1. LDAT workshop
Jim White

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

3. 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

4. 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.

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

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

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

10. 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

11. LMC2 example
Add picture and references

12. 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%

13. LDAT element configuration
Boundary element
Waste element

14. 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

15. LDAT element and sub-models
Gas solubility
Waste degradation
Element

16. 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

17. 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

18. 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.

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

20. 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

21. 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

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

23. LDAT process Notes
Gas solubility
Waste degradation
Element

24. 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.

25. LDAT publications

26. LDAT publications (latest and definitive)

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