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Sustainability at our treatment plants

Find out how our regional wastewater treatment plants are implementing sustainability practices for our communities and the environment.

We’ve implemented a number of practices at our wastewater treatment plants that demonstrate King County’s commitment to a sustainable and resilient future for our region. For us, sustainability means reusing valuable resources and managing cost-effective operations and capital investments that ensure a healthy natural environment and vibrant communities for everyone. 

In short, we believe that recovering valuable resources goes hand in hand with being a good neighbor.  

Learn about Resource Recovery at WTD and get the facts on exactly how many resources and products our plants are recovering and producing each day.

We recover valuable resources.

Biogas reuse and heat 

During the treatment process, human waste produces a lot of methane gas (or biogas). Biosolids from the solids treatment process are turned into heat and used in various processes at our treatment plants. For example, Brightwater’s Education and Community Center is heated with biogas to keep the facility’s energy footprint low. South Plant sells all its biogas on the renewable market and then purchases natural gas, at a lower cost, to heat its facilities. Those funds then go back into maintaining the wastewater system, capital projects, and equity and social justice work.


Energy conservation 

Saving energy is a key part of the King County Executive’s Strategic Climate Action Plan. As large energy users, our treatment plants are continuously scanning current systems to implement new projects to save energy while maintaining efficiency and performance. Brightwater, in particular, is part of the Wastewater Energy Cohort, which allows for cross-agency collaboration that use best practices to implement innovative process improvements that save energy.


Loop biosolids 

The solids treatment process at our plants produces a nutrient-rich biosolids product called Loop® that is sold to farms and forests as an alternative to chemical fertilizers. It’s used to generate healthier, more productive soil that increases crop yields and boosts tree growth. Loop® can be composted further to create GroCo®, a retail product for home gardens and landscapes. You may see Loop® trucks coming and going from Brightwater and South Plant.


Recycled water 

We recycle water at all of our treatment plants. After being disinfected, recycled water is 99% cleaner than when it came into the plant. At Brightwater and West Point, recycled water is used for industrial uses and irrigation, saving valuable drinking water. South Plant has a partnership with Starfire Sports Complex to provide recycled water that’s used to water their sports fields. Recycled water is also used on-site at South Plant to cool equipment and water grounds, including watering crops at the plant’s own CitySoil Farm. And at Carnation Treatment Plant, recycled water is sent to the nearby Chinook Bend Natural Area for wetland enhancement. 

We are good neighbors.

Natural areas 

Our plants not only clean wastewater, they support the health of the surrounding communities we serve by offering natural areas and other green spaces for the public and wildlife to enjoy. Brightwater features 3 miles of hiking trails, including the North Habitat and Meadow Hill natural areas, which are open from dawn to dusk year-round. In addition, South Plant is host to CitySoil Farm, a 1.5-acre demonstration farm located in a once unused area of the plant grounds. Located next to South Plant is Waterworks Gardens, a public park that also filters and cleans stormwater from the plant’s 50 acres of roads, parking lots, and hard surfaces.


Odor control 

Our treatment plants maintain extensive odor control equipment to ensure that there are no odors beyond the treatment plant fence line. Stinky air is cleaned and scrubbed with carbon pellets that absorb odors and purify it before the air is released. Our high air quality standards and monitoring have allowed our plants to operate continuously without major incidents. We maintain a 24-hour odor control hotline for all our plants and are committed to responding to complaints of bad smells coming from our sewer system promptly and swiftly.

Public art and education

We believe providing different experiences for people to learn about clean water plays an important role in the sustainability of our system and the communities we serve. All our treatment plants incorporate public art in shared spaces per King County’s Public Art Program, managed by 4Culture and funded through the 1% for Art Ordinance. Brightwater, for example, features an extensive public art collection highlighting water and ecology that tells the story of our system’s processes, engaging the public in inquiry and discovery. Our facilities also feature education programs for all ages such as plant tours and volunteer and service learning opportunities that offer a chance for the public to get involved and make a difference.