Skip to main content

Planning ahead to treat wastewater

By January 24, 2022June 13th, 2023No Comments

We have some of the largest wastewater treatment plants in the country. It takes a decade or more to build large wastewater projects, so it’s important we plan ahead. That’s where our planning staff and programs come in.

Recently, we launched a new program for planning around our treatment plants called Treatment Planning. Through this program, our staff identify and plan for what we will need to clean water and recover resources at our treatment plants – including policies, capital projects, and funding.

Most of King County’s wastewater flows to three regional treatment plants (BrightwaterSouth, and West Point) where the wastewater flows through a series of treatment processes that remove waste from the water and protect public health and the environment. In addition, there are two local treatment plants (CarnationVashon) that serve smaller communities within the our service area. 

Connecting treatment planning to other planning

We have different programs that develop long-range plans for the entire regional sewer system, like the Combined Sewer Overflow Program, the Conveyance System Improvement Program, and now the new Treatment Planning Program. One way to think of it: Our programs within our utility are like trees that make up a forest. Some trees grow close to each other and have intertwined branches, and some are on the edge of the forest and look a little different. But how do the trees stay connected and still see the bigger picture (the forest)? The Treatment Planning Program can help us understand how our treatment plants are connected with the rest of our utility’s work, so that our agency can create strategic, long-term plans with the entire organization (the forest) in mind.

A trail goes thru a conifer forest, the sun shining thru the trees
Dockton Forest, Image courtesy of King County Parks

How much can we treat at different steps in the process?

In 2019, we completed a study on the capacity of our treatment plants, called the Treatment Plant Flows and Loadings Study. The study identified upcoming capacity constraints for each major step in the treatment process (primary treatment, secondary treatment, solids treatment, and resource recovery) at our three regional treatment plants over the near term (10 years) to long term (20+ years).

Depending on the process we’re looking at, capacity can mean something slightly different for each one. But in general, it means how much the treatment plant can process without a negative impact to the other steps or quality of our water or biosolids. The Treatment Planning Program works with staff across our utility to understand what it will take to keep our treatment plants running efficiently, and then plan for it.

A graphic that shows the capacity limitations over time from the 2019 Treatment Plant Flow and Loadings Study
Identified capacity limitations from the 2019 Treatment Plant Flow and Loadings Study, as of Dec 2019

Are there regulations we have to plan ahead for?

In addition to making sure we have enough capacity in treatment processes, each treatment plant must meet regulatory permits and potential new regulations. That may require additional planning, staffing, operational changes, technology improvements, and larger-scale projects. This planning program works to see the forest and the trees, the big picture and the details, and share information across our agency. We can take information from all parts of our utility, from large system-wide planning efforts to day-to-day input from staff and connect it all together. That way, we can make integrated, informed, and strategic decisions.

A graphic with trees that shows how the Treatment Planning Program intersects with other parts of our utility's business
How the Treatment Planning Program intersects with other parts of our utility’s business

For more information, check out our website: