A coupled model for prediction of settlement and gas flow in MSW landfills (original) (raw)
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Landfill Settlement with Decomposition and Gas Generation
Journal of Environmental Engineering, 2005
A one-dimensional multiphase numerical model is developed to simulate the vertical settlement involving liquid and gas flows in a deformable ͑settling͒ municipal solid waste ͑MSW͒ landfill. MSW is represented by a chemical composition, and a global stoichiometric reaction is used to estimate the maximum yield of gas generation. Following the general assumption accepted in the literature, the gas generated by waste decomposition is assumed to comprise of methane ͑CH 4 ͒ and carbon dioxide ͑CO 2 ͒. The gas generation rate follows an exponentially decaying function of time. The gas generation model developed based on a first-order kinetic single-bioreactor approach includes the governing equations of gas migration, liquid flow, and landfill deformation. The Galerkin finite element method is used to solve the resulting equations. The model developed can be used to estimate the transient and ultimate settlements due to waste decomposition and gas generation in MSW landfills. The proposed model can estimate the waste porosity, gas pressure, liquid pressure, gas saturation, liquid saturation, and stress distributions in settling landfills. The results obtained for a deformable landfill are compared with a landfill having a rigid solid skeleton. Due to settlement, the depth of waste is 27% smaller in deformable landfills than that of the rigid ones.
Chemical Engineering Science - CHEM ENG SCI, 2007
In Parts I and II of this series a D model was developed for transport and reaction of gaseous mixtures in landfills, and was utilized, through computer simulations, to investigate the effect of various factors on the gases’ concentrations and the landfill's total pressure, under quasi-steady state and dynamic conditions. A fundamental problem with modelling of landfills is the severe shortage of publicly available experimental data for their static and dynamical properties, which hinders the development of accurate models for them. In the present paper we address this problem by formulating it as one of optimization, whereby the optimal spatial distributions of the porosity, permeability, tortuosity factor, and the total potential of various types of wastes for producing the gases in a landfill are determined, given some limited experimental data for a property of the landfill, such as the amount of methane which is extracted from it over a period of time. The numerical simula...
Numerical Simulation of the Radius of Influence for Landfill Gas Wells
Vadose Zone Journal, 2004
The physical properties of waste (e.g., density, porosity, saturation, permeability) largely influence gas migration In North America, most domestic waste produced is disposed in rates. Several studies treat physical properties of waste landfills. These sites generate leachate and gas, mainly CH 4 and CO 2 , which are harmful for the environment if not properly controlled.
Environmental Technology Modeling gas generation for Landfill
A methodology was developed to predict the optimum long-term spatial and temporal generation of landfill gases such as methane, carbon dioxide, ammonia, and hydrogen sulphide on post closure landfill. The model incorporated the chemical and the biochemical processes responsible for the degradation of the municipal solid waste. The developed model also takes into account the effects of heterogeneity with different layers as observed at the site of landfills morphology.
The municipal solid waste (msw) is a source of landfill gas (msw)-with methane gas content. Preoccupations for landfill gas (msw) management date back since 1976 when, at a landfill (msw) in California (USA), it turned out practically that the landfill gas (msw) with methane gas content contains a gas with high caloric value that can be collected and used for economic purposes. The landfill gas (msw) contains methane gas (30% -60% volume), carbon dioxide (45% -50% volume), hydrogen sulfide and other gases. Methane gas, carbon dioxide, nitrous oxide and other gases are listed in Kyoto Protocol as high greenhouse gases. Their ecological-rational management is both a national and global preoccupation. In terms of greenhouse gases, especially methane gas, the landfill (msw) is held responsible for 3.5% -5% of the total global greenhouse gases. Practically, the quantitative estimation of the methane gas in a municipal solid waste landfill can be done by measuring the landfill gas (msw) flow in an extraction-collection well. In Romania, a quantitative estimation relationship of methane gas from deposits (msw) was made, approaching the problem in a different way. This paper presents the calculation formula, the working algorithm, the municipal waste landfill equation and the NOMOGRAMA of a municipal solid waste landfill (msw). The NOMOGRAMA allows us to define the values for parameter -m-(number of months needed for an amount of municipal solid waste (msw) to degrade, starting with the year from which the landfill gas (msw) emission with methane gas content is calculated). Taking into account the environmental conditions for each location of municipal solid waste landfill, the calculation uses various indexes and approximations, while the fundamental parameter remains -m-defined by the NOMOGRAMA of the municipal solid waste landfill (msw). A municipal solid waste landfill (msw) is a conglomerate of waste Journal of Geoscience and Environment Protection with various biodegradation periods between 2 -3 years and 5 -10 -30 years. Degradation of waste (msw) in to dissolved organic carbon will take place in a number of months defined -m-starting with the year from which the methane gas emission with the NOMOGRAMA of the municipal solid waste landfill (msw) is calculated. The -m-values for the year of the quantitative emission of methane gas can be also done analytically, which requires good experience in the ecologic-rational management of the municipal solid waste (msw).
Parametric study of MSW landfill settlement model
Waste Management, 2011
A newly developed and validated constitutive model that accounts for primary compression and timedependent mechanical creep and biodegradation is used for parametric study to investigate the effects of model parameters on the predicted settlement of municipal solid waste (MSW) with time. The model enables the prediction of stress strain response and yield surfaces for three components of settlement: primary compression, mechanical creep, and biodegradation. The MSW parameters investigated include compression index, coefficient of earth pressure at-rest, overconsolidation ratio, and biodegradation parameters of MSW. A comparison of the predicted settlements for typical MSW landfill conditions showed significant differences in time-settlement response depending on the selected model input parameters. The effect of lift thickness of MSW on predicted settlement is also investigated. Overall, the study shows that the variation in the model parameters can lead to significantly different results; therefore, the model parameter values should be carefully selected to predict landfill settlements accurately. It is shown that the proposed model captures the time settlement response which is in general agreement with the results obtained from the other two reported models having similar features.
Numerical modelling of lateral landfill gas migration
Journal of Solid Waste Technology and Management
Dé pa rtem e", .t"t3::l "TH:iî3n ie seo r o g i q ue Quebec (OC) G1K7p4, Canadâ ABSTRACT The decomposition of the.organic content of disposed waste results in production of heat and landfill gas, composed mainly of methane and cabon dioxide. The develJped pressure, concentration and.temperature grad.ients lead to gas emissions to the atmàspÀ"i! "nc to tateral migration through.sunounding soils. Environmeital and safety issues "="o.iàt"o wth landfill gas require control of the off-site gas migration. The numerical model TOUGH2-LGM was used to smulate the landfill gas migration through unsalurated sands adjacent-to-gr" èt-eti;";;;;.: Grès landfill site in Quebec' Ôanada, and-to assist the design or rné àtr-iltàlas controt system in compliance with regulatory requirements. The model.simulàtes me mitrarioi or rour fluio'coâpo.. nents (water, nitrogen, methane and carbon dioxide) and one en"rgf "omionent (heat) in par_ tially saturated media. Two examples are simulated: free lateral g"î rigriion, and lateral gas migration towards a horizontal eldraction well. Results show thal a uaciuur of 0.5 kpa in the horizontal well installed '10 m from the landfill at 3 m depth is sufficient to limit further lateral migration of methane. The results also show the differeni no* pàttàrns ior.'r.tn"n" and atmospheric air, and demonstrate the advantages of the multicomponent representation of the gas phase.
Depsim: numerical 3D-simulation of the water, gas and solid phase in a landfill
International Journal of Sustainable Development and Planning, 2016
The model depSIM is a dump simulation model, which allows a detailed and time-scaled focus into the complex processes of a landfill. Description of the mechanical model: The biological, chemical and physical processes in the waste body are closely connected with each other and can be described mechanically. Therefore, a number of differential equations are needed and implemented in the model. The porous media body is examined under the acceptance of a compressible gas phase, a materially incompressible solid state, an organic phase and a liquid phase. For the verification of the numerical model the long-time behaviour (100 years) was simulated. Further details about the model and the mechanical background are summarized in Robeck, Ricken et Widmann: A finite element simulation model of biological conversion processes in landfills [1]. Use potentials: The developed model allows a differentiated, time wise and locally calculation and representation of the temperature, the organic conversion rate, the local pressure ratios and the gas current speeds. There were several case studies with the depSIM model in Germany which show the correlation between the temperature, gas production and gas potential. Therefore three different landfills were evaluated. Here, in the correlation between measured temperature in the landfill body and the temperature in the model was shown. The average divergence between both was less than 2 degree. By the detailed calculation of the gas speeds in every point of the dump an essential improvement arises compared with conventional arithmetic models for gas forecast and gas capture. These forecast models are based on estimated initial parameters. This allows only forecasts for a complete dump or a dump segment, but allows no coupled calculation of the relevant parameters. The model depSIM offers a spatially differentiated consideration of the gas production. However, just a spatially exact, quantitative forecast of the gas production is necessary for dump operator and authorities. The right forecast is elementary for the right dimensioning of the gas collection system and gas treatment and the possible use in combined heat and power units. All gas streams can be shown with the simulation model along the dump surface spatially and time wise differentiated. This allows a locally differentiated dump gas management with a division in areas with active or passive gas collection or to estimate the feasibility of a methane oxidation layer.
Environmental Modeling & Assessment, 2010
A model to simulate gas, heat, and moisture transport through a sanitary landfill has been developed. The model not only considers the different processes that go on in a landfill but also the oxidation of methane in the final cover. The model was calibrated using published results and field data from a pilot scale landfill in Calgary. The model captures the physics of the different processes quite well. Simulations from the model show that waste permeability had a significant impact on the temperature, pressure distribution, and flux from a landfill. The presence of the final and intermediate covers enhanced the gas storage capacity of the landfill. Biodegradation of the waste was enhanced as the final cover minimized the atmospheric influences. In addition, the composition of landfill gas emitted to the atmosphere was significantly different from the composition of gas generated in landfill due to the presence of covers as some of the methane is oxidized to carbon dioxide. There was no significant benefit of using a final cover of higher depth. The presence and number of intermediate covers had an impact on gas flux and temperature distribution within a landfill.