Phosphate and Thermal Stabilization of Dredged Sediments for Reuse as Construction Material

Rivers including the Passaic and Hackensack and the associated New York/New Jersey Harbor Estuary are dredged regularly as part of maintaining navigable harbors and waterways. The dredged sediments are often contaminated with both organic and inorganic toxins and their disposal is therefore potentially expensive. If effectively stabilized, however, sediments have potential for beneficial reuse in the construction industry as an alternative to disposal. The focus of this study is on the metal contaminants, where phosphate addition and thermal treatment at 700oC are applied to stabilize metal contaminated sediments by forming sparingly soluble phases such as hydroxylapatites. Organics are mineralized with the off-gas treated through carbon adsorption. The effectiveness of stabilizing metal contaminants will be assessed using a suite of complementary analyses including the U.S. EPA toxicity characteristic leaching procedure (TCLP), on both raw and treated sediments. The TCLP results will be validated by examining the metal speciation at the molecular level using x-ray atomic spectroscopy (XAS) along with x-ray diffraction (XRD) and sequential chemical extraction.