Long term monitoring of leachate flux into drainage pipes of MSW landfills

Abstract

The measurement of leachate quality and quantity is an essential part of the monitoring of landfills in the different phases during their lifespan. These measurements allow the evaluation of the decomposition processes in the landfill and the efficiency of technical installations for the reduction of the leachate generation. Normally the measurements are made at the outlet of larger sections of the landfill or at the overall landfill. An identification of smaller parts with different biological or hydraulic behaviour within the landfill section is not possible in that case. In the framework of a long-term research project concerning the monitoring of landfills, different devices for small-scale identification of the leachate discharge were developed at the Technical University of Braunschweig. The device allows a measurement of the leachate discharge inside a single drainage pipe having a length up to 375 m. The measurements showed the influence of changes in operation. It was found that the discharge in the pipes and the efficiency of the drainage system was strongly influenced by deformations and torsion of the high-density polyethylene pipes and unequal settlements of the subsoil. The discharge of leachate in the drainage system was, as expected, very non-uniform and in parts the leachate was not flowing inside the pipes, but rather in the surrounding gravel layer. Furthermore, large differences in leachate quality may occur, whereas the differences in discharge volume are small. With the developed system it is possible to control the efficiency and the functioning of top cover systems for landfills.