[Testing solid waste leaching/percolation on columns for the characterization of the leachates of a technical landfill discharge] | Tests de lixiviation/percolation en colonnes sur ordures menageres, en vue de la caracterisation des lixiviats d'un centre d'enfouissement technique

Landfilling is still a common way to discharge municipal solid waste. Even if refuse treatment installations have been developed in the recent years such as recycling, composting or incineration, a large amount of residue generated by these treatments is landfilled as final waste. The aim of this study was to measure pollution flux in leachate generated by domestic waste deposits of different composition. Particularly, we intended to follow the evolution of organic matter during different stage of decomposition of wastes. Experimental columns, 0.6 m in diameter and 2 m high, were filled with more or less 120 kg of domestic waste of various composition. The bottom of the column was filled with 10 cm gravel to drain leachates and equipped with a manual gate which allowed leachate evacuation once a week. The refuse was covered with 10 cm sand to spread water over the surface. In order to avoid evaporation and to limit air transfer at the top of the refuse bed, the columns were sealed with a polyethylene cap. The waste studied in this laboratory scale experiment was collected at different stage in a MSW treatment plant in South Belgium. Three different composition of refuse were tested: a rough domestic waste (after shredding), a fraction of shredded refuse which passes though a 50 mm screen and the fraction over 50 mm of the same refuse. Experimental conditions were chosen to be in a good agreement with real conditions in a landfill site, and to allow biological evolution of waste under anacrobic conditions. Temperature was maintained around 35 degrees during all the experience to promote development of mesophilic anaerobic micro-organisms. Water capacity of waste was first fulfilled and then water simulating a net precipitation of more or less 700 mm per year was uniformly distributed on a weekly basis. Leachate has been collected at the bottom of the columns and samples were taken under anaerobic conditions for analysis. The results presented in this paper are relative to acid fermentation stage.