.

King County uses 100% of Loop beneficially to improve soils, store carbon, and grow plants on farms and forests.