A flow-through leaching model for monolithic chemically stabilized/solidified hazardous waste

Cement-based stabilization/solidification is a technology that is being used for the treatment of hazardous wastes before they are land disposed. It involves adding one or more solidification reagents to a waste stream and turning it into a monolithic solid. The resulting solidified waste products usually have improved handling characteristics, lower permeability and, hence, the leaching of contaminants from the waste can be reduced. Leaching occurs when a leachant contacts a waste and carries away contaminants from the waste. In this paper, the common leaching test methods for the evaluation of solidified/stabilized wastes and the leaching models that have been applied are reviewed. This paper also introduces a new model for the prediction of the long-term leaching behavior of cement-based stabilized/solidified hazardous wastes in a flow-through leaching test environment. The flow-through leaching environment, which is based on flexible wall permeameter test equipment, is different from other leaching test methods since the leaching occurs under a combination of diffusion and dispersion actions. The assumptions and limitations in applying the new model are highlighted.