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South Treatment Plant
Find information and facts about South Treatment Plant located in Renton, including the treatment process, capital and improvement projects, and visiting the facility and grounds.
Information on our flooding response, and what to do if your home or business has damage, is on the King County Emergency News blog.
December 2025
Updates
Apply now: Operator-in-Training Program
Only a few days left to apply – don’t miss out on this exciting opportunity!
The Operator-in-Training (OIT) Program is a hands-on, paid training program that can lead to a rewarding career in clean water services.
As an OIT, you’ll play an important role in protecting the health of our communities and the environment. Please note that you must have a high school diploma or GED to apply.
- Apply for the 2026 Operator-in-Training Program - Applications due Monday, December 22, by 11:59 p.m.
- Learn about the OIT Program, including an overview of the program, outcomes, and what to expect if you're selected
- Explore more internship, workforce development, and career opportunities at WTD
From then to now: Celebrating 60 Years of South Treatment Plant
Our latest email update reflects on South Treatment Plant’s 60-year history — from opening in 1965 to the work we do today to protect public health and the environment.
The update also includes highlights from our community engagement at local events this past summer, along with ways you can stay involved year-round.
- Check out the December email update
- Sign up for our email list to stay connected and receive future updates on programs, volunteer opportunities, and events
Aerial view of South Treatment Plant in Renton.
Located in Renton, South Treatment Plant (South Plant) began operating in 1965. South Plant features a 1.5-acre demonstration farm, CitySoil, that produces more than 5,000 pounds of food for a local foodbank. South Plant is our most visited facility, hosting robust on-site educational programming for school groups and plant tours. The facility is also host to a septage disposal facility for commercial haulers. South Plant treats an average of 90 million gallons of wastewater per day from communities in Auburn, Bellevue, Issaquah, Kent, Renton, and Sammamish.
South Plant StoryMap
Are you a wastewater nerd like us? Itching to learn about all the ins and outs of how South Plant operates and benefits the community? We have put together an interactive tool that allows you to do just that.
Visit the South Plant StoryMap to learn about the history of our plant, the workforce that runs it, the way the plant interacts with the community, and more!
Learn more
- See how South Plant's Treatment System works.
- Get the facts on the South Treatment Plant System’s operations here.
- Learn how South Plant contributes to a sustainable future for the surrounding community and environment.
- Explore educational opportunities.