A Finite Element Model Of Moisture Flow And Distribution Within A Sanitary Landfill

Abstract

Leachate generation at municipal solid waste facilities has become an increasing public concern, especially in light of numerous documented groundwater and surface water contamination incidents which were directly attributable to nearby landtill sites. Unfortunately, our understanding of the processes involved in the production of contaminated leachate is limited. Landfill excavation studies have indicated a strong correlation exists between refuse moisture content and the amount of degraded refuse, suggesting the amount and distribution of moisture within the landfill are key determinants of leachate formation. Current models of landfill systems are used to estimate total leachate production, however they are limited in their ability to characterize the patterns of moisture distribution within the landfill, partly due to the assumption of homogeneous landfill material properties. Accordingly, a two dimensional finite element computer model, which incorporates the hydraulic properties of various land811 materials, has been developed to examine the effects of anisotropic conditions on moisture distribution patterns within a landfill. The model is based on mathematical expressions of unsaturated flow in porous media. The landtill physical properties input to the model were obtained from test landfill cells constructed and operated by the Delaware Solid Waste Authority (DSWA). The model predicted unique moisture distribution patterns, consistent with the given antecedent rainfall amounts, however it consistently underestimated peak leachate generation measurements. While further investigation is warranted, these results highlight the importance of including various landfill material properties, i.e., hydraulic conductivities, when modeling the moisture flow and distribution within a landtill system.