Modeling the Influence of Biodegradation on Sanitary Landfill Settlements

Abstract. This paper presents a mathematical model to reproduce long term or secondary settlement of sanitary landfills. Sec-ondary compression is assumed to be commanded by two main processes: mechanical creep compression and the biodegradationof waste. The model introduces a biodegradation parameter that relates mass loss with volumetric variations. The biodegradationof Municipal Solid Waste (MSW) organic matter was represented through gas generation, modeled as a first order decay process.The gas generation was transformed into mass loss and used to evaluate biodegradation settlements through a mass balance equa-tion. Some qualitative approaches concerning the time origin of secondary compression processes were addressed and used in thesimulations. Strategies for obtaining model parameters are also presented and the main implications of biodegradation on settle-ment are discussed. The results predicted by the model are compared with laboratory and sanitary landfill data and reveal highlevels of agreement between measured and calculated values.