Fractionation of the organic matter contained in leachate resulting from two modes of landfilling: An indicator of waste degradation

Three experimental pilots were set up at the semi-industrial scale to assess the impact of leachate recirculation and Mechanical Biological Pre-treatment (MBP) before landfilling on the biological degradation of landfilled wastes. The organic matter contained in leachates resulting from these pilots has been used as an indicator of waste degradation. Fractionations were carried out (i) using XAD resins in order to divide the organic matter into several fractions according to the hydrophobic character of the molecules and (ii) using an ultrafiltration protocol to divide the organic matter into several fractions according to the apparent molecular weight of molecules. Three phases of degradation are determined according to the distribution of the organic matter and according to the humification rate. The humification process seems to be more rapid for MBP leachates than for Bioreactor leachate. These results were confirmed by the ultrafiltration results indicating that, to date, MBP leachates contain more molecules with a high molecular weight than Bioreactor leachate. However, this could be explained by an interruption of waste degradation due to an accumulation of volatile fatty acids. (C) 2007 Elsevier B.V All rights reserved.