LDAT workshop Jim White

Overview Introduction to LDAT Sources of information www.ldatmodel.com Working with LDAT Summary

Overview Introduction to LDAT Sources of information www.ldatmodel.com Working with LDAT Summary LDAT solves the landfill process constitutive equations using a finite difference algorithm within a framework of rectangular elementary volumes

Side boundary elements not shown LDAT solves the landfill process constitutive equations using a finite difference algorithm within a framework of rectangular elementary volumes Active elements Boundary elements Side boundary elements not shown The element grid format has the potential to model in one dimension as a simple stack or in three dimensions for more complex cases. Boundary conditions are applied through designated boundary elements.

Single element 5 element stack 35 element 2D 140 element 3D

Side boundary elements not shown k j i [2, 0, 3] [5, 2, 1] i, j, k index system

Side boundary elements not shown z y x (1.5, 0.05, 2.5) (4.5, -1.5, 0.5) x, y, z co-ordinate system

Landfill Modelling Challenge 1 (LMC1) Key 1. Consolidation load piston 2. Gas extraction 3. Load platen 4. Lower drainage layer 5. Upper drainage layer 6. Waste sample 7. Leachate/gas interface 8. Leachate recirculation route

LMC2 example Add picture and references

LMC2 configuration Footprint assumed 80m x 55m = 5,040 m2 Forced gas extraction wells (6 no.) Impermeable cover Leachate injection layer Deep (6 no.) and shallow (2 no.) leachate monitoring wells 8.5m Leachate injection layer 3m 0.3m Leachate head limited to 1m Gravel drainage layer 300 mm deep with HDPE pipework Impermeable base Footprint assumed 80m x 55m = 5,040 m2 Volume 8m x 5,040 m2 = 40,320 m3 Dry mass 17,352T Dry density 431 kg/m3 Water content 27%

LDAT element configuration Boundary element Waste element

Transient boundary conditions Boundary element Waste element Removal from basal drain to storage Removal from basal drain to recirculation Removal from clean water store to landfill

LDAT element and sub-models Gas solubility Waste degradation Element

Overview Introduction to LDAT Sources of information www.ldatmodel.com Working with LDAT Summary LDAT solves the landfill process constitutive equations using a finite difference algorithm within a framework of rectangular elementary volumes

LDAT solves the landfill process constitutive equations using a finite difference algorithm within a framework of rectangular elementary volumes source transport density concentration rate of change of mass

LDAT constitutive equation Calculate source terms Solve for pressures Solve for concentrations Solve for settlements The computational sequence is to calculate the source terms, solve for the pressure fields and back calculate the concentrations and settlement.

LDAT calculation flow Edit input data Increment time For each element Results file Display results

LDAT element sub-models Changes due to chemical reactions Leachate chemistry 1. Chemical equilibrium calculation 2. Gas solubility model (Henry’s Law) 3. Water vapour model 4. Heat generation model Biochemical degradation Stoichiometry 5. Degradable material and products 6. Bacteria growth and products 7. Bacteria decay and products Stoichiometric rates 8. Degradable material rates 9. Bacteria growth rates (pH and moisture content inhibition) 10. Bacteria decay rates Changes due to flow and settlement Gas transport 11. Gas permeability model Liquid transport 12. Liquid permeability model Settlement 13. Dry density model Heat transfer 14. Convection-conduction model

LDAT sub-model linkage Changes due to chemical reactions Leachate chemistry 1. Chemical equilibrium calculation 2. Gas solubility model (Henry’s Law) 3. Water vapour model 4. Heat generation model Biochemical degradation Stoichiometry 5. Degradable material and products 6. Bacteria growth and products 7. Bacteria decay and products Stoichiometric rates 8. Degradable material rates 9. Bacteria growth rates (pH and moisture content inhibition) 10. Bacteria decay rates Changes due to flow and settlement Gas transport 11. Gas permeability model Liquid transport 12. Liquid permeability model Settlement 13. Dry density model Heat transfer 14. Convection-conduction model Coupled using LDAT algorithm – also controls calculation and file management system Coupled using degradation matrix Coupled using capillary pressure model Coupled using dry density model

Overview Introduction to LDAT Sources of information www.ldatmodel.com Working with LDAT Summary

LDAT process Notes Gas solubility Waste degradation Element

LDAT publications First publication: White, J.K., Robinson, J.P. and Ren, Q. (2001) A framework to contain a spatially distributed model of the degradation of solid waste in landfills., S. Margherita di Pula, Cagliari, Italy.

LDAT publications

LDAT publications (latest and definitive)

Overview Introduction to LDAT Sources of information www.ldatmodel.com Working with LDAT Summary