SEATTLE — The King County Wastewater Treatment Division is piloting a program that will pull heat from the sewer system and use it to heat privately-owned buildings.
It will work with Alexandria Real Estate Equities, Inc., and is looking for two additional property owners to take part.
"It's actually one of the first in the nation where we've been able to have a public-private partnership to allow private property owners to connect into the public sewer infrastructure, to use the heat that's traveling in those pipes underground," Policy and Research Unit Supervisor Erika Kinno said.
The county said the system will pull heat from a sewer pipes, sending it through a heat pump system and more pipes to heat the Alexandria Center for Life Science - South Lake Union campus.
"What you have is a heat exchanger, which is actually very similar to the coils on the back of your refrigerator, and two parallel, closed pipes," Kinno said. "The sewer and the clean water never touch, it's just the heat. The sewage, which is a little cooler, goes back on path its normal way."
The system the county will use has already been tested and used elsewhere, and the county is already heating some of its own WTD properties using this method. The pilot will study how a public-private partnership works. Property managers will pay the county for the use of the energy.
The system is expected to go fully online in 2025.
"We tend to flush and forget, but there's a lot of really valuable commodities that we're flushing down," Kinno said. "We're flushing down water, we're flushing down organic matter, nutrients and heat. Finding ways to recoup those resources and put them to work for the benefit of the community is something King County and the WTD is really committed to."
You can learn more about how the process works at the King County website.