Comprehensive Emission Testing for Low Level Toxics Conducted at a Municipal Sludge Incinerator Facility

Recent changes to Wisconsin's air toxics regulation, NR 445, and the need to develop site specific emissions factors and defined operating parameters prompted the Green Bay Metropolitan Sewerage District to conduct comprehensive emission tests for the two multiple hearth incinerators operated at their 50 MGD wastewater treatment plant. In addition to criteria pollutants, GBMSD tested for eight dioxin, nine furan, and twelve PCB congeners; fifteen metals; three hydrogen halides; chlorine; and five organic compounds that are considered to be by-products of combustion. Emissions from each incinerator are controlled with a Venturi/Impingement scrubber.Because pollutant formation may be influenced by combustion and/or post combustion temperatures, the two incinerators were tested at different solids loading rates (one test at a “maximum” rate and one test at a “typical” rate) resulting in two different temperature profiles due to the location of the combustion zone in the incinerators.Significant efforts were taken to ensure the detection limits from the dioxin, furan, and PCB analysis would be low enough to accurately assess compliance with applicable State of Wisconsin emission limitations.Several publications present emission factors from multiple hearth incinerators operating with municipal wastewater biosolids including USEPA's Compilation of Air Pollution Emission Factors (AP-42), the FIRE Database, and An Inventory of Sources and Releases of Dioxin-Like Compounds in the United States for the Years 1987, 1995, and 2000 published in November 2006. A comparison of the results of the GBMSD testing with these published values will be provided.