Modeling of municipal waste landfill leachate dispersion with finite element modeling approach using COMSOL software

Leachate from waste disposal is recognized as one of the primary sources of groundwater contamination. Therefore, improving the management of landfill sites is crucial for reducing and controlling environmental threats. This study focuses on modeling the dispersion of leachate in a landfill in the city of Isfahan using the finite element method, located 35 kilometers outside the city. The leachate is considered in this area with dimensions of 100 by 250 meters and a depth of 2 centimeters from the bottom. The transmission and spread of pollution across twenty sub-layers of soil have been modeled using Richards' equations and pollution transport equations in porous media. This research utilizes COMSOL software to merge different environments using two model equations, and the three-dimensional model investigates the movement and absorption of leachate based on these equations. Meshing in the landfill is done finer in the upper and bottom layers where leachate leakage exists and coarser in the lower parts. Also, mesh modeling in the software is done freely and in a hexagonal shape. According to the findings, the soil under the landfill becomes saturated over time, with the saturation occurring faster in the upper layers. Modeling results show that phosphorus metal pollution has penetrated up to a depth of 1.8 meters in the soil over 15 years, and leachate has reached approximately 10 meters deep into the ground. Given the proximity of groundwater to the soil surface, measures such as pumping wells and geomembranes must be considered to prevent pollution from entering the groundwater.