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.

Comment on our plans for biosolids permitting

We are planning changes to our statewide biosolids permit to streamline permitting for facilities with straightforward permits, allowing us to focus on facilities with more complex needs.

See our notice about the planned changes.

Submit your comments by Jan. 24, 2020.

  • 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