Mercury Behavior in a Wastewater Sludge Incineration Process

by Dianne Dorland, Univ of Minnesota, Duluth, United States,
Joseph J. Stepun, Univ of Minnesota, Duluth, United States,



Document Type: Proceeding Paper

Part of: Water Quality Issues at Fossil Fuel Plants

Abstract:

The Western Lake Superior Sanitary District (WLSSD) in Duluth, Minnesota utilizes solid waste as fuel to incinerate wastewater treatment sludge, conserving energy resources while reducing landfill loading requirements. The wastewater treatment sludge is incinerated with refuse derived fuel (RDF) in a fluidized bed reactor. A preliminary evaluation of the process flows and compositions in the plant was used to determine overall and mass balances and streams with high metal concentrations. Mass balance calculations indicated that approximately 50% of the total mercury left the process in the gas stream and approximately 50% was contained in the wastewater effluent at a concentration of 100-400 ng/L. The principal form of mercury in the stack gas appears to be elemental mercury. In the wastewater effluent, mercury appears to be complexed as the Hg⁺² cation. This paper presents a process description, laboratory testing results, and the outcome of initial plant trials for mercury removal.

Subject Headings: Mercury (chemical) | Incineration | Sludge | Wastewater management | Wastewater treatment | Industrial wastes | Water treatment | Lake Superior | Great Lakes | Minnesota | United States

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