Energy Conservation Projects
In pursuing a 15 percent energy reduction goal set by the General Manager, Metropolitan Council Environmental Service (MCES) focused on process efficiency, lighting redesign, and facility recommissioning.
Conservation Studies
In collaboration with Xcel Energy and engineering consultants, MCES completed 26 energy-related studies to identify energy saving opportunities; 40 were identified totaling 46 million kilowatt hours (kWh) or $3 million a year.
Of those 40 identified cost-saving measures:
- 16 have been implemented so far with a total annual savings of 23 million kWh or about $1.4 million per year.
- 24 additional studies are scheduled for 2009.
All Treatment Plants
- Facility recommissioning studies findings (at all plants) implemented in 2008 represent 250,000 kWh saved.
Blue Lake Treatment Plant
- New air diffusers were installed, diffuser density was increased, air leaks were fixed, and isolating valves were installed. This project produced tighter dissolved oxygen control and improved oxygen transfer--saving an estimated 3 million kWh per year.
- Facility recommissioning studies findings (at all plants) implemented in 2008 represent 250,000 kWh saved.
- In construction in 2009: Project to convert energy captured from liquids processing for use in place of fossil natural gas. This saves hundreds of dollars and reduces carbon monoxide emissions. Project is a partnership with New England Fertilizer Company (NEFCO) and received ARRA funding through Minnesota Public Facilities Authority.
- Read general Blue Lake Plant details.
Metropolitan Treatment Plant
- Enhanced maintenance in the aeration process improved the oxygen transfer efficiency. In 2008, half of the aeration tanks were cleaned (see picture, above right), saving 4 million kWh per year. Also, for improved sustainability, a pressure monitoring system was installed to determine when diffusers start going bad.
- Odor control energy improvements made using new packing material. The new material improved scrubber performance to the extent that one of the two scrubber sets could be shut down. This saves 688,000 kWh per year.
- Instrument air compressor modifications were made by changing the load and unload set points, shutting off one unit, and repairing air leaks. This saves 340,000 kWh per year.
- The Liquids Business Unit made several changes in operation which resulted in energy savings of about 3 million kWh per year.
- Facility recommissioning studies findings (at all plants) implemented in 2008 represent 250,000 kWh saved.
- Read general Metro Plant details.
Rosemount Treatment Plant
- In 2008, the Rosemount Plant was decommissioned and the 355 million gallon sewage flow to Rosemount was diverted for processing at the Empire Plant in Empire Township. This saves 1.5 million kWh per year.
Seneca Treatment Plant
- Refurbished secondary aeration system
- New energy efficient HVAC system
- Facility recommissioning studies findings (at all plants) implemented in 2008 represent 250,000 kWh saved.
- Read general Seneca Plant details.