Simulation of microbial remediation for pore-scale uranium contamination in sandstone uranium mines
In-situ microbial immobilization is often used to remediate uranium contamination in ground-water resulting from in-situ leaching sandstone uranium mines.While there is considerable experimental research on microbial remediation of uranium contamination,there is a lack of numerical simulation studies at the pore scale.For the simulation of microbial in-situ fixation of uranium contamination in sandstone uranium mines,a two-dimensional conceptual model of porous media at the pore scale was first established.Then,a liquid injection pore was used to introduce functional microbes and carbon sources into the porous media,where microbes grow and reproduced under carbon source stimulation.During their growth metabolism,they reduced U(Ⅵ)in the solution to U(Ⅳ)and immobilize it.Sim-ultaneously,the oxidative substances preferred to dissolved O2 and NO3-in groundwater that possess ox-idation capabilities on U(Ⅳ)are considered for their re-oxidation effect.Additionally,a mathematical model of the above processes is established,and the model coupling simulation is achieved using the Lattice Boltzmann Method(LBM).Finally,the simulation process takes into account the influence of factors such as porous media permeability,tortuosity,injection velocity,and microbial concentration on the migration range of uranium contamination and remediation effectiveness.The results indicated that the established model simulated the microbial remediation of uranium contamination at the pore scale in sandstone uranium mines,as well as the processes of re-oxidation and release.Moreover,the increase of permeability,injection velocity,and microbial concentration expedited uranium contamination remedia-tion.However,dissolved O2 and NO3-in groundwater affected the long-term effectiveness of the reme-diation.This study provided a reference point for the development of microbial remediation theory and numerical simulation methods for uranium contamination during the decommissioning of in-situ leaching uranium operations.Additionally,it presented a novel approach for assessing and predicting the effec-tiveness of microbial remediation techniques for groundwater uranium contamination.
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