The Metropolitan Council expects to cut an estimated $400,000 annually from its electricity bill for the Metropolitan Water Resource Recovery Facility in Saint Paul, thanks to a project completed in October.
Treating wastewater is an energy-intensive operation. It requires air to be pumped 24/7 into giant aeration tanks where microorganisms help clean up the dirty water. To make the process work, the air must be diffused into tiny bubbles.
The Metro facility’s 16 aeration tanks had a total of 340,000 ceramic diffusers that were reaching the end of their useful lives. We replaced them with more efficient membrane diffusers. The new diffusers will also be much easier to maintain and less expensive to replace, engineer and project manager Mark Lundgren said.
"This upgrade is about more than pipes and treatment facilities—it's about safeguarding our region's future," said Interim Met Council Chair Deb Barber. "Through strategic investments in essential infrastructure, we're honoring our stewardship responsibilities to both current and future generations while ensuring ratepayer dollars deliver maximum value."
The project included several other key components:
- Replacing the 25-year-old system of pipes in the tanks that deliver air to the diffusers
- Creating better access to the aeration tanks, making ongoing maintenance easier
- Rehabilitating the areas under the tanks to better control groundwater levels
- Increasing the number of remotely controlled aeration valves to allow plant operators to more effectively control treatment processes and improve energy efficiency
- Adding backup gates in the final settling tanks to ease maintenance and save costs
The Met Council’s Environmental Services division operates a total of nine water resource recovery facilities in the seven-county region serving 111 communities and about 2.9 million people. The entire system of treatment facilities, regional sewer pipes, lift stations, and metering stations is paid for entirely by user fees.
The 170-acre Metro facility, one of the nation’s largest wastewater facilities, is located on the Mississippi River downstream from Saint Paul. It treats an average of 172 million gallons of wastewater daily from 66 communities in the region.
Wastewater treatment at the Met Council