Natural attenuation and bioremediation model, modeling, modelling software
RT3D
RT3D is a multi-species reactive transport model developed by the Battelle Pacific Northwest National Laboratory. RT3D is well-suited for simulating natural attenuation and bioremediation. RT3D is a modified version of MT3DMS that utilizes alternate Chemical Reaction packages. Numerous pre-defined reactions are available including instantaneous aerobic degradation, BTEX degradation with multiple electron acceptors, sequential anaerobic degradation of PCE/TCE, and combined aerobic/anaerobic degradation of PCE/TCE. For special cases, an option is provided for creating user-defined reactions. RT3D simulations can be set up quickly and easily using GMS. A wide array of options are available for pre and postprocessing RT3D models.
SEAM3D
SEAM3D is a reactive transport model used to simulate complex biodegradation problems involving multiple substrates and multiple electron acceptors. SEAM3D was developed by Mark Widdowson at Virginia Tech University.
SEAM3D is based on the MT3DMS code. In addition to the regular MT3DMS modules, SEAM3D includes a Biodegradation package and an NAPL Dissolution package. The Biodegradation package is used to simulate complex degradation reactions involving hydrocarbon substrates. Multiple electron acceptors, nutrients, daughter products, and microcolonies can be simulated. The NAPL Dissolution package is used to accurately simulate a floating NAPL plume acting as a contaminant source. A SEAM3D simulation can have as many as 27 species. GMS is especially well-suited for managing such large and complex data sets.
FEMWATER
FEMWATER is a three-dimensional finite element groundwater model. It can be used to simulate flow and transport in both the saturated and the unsaturated zone. Furthermore, the flow and transport can be coupled to simulate density dependent problems such as salinity intrusion.
One of the advantages of the finite element method used by FEMWATER is that model boundaries and stratigraphic units can be modeled precisely. Furthermore, since FEMWATER simulates flow in the unsaturated zone, the entire aquifer is modeled and sources and sinks can be directly represented in the mesh and boundary conditions, unlike the conductance approach that must be used with external sources/sinks in MODFLOW. The disadvantage of FEMWATER is that it is memory intensive, solutions can be time-consuming, and convergence is more difficult.
GMS can be used to construct complex FEMWATER models. The conceptual model approach can be used to simplify mesh generation and parameter/boundary condition assignment. A suite of powerful 3D visualization tools are available for postprocessing FEMWATER models including animations, cross sections, and iso-surface plots.
SEEP2D
SEEP2D is a 2D finite element, steady state, flow model. It is typically used for profile models, i.e., cross-section models representing a vertical slice through a flow system which is symmetric in the third dimension. Examples include earth dams, levees, sheet piles, etc. The output from SEEP2D can be used to plot complete flow nets.
SEEP2D can be used to simulate both confined and unconfined flow problems. For unconfined problems the model can be limited to the saturated zone or the flow can be simulated in both the saturated and unsaturated zones.
UTCHEM
UTCHEM is a multiphase flow and transport model developed by the Center for Petroleum and Geosystems Engineering at the University of Texas at Austin. UTCHEM is ideally suited for pump and treat simulations, particularly the simulation of surfactant-enhanced aquifer remediation (SEAR) and DNAPL transport. UTCHEM is a mature model that has been widely used. The UTCHEM solver is efficient and robust. Future iterations of the GMS/UTCHEM interface will include the simulation of biodegradation.
Units
When building a model in GMS, a global set of units can be entered for the model. These units are then used to post a units reminder next to each data entry field throughout the model interface to help ensure consistency of units.
Regional to Local
For many modeling studies, determining an appropriate set of boundary conditions can be difficult. In such cases, it is often convenient to perform the modeling study in two phases. In the first phase, a large, regional scale model is constructed and the model is extended to well-defined boundaries. During the second stage, a second, smaller, local scale model is constructed that occupies a small area within the regional model. Head and layer data are interpolated from the regional to the local model. A more detailed representation of the local flow conditions, including low capacity wells and barriers not included in the regional flow model can be constructed in the local scale model. Regional to local model conversion is often referred to as "telescopic grid refinement." GMS provides a convenient set of tools that can be used for regional to local model conversion.
Geostatistics
GMS supports a powerful array of options for geostatistics and interpolation in the 2D and 3D Scatter Point modules.
The following interpolation options are supported:
- Linear
- IDW
- Constant, gradient-plane, and quadratic nodal functions
- Multiple search/subset schemes
- Clough-Tocher
- Natural Neighbor
- Constant, gradient-plane, and quadratic nodal functions
- Kriging
- Ordinary, Universal, Zonal, and Indicator
- Indicator simulations
- Directional variograms
2D Geostatistics
2D geostatistics are used for a variety of tasks including generating contour plots of 2D functions from scatter point measurements, interpolating elevations for MODFLOW layer arrays, and performing regional to local model conversion.
3D Geostatistics
3D geostatistics are used for 3D plume characterization and for generating initial conditions for 3D models.
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