Perez Lazaro J, Parashar Rishi, Plymale Andrew, Scheibe Timothy D
Desert Research Institute, Reno, NV, USA.
Desert Research Institute, Reno, NV, USA.
Water Res. 2022 Feb 1;209:117896. doi: 10.1016/j.watres.2021.117896. Epub 2021 Nov 25.
Microbial biofilms are ubiquitous within porous media and the dynamics of their growth influence surface and subsurface flow patterns which impacts the physical properties of porous media and large-scale transport of solutes. A two-dimensional pore-scale numerical model was used to evaluate the impact of biofilm-induced flow heterogeneities on conservative transport. Our study integrates experimental biofilm images of Paenibacillus 300A strain in a microfluidic device packed with cylindrical grains in a hexagonal distribution, with mathematical modeling. Biofilm is represented as a synthetic porous structure with locally varying physical properties that honors the impact of biofilm on the porous medium. We find that biofilm plays a major role in shaping the observed conservative transport dynamics by enhancing anomalous characteristics. More specifically, when biofilm is present, the pore structure in our geometry becomes more spatially correlated. We observe intermittent behavior in the Lagrangian velocities that switches between fast transport periods and long trapping events. Our results suggest that intermittency enhances solute spreading in breakthrough curves which exhibit extreme anomalous slope at intermediate times and very marked late solute arrival due to solute retention. The efficiency of solute retention by the biofilm is controlled by a transport regime which can extend the tailing in the concentration breakthrough curves. These results indicate that solute retention by the biofilm exerts a strong control on conservative solute transport at pore-scale, a role that to date has not received enough attention.
微生物生物膜在多孔介质中无处不在，其生长动态会影响地表和地下流动模式，进而影响多孔介质的物理性质以及溶质的大规模输运。我们使用二维孔隙尺度数值模型来评估生物膜诱导的流动非均质性对保守输运的影响。我们的研究将微流控装置中以六边形分布填充圆柱形颗粒的情况下，实验获得的芽孢杆菌300A菌株生物膜图像与数学建模相结合。生物膜被表示为一种具有局部变化物理性质的合成多孔结构，该结构考虑了生物膜对多孔介质的影响。我们发现，生物膜通过增强异常特性，在塑造观测到的保守输运动态方面发挥着重要作用。更具体地说，当存在生物膜时，我们模型中的孔隙结构在空间上的相关性变得更强。我们在拉格朗日速度中观察到间歇性行为，这种行为在快速输运期和长时间捕获事件之间切换。我们的结果表明，间歇性增强了突破曲线中的溶质扩散，这些曲线在中间时间呈现出极端的异常斜率，并且由于溶质滞留，溶质到达时间很晚。生物膜对溶质的保留效率受一种输运机制控制，这种机制可以延长浓度突破曲线中的拖尾现象。这些结果表明，生物膜对溶质的保留在孔隙尺度上对保守溶质输运具有很强的控制作用，而这一作用迄今为止尚未得到足够的关注。
