We regulate the wastewater treatment plants that produce biosolids and the businesses that apply biosolids for farmers, including how this material is treated, tested, and used.

Biosolids are a product of wastewater treatment systems. Rich in organic material and nutrients, biosolids are used by farmers across Washington to grow a variety of crops like wheat, corn, grass hay, and hops. Proper oversight, testing, and application ensures biosolids benefit farmers and soil without leaching nutrients into surface or groundwater.

2020: New statewide general biosolids permit in development

The current statewide general biosolids permit in Washington expires on Sept. 4, 2020. We will issue a new statewide permit that takes effect after that.​

See our preliminary notice about the planned changes.

We will propose a new statewide general biosolids permit. With this new general permit, we are aiming to streamline permitting for facilities with straightforward requirements, which will allow us to focus on facilities with more complex needs.

To be added to our list of interested parties, please contact:

  • Email
  • Mail:
    • Emily Kijowski
      Department of Ecology, Solid Waste Management
      P.O. Box 47600, Olympia, WA 98504-7600

Learn about biosolids

  • Research on biosolids
  • How wastewater treatment plants make biosolids
  • Pollutants and pathogens in biosolids
  • Biosolids use in Washington

Permitting and forms

Biosolids laws and rules