Combined Heat and Power Partnership
Municipal Wastewater Treatment Facilities
- Opportunities for Combined Heat and Power at Wastewater Treatment Facilities: Market Analysis and Lessons from the Field (PDF) (57 pp, 1.2MB, About PDF) presents the technical and economic potential of CHP at WWTFs and operational insights associated with CHP at WWTFs obtained through interviews conducted by the Partnership.
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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 fuel to generate reliable electricity and heat 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 a 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 purchased fuels for thermal needs.
- May qualify as a renewable fuel source under state renewable portfolio standards and utility green power programs.
- Enhances power reliability for the plant.
- Produces more useful energy than if the WWTF were to use biogas solely to meet digester heat loads.
- Reduces emissions of greenhouse gases and other air pollutants, primarily by displacing utility grid power.
EPA conducted an analysis of the technical and economic potential for CHP at WWTFs titled Opportunites for Combined Heat and Power at Wastewater Treatment Facilities: Market Analysis and Lessons from the Field (PDF) (57 pp, 1.2MB, About PDF) This market and technical analysis found that CHP is a strong technical fit for many WWTFs. Moreover, it can be a compelling investment at WWTFs, depending on local electricity prices. While many WWTFs have already adopted CHP, substantial opportunities remain.
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.
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, About PDF) - 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 (PDF) (8 pp, 200K, About PDF) - 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, About PDF) - 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.
- Columbia Boulevard Wastewater Treatment Plant (Portland, Oregon): 320 kW Fuel Cell and Microturbine Power Plants (PDF) (5 pp, 532K, About PDF) - 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.
- Evaluation of Combined Heat and Power Technologies for Wastewater Facilities - This interim report serves as a planning-level tool for wastewater professionals and provides an examination of commonly used and emerging combined heat and power (CHP) technologies for converting anaerobic digester gas to electrical power and process heat. The report was developed by Columbus Water Works, under an assistance agreement awarded by EPA in support of their Columbus Biosolids Flow-Through Thermophilic Treatment (CBFT3) National Demonstration Project. It provides detailed technical information about existing technologies for producing heat and power from biogas including: internal combustion engines, gas turbines, microturbines, and fuel cells as well as other beneficial uses for digester gas. The report includes detailed process descriptions and performance and cost data. It also addresses factors such as infrastructure requirements, digester gas treatment, and operational issues. The interim report includes four in-depth facility case studies from across the country that demonstrate successful biogas-to-energy projects.
- 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.