Sludge-Amended Brick Production: Applicability for Metal-Laden Residues

Studies had shown the feasibility of disposing of sewage sludge by incorporation into bricks. Laboratory experiments were carried out on the fate of metals in this process. Most metals would be trapped within the brick during both firing and weathering as a result of a silicate-based physico-chemical containment mechanism. Volatilization during firing occurred only with selenium, and then only when very high concentrations of the metal were added to the sludge. Simulated weathering at pH 2.5 and 5.0 produced leaching losses for arsenic, selenium and cadmium only marginally above the U.S. EPA extraction procedure limits, and again only when the metal concentrations were very high. Municipal sewage sludge with normal metal concentrations could safely be used in brick manufacture.