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Vashon Treatment Plant

In addition to award-winning wastewater treatment, operations at the Vashon Treatment Plant support a healthy future in the following ways.

Treatment process

The Vashon Treatment Plant uses oxidation and clarification tanks to treat wastewater. In the oxidation tanks, microorganisms and bacteria eat organic material and contaminants found in wastewater. In the clarification tanks, the solid material settles to the bottom of the tank and leaves the clear water at the top. Solids are cycled back and forth between the oxidation and clarification tanks, meaning most of the solid material is reused to help break down contaminants.

Energy conservation

Saving energy is a key part of King County Executive’s Strategic Climate Action Plan. Vashon Treatment Plant continuously scans the system and implements projects to save energy while maintaining and improving efficiency and performance.

Loop® biosolids

For over 40 years, King County Wastewater Treatment Division has recycled the nutrients in our food back to the land the same way nature does. Loop® is a fertilizer alternative produced by cleaning, recycling, and transforming wastewater into biosolids. We use it on farms and forests to generate healthier, more productive soil that increases crop yields and boosts tree growth. You may see Loop® trucks coming and going from Vashon. Learn about Loop® biosolids here.

Contact us

24 hour emergency and odor reporting:   206-263-1760
Administration:  206-463-7318

9615 S.W. 171st St.
Vashon, WA 98070

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