Time progress of the quality of a solid

Leaching by percolation waters of toxic pollutants from solid wastes in a landfill occurs in a substantially different way to that suggested by elution tests in batch agitated reactors. Effective release, in fact, is influenced by two important aspects that distinguish it from the reference standard: gradual removal of the pollutant and hence a possible change in the matrix; the chemical and physical characteristics of the percolation liquid itself, as determined by the acid or basic nature of the wastes. The composition of the percolate from an industrial waste landfill was evaluated to determine the validity of these general considerations. It was found interesting to correlate the composition of the wastes with the transfer of metals and organic substances to the percolating liquids, this being derived from both the flow of rainwater and the expulsion of interstitial liquid present in the wastes. The discrepancy between the real washout and its simulation by a laboratory test was also confirmed. From a practical standpoint, some conclusions are drawn with regard to disposal of the percolate and its treatability, these being primarily important in the case of organic substances (COD and mineral oils).