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For more information about the Biosolids Recycling Program, please send us an email message or contact us at: 

King County Wastewater Treatment Division
Resource Recovery
201 S. Jackson Street
Mail Stop: KSC-NR-0512
Seattle, WA 98104
Phone: 206-684-1247
Fax: 206-684-2057

Biosolids Quality

King County strives to produce the highest quality biosolids economically and practically achievable. To ensure the quality and safety of biosolids, the physical, chemical and microbial characteristics are regularly monitored.

Biosolids samples are analyzed for nutrients, trace metals, trace organic pollutants and microbes, providing information on the physical, chemical and microbial characteristics of biosolids. King County analyzes biosolids monthly in order to characterize quality, examine changes over time, determine biosolids land application rates and to comply with national and state regulations for biosolids recycling.

Biosolids quality
More than two decades of improvements in the pretreatment of the County's industrial wastewater.

Since the early 1980's, King County's industrial waste source control and pretreatment program has significantly reduced the amount of trace metals and other pollutants entering the treatment system. Biosolids quality has greatly improved due to source control efforts combined with City of Seattle's efforts to reduce metals from corrosion of water pipes, and the gradual elimination of leaded gasoline. The Local Hazardous Waste Management Program provides education, collection and technical assistance to small businesses and citizens on proper handling of materials which could pose a threat to wastewater and biosolids quality.

Continual improvement

Biosolids from King County have been recycled in Washington for more than 30 years. The farmers and homeowners who use biosolids products rely on King County's commitment to producing a high quality product. Here is what we do to maintain the quality of our biosolids and ensure its proper use and safety:

  • Work with citizens and local businesses to reduce contaminants in wastewater.
  • Treat wastewater thoroughly to protect public health.
  • Follow the advice of university scientists.
  • Abide by all local, state and federal laws.
  • Operate under an Environmental Management System (EMS). King County is one of the first wastewater utilities in the nation that have an EMS for biosolids. The EMS covers each step in biosolids production, from pretreatment to proper management land application sites. This ensures that we work together to produce the best product possible and strive for continuous improvement in all facets of our job.

What can you do to protect biosolids quality?

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  • Throw stickers from fruit and vegetables in the garbage, not down the sink.
  • Dispose of plastics, including feminine hygiene products and condoms, in the garbage.
  • Return unwanted or expired prescription and over-the-counter drugs to drug "take-back programs" or leave them in the original container and place the container in a closed heavy-duty ziplock bag. Place this bag in another plastic bag (so not conspicuous) and throw it in the garbage.
  • Dispose of kitchen grease in the garbage, not down the sink
  • Choose biodegradable non-toxic cleaning supplies

For more information about disposal alternatives, as well as safe alternatives to toxic household chemicals, visit http://www.lhwmp.org.

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