Beneficial Reuse of Fly Ash as a Replacement for Lime in the Alkaline Stabilization of Biosolids for 'Class A' Exceptional Quality Sludge in Wisconsin

摘要

An existing biosolids lime stabilization process at the City of Kiel, Wisconsin has historicallyused lime as the alkaline material at a rate of about 318 tonnes per year (350 tons per year) and acost of about $34,000 per year. The desire to optimize the operation of the stabilization processled Kiel to pursue the idea of substituting fly ash as the alkaline material in the process. Fly ashfrom a coal-burning electric generating plant about 45 kilometers (28 miles) away was found tobe available free of cost to the City. By way of lab, bench and full-scale testing, fly ash wasfound to be effective in biosolids stabilization and in maintaining “Class A” biosolids status. Thepredicted annual savings to switch from use of lime to fly ash in the stabilization process wasestimated to be $50,000 to $52,000 per year, while increasing the final biosolids volume fordisposal by about 10%.