3D Field-Scale Reactive Transport Modeling of In ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

3D Field-Scale Reactive Transport Modeling of In Situ Immobilization of Uranium in Structured Porous Media via Biostimulation
Author:Yilin Fang <yilin.fang@pnl.gov> (Pacific Northwest National Laboratory)
Timothy Scheibe <tim.scheibe@pnl.gov> (Pacific Northwest National Laboratory)
Eric Roden <eroden@geology.wisc.edu> (University of Wisconsin)
Wiwat Kamolpornwijit <wiwat.kamolpornwijit@pnl.gov> (Pacific Northwest National Laboratory)
Scott Brooks <brookssc@ornl.gov> (Oak Ridge National Laboratory)
Presenter:Yilin Fang <yilin.fang@pnl.gov> (Pacific Northwest National Laboratory)
Date: 2006-06-18     Track: Special Sessions     Session: Multi-Disciplinary Approaches To Reactive Transport Simulation In Aquifer Systems

A two-month-long ethanol injection experiment was conducted to study the impacts of porous media structure (i.e., heterogeneity existing at multiple scales) on the effectiveness of metal/radionuclide bioremediation in a highly heterogeneous unconfined aquifer near Oak Ridge, TN, USA. We have constructed a 3D field-scale groundwater flow and multicomponent reactive transport model to simulate the experimental observations. The model incorporates a suite of abiotic reactions and microbially-mediated redox reactions for multiple terminal electron accepting processes (TEAPs) including soluble oxygen, nitrate, U(VI) and sulfate and solid- phase electron acceptors. Different biomass populations are considered in the model. Growth of these populations is derived from the bioenergetics-based approach in which the partitioning of electron flow between energy generation and cell biomass production is dependent on the free energy of the corresponding TEAP. TEAP reaction rates were free energy constrained. The TEAP model and reaction system have been formulated and used to simulate laboratory batch experimental observations. We conducted the field-scale simulation starting with the reaction system and parameters obtained from the batch experiment and hydrologic parameters estimated from the results of pumping tests and water level monitoring and model interpretation of a tracer test conducted at the field in August 2004. Reaction parameters were investigated to compare simulation results and field experiment observations.