Environmental behaviour of a construction made of a mixture of hydraulic binders and air pollution control residues from municipal solid waste incineration Part 1. Physico-chemical characterisation and modelling of the source term

The reuse of waste materials requires the development of assessment methods for the long-term release of pollutants (source term) from wastes (or mate rials containing wastes) in contact with water. These methods depend on the scenario conditions: characteristics of the materials (especially physical structure and composition), contact with water. The scenario studied here is a water storage reservoir for fire fighting. The reservoir construction is made of a mixture of hydraulic binders and air pollution control (APC) r esidues from a municipal solid waste incinerator (MSWI). The modelling of t he source term is performed in 5 steps ranging from the physico-chemical ch aracterisation of the material to the validation of the proposed model by m eans of field simulation devices. This article presents the first steps of the methodology: physico-chemical characterisation of the source term, iden tification of the main transfer mechanisms and laboratory scale modelling o f the source term. During the physico-chemical characterisation, it has bee n shown that the solidified waste shows a high basic capacity and that a re lative decrease in pH during leaching favours retention of the main polluta nts, During the first leaching sequences, the dynamic leaching tests show t hat the release of pollutants such as cadmium, arsenic, zinc and lead is ex tremely low but that the release of alkaline species (sodium and potassium) and chloride is very high from the beginning, whereas the release of calci um remains very high even after 3600 h of leaching. Identification of the m ain transfer mechanisms concludes that the release of soluble pollutants is the combined result of diffusional transfer of pollutants in the solution and the physico-chemical specificity of the species. The modelling based on these features enables a good simulation of the release but reveals a devi ation from the experimental results after 500 h for alkaline species and 10 00 h for Ca and Cl leaching. However, this deviation only appears after rel ease of the major part of these elements. (C) 2000 Elsevier Science Ltd. Al l rights reserved.