South Treatment Plant

Welcome to the South Treatment Plant in Renton, Washington.

The plant is part of King County's regional wastewater treatment system that serves more than 1.4 million people and covers 420 square miles in the Puget Sound region. Every day, South Plant cost-effectively treats millions of gallons of wastewater from our homes, offices, schools, agencies, businesses and industries along the east side of Lake Washington from south Snohomish County to north Pierce County.

New. Where to find staff until the new Administration Building is completed in 2009.

History

• In 1958, King County voters created Metro, an agency charged with developing and operating a regional wastewater treatment system.
• The South Plant, a secondary treatment plant, was completed in 1965.
• In 1986, a new effluent discharge pipeline and outfall was completed to eliminate discharges to the Green/Duwamish River and carry treated wastewater 12 miles to a deep-water outfall in Puget Sound.
• In 1994, resulting from a voter approved proposal to merge Metro with King County, King County assumes responsibility for South Plant.
• In 1997, South Plant began producing reclaimed water.
• In 2001, the South Plant was expanded to its current capacity of 115 mgd (million gallons per day) of average wet weather flow and 325 mgd during peak storms.
• South Plant celebrated its 40 year anniversary on Saturday, October 8, 2005.

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The treatment plant in Renton, Washington
(Click image for larger view.)

The Plant

The South Treatment Plant sits on 94 acres in Renton, Washington, south of Seattle. Besides treatment operations, the plant site includes facilities for biosolids handling, water reuse and testing alternative treatment technologies. King County is committed to being a good neighbor with its wastewater treatment facilities and works to ensure safety and minimize impacts of all projects affecting the natural environment, facility neighbors and our employees.

At South Plant, we have devoted extensive effort to odor control, water reclamation, and native landscaping to minimize the impact of the plant on the surrounding community.

Waterworks Gardens opened next to the South Plant in 1996 as a system for incorporating stormwater treatment with public art. With trails, art, native plants, wildlife and ponds, this eight-acre public park naturally cleans all stormwater from South Plant.

During the plant's most recent expansion (completed in 2001), the county embraced the concept of Partnering, which has saved both dollars and time during construction of the new facilities.

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South Plant has been recognized
by the National Association of Clean Water Agencies for excellence in wastewater treatment.

Master Mechanics keep the plant
operating 24 hours a day

The Process

For 40 years, the South Treatment Plant has been providing secondary-level treatment for our region. The average capacity for wet weather flow is 115 million gallons per day. The maximum capacity is 325 million gallons per day during peak storms.

Wastewater coming into the plant undergoes a series of processes, including the following:

• Preliminary treatment: where large debris like rags, paper, and leaves are removed
• Primary treatment: skimming and settling to remove sludge (heavy materials) and scum (lighter materials), which are sent onto the solids handling process
• Secondary treatment: a biological process that consumes suspended and dissolved organic material, leaving the remaining water or secondary effluent at least 85 percent cleaner than when it entered South Plant.
• Disinfection destroys most remaining pathogens, or disease-causing bacteria before the final effluent is released through an outfall pipe and diffuser into Puget Sound.

South Plant's wastewater treatment process produces valuable byproducts that can be reused within the plant and throughout the region, including:

• Biosolids, the nutrient-rich organic matter produced by treating wastewater solids, are used as a soil amendment for dryland and irrigated agriculture, forest fertilization and is composted for landscaping and gardening.
• Reclaimed water -- after disinfection, some secondary effluent undergoes advanced treatment and is reused on site in-plant processes also used off-site for landscape irrigation and to replace drinking water use in industrial processes.
• Energy recovery -- digester gas, or methane is a byproduct of the biosolids digestion process, and is captured, separated, and cleaned, then either sold to Puget Sound Energy or used on-site as an energy source for a cogeneration system and fuel cell to produce electricity and heat for plant use.

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Take an animated tour of the treatment process at South Plant.

Wastewater Treatment Process
How is wastewater treated at King County's South Treatment Plant?
(PDF, 199 KB)

The South Plant discharges treated wastewater under permits issued by the Washington State Department of Ecology.

The reuse facilities, where water gets tertiary (three levels of) treatment, before being used for irrigation at the plant and Fort Dent Park.

King County contracts with a local private company (GroCo, Inc.) to make a biosolids compost which is marketed in the Greater Seattle area as GroCo . More about Biosolids Compost.

The People

Thanks to nearly 140 dedicated employees, the South Plant treatment system runs 24 hours a day, seven days a week. Trained professionals – operators, lab technicians, maintenance crew members, process control personnel and administrative staff – ensure the South Plant and the pipelines and pump stations that supply it with wastewater operate effectively.

Operators, licensed by the state, are responsible for the daily operations; lab staff perform analysis of the plant processes and products; process control staff analyze the data to optimize the plant's operation; and crews of machinist, mechanics, and electrical and instrumentation staff maintain and repair equipment at the plant and at the conveyance facilities in the service area.

Our goal is to provide the region with the best wastewater treatment service available while operating as efficiently and effectively as possible.

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Address and Contacts

Administration: 206-684-2400
Control Room and Odor Control Hotline:
206-684-2404
     24 hours a day

1200 Monster Road S.W.,
Renton, WA 98057
Fax: 206-684-2448

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More about the South Treatment Plant

Links to .pdf files require the free Adobe Acrobat Reader to view.

  Plant Tours

  South Plant Newsletters

• Spring 2008
• Summer 2007
• Fall 2006
• Summer 2005

  Fuel Cell Demonstration Project at South Plant.

  The Maintenance Team Report (PDF, 1.1 MB)

This report describes the roles, responsibilities and recent accomplishments of the maintenance teams at the West Point plant and South Plant in Renton.

  You can also find out about the following:

• The West Point Plant in Seattle
• Biosolids recycling and application
• Odor control in wastewater facilities
• Brightwater, a third regional treatment plant under construction
• Public involvement and community relations
• King County Wastewater (NPDES) Permits
• Speakers Bureau

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For questions about the Wastewater Treatment Division Web site, please send an e-mail message. For general information about the division, contact us at:

Department of Natural Resources and Parks
Wastewater Treatment Division
201 S. Jackson St., Suite 505
Seattle, WA 98104-3855
Phone: 206-684-1280
Fax: 206-684-1741
Telecommunication device for the deaf (TTY): 711

Updated: May 6, 2008