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Many wastewater treatment plants use the gas produced by the anaerobic digestion process (i.e., digester gas) to fuel onsite combustion sources, such as boilers or engines. The combustion process results in emissions of a number of contaminants, including volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). These VOC and HAP emissions are potentially primary contributors to the facility-wide emissions. In addition, many state agencies have air toxic regulations that require a facility to address the community health risk associated with individual VOC and HAP emissions. However, speciated VOC and HAP emission factors from the combustion of digester gas are not readily available.

A major upgrade at a large municipal wastewater treatment plant in the northeast included the installation of boilers that would combust the digester gas produced at the plant supplemented by natural gas as needed. The environmental review process required that speciated VOC and HAP emissions from digester gas and natural gas-fired boilers be developed for use in a dispersion modeling analysis to predict the potential air toxic impacts associated with the plant upgrade. Based on an initial search of available VOC and HAP emission factors from gas-fired boilers, it was found that USEPA provided emission factors for natural gas-fired units, but did not provide emission factors for digester gas-fired combustion units. Therefore, an extensive literature search was performed to locate VOC and HAPs emissions from digester and natural gas-fired boilers.

This paper will discuss the methodology used to compile the extensive VOC and HAP emission factors database for the gas-fired boilers, and present a summary of the database. Sources included USEPA, the Gas Research Institute (GRI), source sampling data from various wastewater treatment facilities, and other published documents, such as the Pooled Emission Estimation Program (PEEP) reports. The emission factors collected were screened and statistically evaluated for inclusion into the database. The final database was then used to estimate emissions from the gas-fired boilers at the facility.

Document Type: Research Article


Publication date: 2004-01-01

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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