Modeling of leachate organic migration and attenuation in groundwaters below sanitary landfills

A model for predicting the concentrations of leachate organics, measured as chemical oxygen demand, in groundwaters below sanitary landfill sites is developed. Simultaneous Michaelis‐Menten substrate utilization and microbial mass production equations, with convection and dispersion included for the former, were used for the modeling of biodegradation. For substrate concentrations significantly less than the half utilization rate coefficient and for microbial populations approaching a steady state the Michaelis‐Menten equations are reduced to a first‐order reaction kinetic model. The nonlinear model equations are solved using a Galerkin finite element technique, with a Newton Raphson iteration procedure being used to solve the resulting matrix equations. Model sensitivity studies are undertaken to determine the extent to which COD reduction might vary in the field with respect to time and space. The results indicate that substantial removal of leachate organics can be expected within short distances of the landfill even under the conditions of widely varying biological parameters. Model results are compared to the leachate organic reduction occurring below the Canadian Forces Base Borden sanitary landfill.