L ITERATURE R EVIEW
2.4 Numerical models
2.4.2 AMD and numerical models
Literature Review
the 2D model approach is by averaging over the vertical dimension of the aquifer and this leads to the discrepancies. And they suggested that the use of 3D models in combination with chemical heterogeneous parameters may give better results.
Molson et al. (2005) studied the pyrite oxidation process and subsequent AMD transport in the unsaturated mine waste piles by applying HYDRUS model for flow and the POLYMIN model for transport. The models were also applied to study the proccesses to stop AMD generation by arresting the infiltration of oxygen and moisture in to the unsaturated piles.
Ardejani et al. (2007) has analyzed the generation of AMD and pyrite oxidation in the backfill of opencast mines, which is exposed to atmosphere, with numerical model. This three dimensional finite volume numerical model was developed by modifying the CFD package PHOENICS.
Abdelghani et al. (2009) has studied transport nature of the mine waste contaminants within the fractured rock. This unsaturated modeling study was performed with a three dimensional flow and transport model HYDROGEOSPHERE.
Molson et al. (2012) developed a numerical model (POLYMIN/DFN) to investigate the transport behavior of AMD in discretely fractured porous media. Model was developed from the existing POLYMIN model by adding an extra feature to deal with discretely fractured network (DFN).
This model uses a two-step sequential coupling method to solve reactive transport.
Noosai et al. (2014) applied the geochemical model, PHREEQC, to investigate the treatment system for AMD. PHREEQC is designed to perform geochemical calculations, speciation and saturation-index, batch reaction and one dimensional transport process.
Literature Review
2002), effect of reactive barrier on mine water transport in aquifer (Ludwig et al. 2002) and column barrier study to reduce the acid production (Amos et al. 2004). Very few studies were attempted to simulate mobile/immobile water effects on the transport of mine drainage contaminants (Bibby, 1981 and Selim et al. 1987). Based on a review of the literature, this study attempts to analyse the immobile water effects on the transport of AMD contaminants from waste rock heap/mine tailings site to the underneath aquifer. The modified numerical model considers various physical processes (variably saturated flow, medium heterogeneity, physical non-equilibrium of the medium) and sorption reactions to simulate the AMD transport through the subsurface soil. The scope of the non-equilibrium transport study is to make the model prediction more accurate and to give insight to the process of treatment of mine water.
In addition, the model may be useful in the designing of reactive barriers.
Table 2.2 Public domain reactive transport models available in USGS site
Models General capabilities
2DFATMIC
1D/2D variably saturated flow, transport of microbes and chemicals with simple chemical reactions (decay kinetics, linear/non-linear adsorption).
3DFATMIC 1D/2D/3D variably saturated flow, transport of microbes and chemicals with simple chemical reactions (decay kinetics, linear/non-linear adsorption).
CHEMFLO 1D variably saturated flow and solute transport.
CHAIN_2D 2D water flow, heat and multi-solute transport in variably saturated porous media.
FEHM 1D/2D/3D multiphase, multicomponent, non-isothermal, reactive flow through variably saturated porous medium and fractured media
HydroBioGeoChem123 1D/2D/3D solute transport, heat transport, mixed, heterogeneous, chemical kinetics and equilibrium and coupled reactive transport in variably saturated porous media.
PESTAN 1D analytical simulation of organic solute transport in the unsaturated zone
RITZ 1D analytical simulation of unsaturated zone flow and transport of oily wastes.
SUTRA Variably saturated, variable-density ground-water flow with solute and energy transport.
UNSATCHEM 1D simulation of variably saturated water flow, heat transport, CO2 production and transport, multicomponent transport with major ion equilibrium
Literature Review
and kinetic chemistry.
UNSATCHEM-2D 2D simulation of variably saturated water flow, heat transport, CO2 production and transport, multicomponent transport with major ion equilibrium and kinetic chemistry.
VLEACH 1D simulation of advection, sorption, diffusion, and three-phase equilibration in vadose zone.
HYDRUS1D 1D simulation of water flow, heat and multiple solutes transport in variably saturated media with non- equilibrium mass transfer.
PHREEQC Chemical reaction and 1D reactive transport
VS2DI 1D/2D heat or solute transport in variably saturated porous media
HP1 1D simulation of flow water, heat and multiple solutes reactive transport in variably saturated media.
SWMS_2D 1D/2D water flow and solute transport in vadose zone.
SWMS_3D 1D/2D/3D water flow and solute transport in variably saturated porous media.
RETRASO 1D/2D multiphase flow, heat and reactive transport in variably saturated porous media.
SHAW 1D simulation of water flow, heat and solute transport in variably saturated media.
Table 2.3 Commercial reactive transport models
Models General capabilities
3DFEMFAT 3D flow and solute transport in variably saturated porous media including salt water intrusions.
AIRFLOW-SVE Simulation of vapor flow and multi-component vapor transport in unsaturated, heterogeneous and anisotropic soil.
CTRAN/W 1D/2D water flow and solute transport in variably saturated porous media.
FEFLOW 2D/3D simulation of water flow, heat and solute transport in variably saturated media.
FRAC3DVS 1D/2D/3D simulation of water flow and solute transport in variably saturated porous fractured media.
HYDROGEOCHEM 1D coupled simulation of water flow, chemical reactions and reactive solute transport in variably saturated porous media zone.
HYDROGEOCHEM2 2D coupled simulation of water flow, chemical reactions and reactive solute transport in variably saturated porous media zone.
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HYDRUS2D/3D 2D/3D simulation of flow water, heat and multiple solutes in variably saturated media.
KYSPILL 1D/2D/3D simulation of water flow and solute transport in variably saturated porous media.
MIGRATE 1D/2D water flow and solute transport in variably saturated porous media.
MODFLOW- SURFACT
1D/2D/3D MODFLOW based simulation of water flow and solute transport in variably saturated porous media.
MOFAT 1D/2D multiphase flow and transport of up to five non- inert chemical species.
POLLUTE 1D simulation of water flow and solute transport in variably saturated porous media zone.
TOUGHREACT 1D /2D/3D simulation of chemical reaction and multiphase fluids, heat and reactive transport in variably saturated porous and fractured media.