Saturated – unsaturated flow and multiphase transport modeling

1. Saturated – unsaturated flow and multiphase transport modeling by Michel E. Rahbeh Rabi H. Mohtar Tong Zhai

2. Contents • Introduction • Governing Equations • I/O for the ground water flow model • I/O for the ground water transport model • I/O for the air sparging/ soil vapor extraction – flow component • I/O for the air sparging/ soil vapor extraction – multiphase transport component. • Sample output • Transport in saturated porous media • Unsaturated flow (air sparging) • Multiphase transport • Web application

3. Introduction • The model was developed to solve specifically for contaminant removal by advective air flux induced by air injection (air sparging) or extraction (soil vapor extraction) • However the same code can be used to solver for conventional heterogeneous flow and contaminant transport problems

4. Introduction • Volatile Organic Contaminant (VOC) can removed from soil and ground water by an advective air flux. • Advective air flux can be either induced by extracting air (Soil Vapor Extraction, SVE), or injecting air (Soil sparging AS). • The SVE and AS can be operated separately or simultaneously as shown in the following figure

5. As air flowing upward the contaminant is mobilized into the advective air stream. • Also the oxygenation of the subsurface may trigger aerobic metabolism of the organic contaminants

6. GOAL To develop suitable tool to help understand mass transfer processes during air advective air flux, in order to aid in the design and operation of remediation systems that involve advective air flux such air sparging and Soil vapor Extraction (AS/SVE). • The model consists of two module • Multiphase transient module, and • unsaturated steady flow module kdeg kd : Sorption/desorption ks: Stripping kv: volitalization kdis:dissolution kdeg: biodegradation Solid Phase Ss Aqueous phase Caq Non-aqueous phase Cnaq Total Removal kd kdis kv Gaseous phase Cg ks

7. Unsaturated flow model kdeg kd : Sorption/ desorption ks: Stripping kv: volitalization kdis:dissolution kdeg: biodegradation Solid Phase Ss kdis Aqueous phase Caq Non-aqueous phase Cnaq Total Removal kd kv ks Gaseous phase Cg

8. Aqueous phase kdeg kd : Sorption/ desorption ks: Stripping kv: volitalization kdis:dissolution kdeg:biodegradation Solid Phase Ss Aqueous phase Caq Non-aqueous phase Cnaq Total Removal kd kdis kv ks Gaseous phase Cg

9. Gaseous Phase kdeg kd : Sorption/desorption ks: Stripping kv: volitalization kdis:dissolution kdeg: biodegradation Solid Phase Ss Aqueous phase Caq Non-aqueous phase Cnaq Total Removal kd kdis kv ks Gaseous phase Cg

10. Solid Phase kdeg Solid Phase Ss kd Aqueous phase Caq Non-aqueous phase Cnaq Total Removal kd : Sorption/ desorption ks: Stripping kv: volitalization kdis:dissolution kdeg: biodegradation kdis kv ks Gaseous phase Cg

11. Non Aqueous Liquid Phase kdeg Solid Phase Ss Aqueous phase Caq Non-aqueous phase Cnaq Total Removal kd : Sorption/ desorption ks: Stripping kv: volitalization kdis:dissolution kdeg: biodegradation kdis kd kv ks Gaseous phase Cg

12. Numerical Formulation

13. First order mass transfer coefficients

14. Input/output for air sparging/SVE air flow component • Input • Boundary conditions: Capillary pressure • Intrinsic permeability • Coefficients for pressure-saturation relationship. The pore size distribution index (Lamda) for Brooks-Corey relation. • Output • Capillary head distribution

15. Input/output for the Ground water flow • Input • Hydraulic conductivity or transmissivity • Boundary conditions : water table heads or piezometric pressure. • Output • water table heads or piezometric pressure distribution

16. Input / output for the ground water transport • Input • Dispersivity • Ground water velocities or, water table heads or piezometric pressure distribution. • Initial condition : concentration profile C(0,x,y) • Output • Concentration profile C(t,x,y)

17. Sol Vol KH kbio Dmg Dmaq koc  contaminant Input flow and transport model Model output caq(x,y,t) cg(x,y,t) Ss(x,y,t) Xnaq(x,y,t) caq(t=0) cg(t=0) Ss(t=0) Xnaq(t=0) Initial Conditions  foc d50 Dg Daq Porous Medium Input Input/output for air sparging/SVE Multiphase Flow Component

18. Example output ground water transport Comparison between analytical and numerical solutions of instantaneous injection of a solute unit mass in one-dimensional single phase, where Pv=1 and PD=0.05. The continuous lines represent the numerical solution, where as, the data points analytical solutions the

19. Example output ground water transport Comparison between analytical and numerical solutions of continuous solute injection in one-dimensional single phase, where Pv=1, Pe=0.05. The continuous lines represent the numerical solution, where as, the data points analytical solutions

20. Example output ground water transport The comparison between the analytical and numerical solution of an instantaneous injection of a unit mass of a contaminant in two-dimensional single phases domain, where

21. Example output Air sparging flow component

22. Example output air sparging multiphase component

23. WEB APPLICATION