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Wastewater Treatment

King County, Washington

For questions about the Wastewater Treatment Division website, please send an e-mail message or contact us at:

King Street Center
201 S. Jackson St., Suite 500
Seattle, WA 98104-3855
Phone: 206-477-5371
Fax: 206-684-1741
Telecommunication device for the deaf (TTY): 711

Get Directions to our office location in Seattle, Washington.

Staff Contacts

Environmental programs

From planning our entire conveyance system to remediating sediment contamination near county outfalls for combined sewer overflows, these programs cover a wide range of services and provide the detailed planning and study necessary to design, build and upgrade our treatment system.

Resource recovery 
Resources from wastewater provide us with healthy crops, renewable energy, green sports fields, lush gardens, robust forests, and vibrant wetlands - all nourished with King County's recycled resources.

Biosolids recycling
King County's program is used as a model throughout the nation and has won many awards for its innovative and environmentally sensitive operations.

Energy recovery 
Information about recovering energy from the wastewater treatment process, including the fuel cell demonstration pilot project.

Reclaimed water 
The Regional Wastewater Services Plan calls for the county to pursue and explore opportunities for expanded water reuse at the county's existing treatment facilities. The policies also call for the county to explore water reuse opportunities at all new treatment facilities.

Technology assessment 
Learn about new technologies, assessment of existing and new wastewater treatment processes, laboratory research, pilot studies and demonstration-scale equipment testing.


  • Combined Sewer Overflow (CSO) Control Program
    Information on what a CSO is, where they are found in the King County system, and ongoing control projects.
  • Conveyance System Improvement (CSI) Program
    This is an array of more than 250 miles of pipes and 42 pump stations that moves wastewater from local communities to the treatment plants. The program focuses on upgrading and improving the existing regional conveyance system as well as planning for future conveyance extensions.
  • Duwamish Waterway Programs
    This portal page describes King County programs to improve water quality and sediments in the Lower Duwamish Waterway.
  • Environmental planning (environmental documents for public review)
    This program ensures that the Wastewater Treatment Division complies with the state and federal Environmental Policy Acts and the federal Endangered Species Act.
  • Green Grants
    Grant funding is available for air or water quality improvement projects, environmental education and community outreach efforts with the the Duwamish River Valley.
  • Industrial Waste Program
    Designed to prevent businesses from discharging substances that can degrade the wastewater treatment process, harm workers or facilities, or affect surface-water quality.
  • Regional Infiltration and Inflow Control Program
    A partnership between the county and the 34 local sewer agencies to study & identify sources of inflow and infiltration into local sewer systems.
  • Sediment Management Program
    Developed in the late 1990s to remediate sediment contamination near county outfalls for combined sewer overflows, or CSOs, in Seattle.
  • Septage Disposal Program
    King County provides septage disposal for commercial haulers at the South Treatment Plant, Renton. The septage facility is open 24 hours/day, 365 days/year.
  • Water Quality Trouble Call Program
    This program supports the Wastewater Treatment Division by responding to water quality emergencies in King County.

Related topics

Seattle skyline

Water quality monitoring data

What can I do?
Tips for conserving and protecting our water resources and sewer systems