Municipal Wastewater Treatment Facilities

Strategic Markets

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Key Resources

The Energy Savings and Energy Reliability for Wastewater Treatment Facilities Fact Sheet summarizes the technical and economic benefits of using biogas-fueled CHP from an anaerobic digester at a wastewater treatment facility and provides engineering rules of thumb for considering potential electricity and thermal outputs. Download a PDF version (4 pp, 206K) to print and share.
The Opportunities for and Benefits of Combined Heat and Power at Wastewater Treatment Facilities (PDF) (46 pp, 647K) highlights the benefits of CHP and provides engineering rules of thumb when considering CHP systems at a municipal wastewater treatment facility.

The CHP Partnership presented the New York Power Authority Fuel Cell Project with a 2004 CHP Certificate of Recognition (PDF) (39 pp, 1MB), recognizing the pollution reduction, energy efficiency, and innovative qualities of its fuel cell CHP project installations at four municipal wastewater treatment plants in New York state.

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Combined heat and power (CHP) is a reliable, cost-effective option for municipal wastewater treatment facilities (WWTF) — also known as Publicly Owned Treatment Works or POTWs — that have, or are planning to install, anaerobic digesters. Biogas flow from these digesters can be used in a CHP system as "free" fuel to generate reliable electricity and power for the WWTF.

WWTFs are critical for maintaining public sanitation and a healthy environment, and must be able to operate in the event of a natural or man-made disaster, as well as any utility power outage. Because of its ability to produce electricity and heat on site, independently from the grid, CHP is a valuable infrastructure addition for WWTFs.

A well-designed CHP system that is powered by digester gas offers many benefits for WWTFs because it:

Produces power at a cost below retail electricity.
Displaces fuels normally purchased for the facility's thermal needs.
Qualifies as a renewable fuel for green power programs.
Offers an opportunity to reduce greenhouse gas and other air pollution emissions.
Enhances power reliability for the treatment plant.

The CHP Partnership conducted an analysis of the technical and economic Opportunities for and Benefits of CHP at Wastewater Treatment Facilities (PDF) (46 pp, 647K). The study found significant potential already exists for (1) generating electricity and thermal energy, and (2) reducing greenhouse gas emissions at facilities that currently have anaerobic digesters.

More than 500 large WWTFs (with influent flow rates greater than 5 million gallons per day [MGD]) around the country use anaerobic digesters to process their waste—thereby producing biogas. If all of these facilities used their biogas to fuel CHP, they would generate an additional 340 megawatts (MW) of clean electricity each year. This increase in CHP use would eliminate approximately 2.3 million metric tons of carbon dioxide annually—equivalent to removing the emissions of almost 430,000 cars or planting nearly 640,000 acres of forest.

In general, a WWTF with a total influent flow rate of 4.5 MGD can produce approximately:

100 kilowatts (kW) of electricity to offset purchased electricity or sell to the grid.
12.5 million British thermal units (Btus) per day of thermal energy that can be used as heat for an anaerobic digester and/or for space heating loads.

In states where electricity prices are low, burning biogas directly in boilers might be the most economical investment for a WWTF.

Additional Resources

The CHP Partnership collaborates with other government and nongovernmental agencies and programs that are interested in promoting the benefits of CHP for WWTFs. The following resources provide further insights and examples of WWTFs benefiting from the use of CHP, along with organizations that could provide additional information.

Case Studies

Numerous municipal wastewater treatment facilities have successfully incorporated CHP systems into their operations, employing a variety of technologies and biogas utilization options. The following case studies demonstrate the benefits and operational characteristics of CHP systems at various WWTFs.

Maintenance Helps Million Hour Engines Thrive at Tucson, Arizona, Wastewater Cogeneration Plant (PDF) (3 pp, 382K) - The Ina Road WWTF treats approximately 35 MGD of wastewater. The facility uses six internal combustion engines to generate approximately 2.5 MW of electricity and thermal energy that is used for hot water; chilled water; heating, ventilation, and cooling (HVAC); and to run the anaerobic digesters. By utilizing biogas, the facility pays no more than $0.05/kilowatt-hour (kWh), which compares very favorably with the local average of $0.08 to $0.11/kWh.
King County (Washington) Fuel Cell Demonstration Project - In 2003, King County's South WWTF installed a 1 MW molten carbonate fuel cell demonstration project that generates electricity and thermal energy for onsite needs.
Essex Junction (Vermont) WWTF: 60 kW CHP Application (PDF) (2 pp, 191K) - The Essex Junction WWTF uses two 30 kW microturbines to generate electricity and thermal energy. The CHP system's operational efficiency is 80 percent and produces annual energy savings of 412,000 kWh (36 percent of the facility's electricity demand). The project was installed in 2003 and has an estimated payback of seven years.
Albert Lea (Minnesota) WWTF: 120 kW CHP Application (PDF) (2 pp, 175K) - The Albert Lea WWTF uses four 30 kW microturbines to generate 120 kW of electricity and 28 million Btus of thermal energy per year, which is used for space heating and to heat the facility's anaerobic digesters. The CHP system was installed in 2003 and has an estimated payback of four to six years.
Columbia Boulevard Wastewater Treatment Plant (Portland, Oregon): 320 kW Fuel Cell and Microturbine Power Plants (PDF) (5 pp, 532K) - The Columbia Boulevard WWTF uses a 200 kW CHP system to produce electricity and thermal energy for the facility. A primary motivation for the CHP system was to provide backup power for the facility after it experienced several extended power outages during the mid-1990s. The CHP system was financed by tax dollars, as well as multiple national, state, and utility grants.

Wastewater Treatment Resources and Organizations

The following organizations work closely with the wastewater treatment industry and offer a wealth of knowledge concerning wastewater treatment and the use of anaerobic digestion.

EPA Office of Wastewater Management (OWM) - OWM oversees a range of programs contributing to the well-being of the nation's waters and watersheds.
National Association of Clean Water Agencies (NACWA) - NACWA represents the interests of more than 300 public agencies and organizations. NACWA members serve the majority of the sewered population in the United States and collectively treat and reclaim more than 18 billion gallons of wastewater daily.
Water Environment Federation (WEF) - Founded in 1928, WEF is a not-for-profit technical and educational organization with members from varied disciplines who work toward the organization's vision of preservation and enhancement of the global water environment.
Water Environment Research Foundation (WERF) - WERF helps improve the water environment and protect human health by providing sound, reliable science and innovative, effective, cost-saving technologies for improved management of water resources.
Air & Waste Management Association (A&WMA) - A&WMA is a nonprofit, nonpartisan professional organization that provides training, information, and networking opportunities to thousands of environmental professionals in 65 countries.

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