Modeling anaerobic bioreactor landfills in methanogenic phase: long term and short term behaviors.

We have developed a mathematical model to simulate the behavior of real bioreactor landfills in the anaerobic methanogenic phase. This coupled model is composed of a two-phase flow and a biological model based on Darcy's law and Monod's model, respectively. This model considers bacterial activity and biological behavior as a function of temperature and makes it possible to study the thermo-biological behavior of bioreactor landfills with temperature changes. In this model we consider different effects of saturation on solid waste degradation. These effects consist of increasing hydrolysis with saturation and also decreasing the concentration of volatile fatty acids (VFAs) and activating the methanogenic biomass. This paper presents first the mathematical coupled model and the numerical methods used to solve the conservation equations. The numerical model is then used to simulate two bioreactor landfills. This paper presents the results of long and short (with leachate recirculation) term numerical simulations comparing them with site results. Finally results as well as advantages and drawbacks of the model are discussed. The results show that the mathematical model is able to reproduce the hydro-thermo-biological behavior of a bioreactor landfill in different conditions, with and without leachate recirculation, and leads to a better understanding of important thermal and biological parameters.