|Faculty of Engineering and the Environment|
|Current Research||Landfill Degradation and Transport Model (LDAT)|
The LDAT numerical model of landfill degradation and transport processes was originally developed to support laboratory and field tests being carried out by the University of Southampton (UK) Waste Management Research Group and others, (Parker, Powrie et al. 1999; White, Robinson et al. 2001; White and Robinson 2002; White, Robinson et al. 2003; White, Robinson et al. 2004e).
|Energy and resource recovery from waste|
Characteristics of the LDAT numerical model
The LDAT model is structured on the basis of a two dimensional finite difference grid of constant volume elements containing solid waste, leachate and gas. Leachate and gas flows through the solid matrix are modelled in a conventional way but are coupled to the degradation and settlement of the solids (White 2004c; White 2006; White and Beaven 2008; Zardava, Powrie et al. 2009e; Zardava, Powrie et al. 2009f).
The grid geometry can be varied and different element properties chosen for each element. In addition all element properties, including temperature functions, have default values available. Any system of units may be used. The model caters for a variety of waste types which are specified as percentages of the total waste in an element. Each waste can be assigned its own bioavailability and catalytic factor to control its degradation rate. The waste types each have independent chemical degradation pathways. (White 2004c). The effects of gas solubility and changes in the water phase from liquid to vapour are modelled. Dry density and permeability are related to effective stress after (Powrie and Beaven 1999). A ratio of vertical to horizontal permeability, and atmospheric pressure, may also be applied. Functions relating leachate saturation to capillary pressure, effective gas density, effective liquid density, gas permeability, liquid permeability and dry density have been introduced into the LDAT model code, and the consequential changes to the flow algorithms and boundary conditions have been made. Heat transfer is modelled using the parameters specific heat and thermal conductivity, with heat generation based on gas production. Temperature dependence of the following parameters is included; gas and liquid viscosities, bacteria growth rates, death rates and half saturation constants, pH and pH inhibition factor calculation parameters.
|School of Civil Engineering and the Environment||
The output from LDAT gives the time history for all of the properties of each element in the model. These properties include; solids, water, acid and gas contents, vented gas, bacteria populations, and settlement. The latest version of the code can be downloaded here:
LDAT code and documentation pack -This zip folder contains the Sep 2009 v5 LDAT code, the compiled CVE.exe installer, and documentation. It is intended for downloading by interested researchers. Both the code and the documentation are the product of ongoing academic research. The material is made available for the purposes of collaborative research only. The authors and the University of Southampton accept no liability for the consequences of inappropriate use of the material, in particular use of the material for commercial purposes.
· EPSRC grant GR/M87023: A parametric sensitivity analysis of landfill processes
· Legacy Fund of the Landfill Tax Credit Scheme: Modelling leachate and gas control horizontal wells
· Onyx Environmental Trust:Science and strategies for the sustainable management of residual wastes and landfills
· Defra: Forced air flow and distribution in landfilled waste
· EPSRC grant EP/E041965/1: Science and strategies for the long term management of and remediation of landfills
The model has been configured to support investigations related to the compression and consolidation characteristics of biodegrading solid waste, and the acceleration and stabilisation of solid waste degradation using leachate recirculation, aerobic treatment and flushing (Hudson, Beaven et al. 2004; Rees-White, Beaven et al. 2008; Nayagum, White et al. 2009a; Nayagum, White et al. 2009b).
LDAT has also been used to review the self consistency of the Rainham landfill horizontal well dataset, (Cox 2002; Powrie, Cox et al. 2003; Beaven, White et al. 2004; White 2004b; Beaven, White et al. 2005).
An EPSRC funded study of the compression and consolidation of degrading household waste has produced data that has been used to calibrate the LDAT model. (White 2004a; White, Haarstrick et al. 2005; White 2007b; White and Beaven 2008; White 2008h). The underlying degradation algorithms in LDAT have also been applied to assess the effect of moisture content on degradation rates in waste, (Burton, Beaven et al. 2004).
LDAT has been applied to the case of gravity driven vertical drainage, taking into account capillary forces on the movement of moisture and gas in waste - both theoretically and using experimental data (Nayagum, White et al. 2009b; Zardava, Powrie et al. 2009e). Field data from the Defra funded Aerox project involving the aeration of municipal waste at the Pitsea landfill facility, have provided a further check on the model’s representation of gas flow, waste degradation and heat transport (Beaven, White et al. 2008; Rees-White, Beaven et al. 2008; Nayagum, White et al. 2009a).
Compiled versions of LDAT and documentation have been supplied to Julia Lamborn, Melbourne, Emoke Imre , Budapest, Jim Hanson, CalPoly, USA, and Hideki Yoshida, Hokkaido, Japan.
Beaven, R., J. K. White, et al. (2008). " Application of the University of Southampton landfill degradation and transport model (LDAT) to an aerobic treatment field experiment." Proceedings of the Global Waste Management Symposium 2008 Copper Mountain conference centre Colorado USA.
Beaven, R. P., J. K. White, et al. (2004). "Research into the effect of high suction pressures on a horizontal leachate well." Proceedings of the Waste 2004 Conference, Stratford-upon-Avon, Warwickshire, UK September 2004.
Beaven, R. P., J. K. White, et al. (2005). "Modelling the performance of a horizontal leachate drain." Proc. Sardinia 2005, Tenth International Waste Management and Landfill Symposium, Cagliari, Italy, October 2005.
Burton, S. A. Q., R. P. Beaven, et al. (2004). "The effect of moisture content in controlling landfill gas production and its application to a model for landfill refuse decomposition." Proceedings of the Waste 2004 Conference, Stratford-upon-Avon, Warwickshire, UK September 2004.
Cox, S. (2002). "The use of horizontal wells for leachate and gas control in landfills." University of Southampton PhD thesis December 2002.
Hudson, A., R. P. Beaven, et al. (2004). "Modelling the compression behaviour of landfilled domestic waste." Waste Management and Research Vol 24, 3 March 2004.
Nayagum, D., J. K. White, et al. (2009a). " Modelling study of field-scale aerobic treatment of waste using forced-air injection." Twelfth International Waste Management and Landfill Symposium 5-9 October 2009 Sardinia Italy.
Nayagum, D., J. K. White, et al. (2009b). " Numerical modelling of the flow dynamics of air and leachate through waste material under vertical drainage and forced-air flow." 3rd International Workshop in Hydro-Physico-Mechanics of Landfills Braunscheig Germany.
Nayagum D., J.K. White, K. Zardava and D. Holmes. Investigating dynamic effects of capillary pressure-saturation relationships on unsaturated flow in waste materials. Fourth International Workshop “Hydro-Physico-Mechanics of Landfills”, Santander, Spain, 27-28 April, 2011
Parker, L. J., W. Powrie, et al. (1999). "The measurement of the geotechnical and hydrogeological properties of degrading solid waste." Sardinia ‘99, Seventh International Waste Management and Landfill Symposium, S. Margherita di Pula, Cagliari, Italy, October 1999.
Powrie, W. and R. P. Beaven (1999). "Hydraulic properties of household waste and implications for landfills." Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, 1999, 137, Oct., pp 235-247.
Powrie, W., S. Cox, et al. (2003). "Horizontal wells for leachate control in landfills." Sardinia 2003, Ninth International Waste Management and Landfill Symposium, S. Margherita di Pula, Cagliari, Italy, October 2003.
Rees-White, T., R. Beaven, et al. (2008). " Monitoring and modeling air flow and distribution at a forced-air aerobic waste treatment plant." Waste 2008 Stratford-upon-Avon 16-17 September 2008 pp 59-68.
J.K. White and D. Nayagum. Landfill modelling challenge – Application of the University of Southampton landfill process model LDAT. Fourth International Workshop “Hydro-Physico-Mechanics of Landfills”, Santander, Spain, 27-28 April, 2011.
White, J. K. (2004a). "A study of Consolidating Anaerobic Reactor (CAR) test results in the context of the Southampton Landfill Degradation and transport model (LDAT)." Legacy Fund Project Report 2, October 2004.
White, J. K. (2004b). "Preliminary report on gas and leachate transport modelling." Legacy Fund Project Report 5, April 2004.
White, J. K. (2004c). "Preliminary report on solid waste chemistry modelling." Legacy Fund Project Report 6.
White, J. K. (2006). "A review of the theory relating to the evolution and movement of gas in waste materials and proposals for the design of laboratory experiments to investigate this theory." Science and strategies for the management and remediation of landfills. Sub-package funded by Onyx. Final report. December 2006.
White, J. K. (2007b). "The application of the University of Southampton Landfill Degradation and Transport model LDAT to the HPM2 Challenge dataset derived from two Consolidating Anaerobic Reactors by Ivanova et al (2007)." 2nd Workshop on the Hydro-Physico-Mechanical-Properties of Wastes (HPM2), Southampton UK, 17th-19th April 2007.
White, J. K. (2008h). " The application of LDAT to the HPM2 Challenge." Proceedings of the Institution of Civil Engineers Waste and Resource Management 161 November 2008 Issue WR4 pp. 137 - 146.
White, J. K. and R. P. Beaven (2008). "Modelling the liquid phase in the University of Southampton model LDAT." Proceedings 1st Middle European Conference on Landfill Technology February 6 -8 2008 Budapest Hungary.
White, J. K., A. Haarstrick, et al. (2005). "Experimental investigations of organic waste degradation and comparison of two numerical simulations." Proc. Sardinia 2005, Tenth International Waste Management and Landfill Symposium, Cagliari, Italy, October 2005.
White, J. K. and J. P. Robinson (2002). "The combined use of simple and complex models for the management and control of experimental and real landfill processes." Proceedings of the Waste 2002 Conference, Stratford-upon-Avon, Warwickshire, UK September 2002.
White, J. K., J. P. Robinson, et al. (2001). "A framework to contain a spatially distributed model of the degradation of solid waste in landfills." Sardinia 2001, Eighth International Waste Management and Landfill Symposium, S. Margherita di Pula, Cagliari, Italy, October 2001.
White, J. K., J. P. Robinson, et al. (2003). "A framework to contain a spatially distributed model of the degradation of solid waste in landfills." Journal of Waste Management and Research, vol. 21, part 4, September 2003.
White, J. K., J. P. Robinson, et al. (2004e). "Modelling the biochemical degradation of solid waste in landfills." Waste Management, Vol 23,3 March 2004.
Zardava, K., W. Powrie, et al. (2009e). "The determination of the moisture retention characteristics of waste materials using vertical drainage experiments." 3rd International Workshop in Hydro-Physico-Mechanics of Landfills Braunschweig Germany.
Zardava, K., W. Powrie, et al. (2009f). "The determination of the retention characteristics of waste materials using vertical drainage experiments." Twelfth International waste Management and Landfill Symposium 5-9 October 2009 Sardinia Italy.