Numerical modelling of multiphase flow and transport processes in landfills

Abstract

Waste material in municipal landfills can be described as heterogeneous porous media, where flow and transport processes of gases and liquids are combined with local material degradation. This paper deals with the basic formulation of a multiphase flow and transport model applicable to the numerical analysis of coupled transport and reaction processes inside landfills. The transport model treats landfills within the framework of continuum mechanics, where flow and transport processes are described on a macroscopic level. The composition of organic and inorganic matter in the solid phase and its degradation are modelled on a microscopic scale. The degradation model captures the different reaction schemes of various microbial activities. Subsequently, transport and reaction processes have to be coupled, since emissions at the surface and from the drainage layer depend on the flow of leachate and gas, the transport of various substances and heat, and the biodegradation of organic matter. The theoretical considerations presented here are fundamental to the development of numerical models for the simulation of multiphase flow and transport processes inside landfills coupled with biochemical reactions and heat generation. The implicit modelling of leachate and gas flows including growth and decay of micro-organisms are innovative contributions to landfill modelling

A process-based inventory model for landfill CH4emissions inclusive of seasonal soil microclimate and CH4oxidation

“…Thus, CALMIM estimates annual CH 4 emissions while accounting for climate‐induced variability on transport and microbial oxidation. Although more complex models exist for predicting the flow of landfill gas as a function of diffusion and advection [ Findikakis and Leckie , 1979; Findikakis et al , 1988; Lang et al , 1989; Kindlein and Ahrens , 2006; Donovan et al , 2010; Yu et al , 2010], a number of the assumptions in these models are often violated in field settings (e.g., homogeneity of waste mass; uniform characteristics; static CH 4 generation rates). (Please consult the for a detailed discussion of diffusive versus advective processes in landfill cover soils.)…”

Estimation of Solid Waste Biomethanization: Development of Novel Methodology and Anfis Models

“…Mathematics provides a powerful logic system: there is a broad range of mathematical models developed with the aim of qualitatively and quantitatively simulating the biogas generated during the biodegradation of MSW (Ojolo et al, 2008;Kindlein, Dinkler, and Ahrens, 2006;Vavilin et al, 2006). Similarly, the use of statistics has been profuse because of its multiple applications and also because the obtained results provide straightforward interpretations (Daels et al, 2010;Akkaya and Demir, 2009;Zacharof and Butler, 2004;Gurijala, Sa, and Robinson, 1997).…”

Mathematical modeling and numerical simulation of a bioreactor landfill using Feel++

“…On the one hand, [20,21,25] present mathematical approaches to the problem but the authors deal with a single aspect of the phenomenon under analysis focusing either on microbiota activity and leachates recirculation or on gas dynamic. On the other hand, this topic has been of great interest in the engineering community [3,16,17] and several studies using both numerical and experimental approaches are available in the literature. We refer the interested reader to the review paper [1] on this subject.…”