Bench-scale tests were conducted to evaluate the technical and economic feasibility of the hot acid process for stabilization/conditioning of municipal sewage sludge. This process involves acidification of the sludge (pH 1.5-3) and heating to temperatures below boiling (approximately equal to C). Test results indicate that the process improves the dewaterability of the sludge, destroys essentially all pathogens, and preferentially solubilizes certain heavy metals relative to nitrogen and organics. The process demonstrated the potential for good solubilization and removal of toxic heavy metals including cadmium, zinc, and nickel with minimal solubilization of nitrogen. Thus the hot acid process improves the desirability of sludge solids for land application. A preliminary economic analysis of the process indicates that it is quite cost-competitive with alterntive stabilization/conditioning processes.

Includes bibliographical references (pages 150-152). Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Municipal Environmental Research Laboratory, Cincinnati, Ohio, by Walden Division of Abcor, Inc., and Champion International Corporation, Knightsbridge, under contract no. Contract Number: 68-03-2459.