System Dynamics Simulation of Selected Composite Landfill Liners for Leachate Containment

The disposal of wastes through landfiling is becoming increasingly acceptable worldwide. Its attendant leachate pollution is however a source of concern to the 21 st century environmental engineering researchers. This paper therefore focuses on the application of system dynamics modeling technique in simulating the breakthrough times of selected composite liners in order to determine their effectiveness in leachate containment. Four (4) composite liners were studied viz: High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE); Geotextile and Geonet; Geosynthetic Clay Liner (GCL) and Compacted Clay Liner (CCL); and Silt and Sand. Governing equations coded in Visual Basic computer programming language based on the principles of system dynamics modeling was applied in the determination of retention abilities of the selected liners. Notable properties of the liners like Hydraulic Conductivity, Permeability, Porosity and Hydraulic Head were employed in model validation. Other inputs include the Thickness, Placement Slope and Insertion Depth of the liners. The interrelationship of the properties and breakthrough times was determined through simulation processes using STELLA 9.1.4 software.of the composite liners studied, HDPE-LDPE combination was found to be the most effective with the longest breakthrough time. The Geotextile-Geonet combination however has the highest leakage rate. The study therefore recommends the use HDPE-LDPE liner combination for use in landfill leachate retention. Keywords: system dynamics, leachate, landfill, composite liner, breakthrough time