Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22904-4741, USA.
Environ Sci Technol. 2010 Jan 15;44(2):780-6. doi: 10.1021/es902496v.
A two-dimensional mathematical model was developed to simulate transport phenomena of chemotactic bacteria in a sand-packed column designed with structured physical heterogeneity in the presence of a localized chemical source. In contrast to mathematical models in previous research work, in which bacteria were typically treated as immobile colloids, this model incorporated a convective-like chemotaxis term to represent chemotactic migration. Consistency between experimental observation and model prediction supported the assertions that (1) dispersion-induced microbial transfer between adjacent conductive zones occurred at the interface and had little influence on bacterial transport in the bulk flow of the permeable layers and (2) the enhanced transverse bacterial migration in chemotactic experiments relative to nonchemotactic controls was mainly due to directed migration toward the chemical source zone. On the basis of parameter sensitivity analysis, chemotactic parameters determined in bulk aqueous fluid were adequate to predict the microbial transport in our intermediate-scale porous media system. Additionally, the analysis of adsorption coefficient values supported the observation of a previous study that microbial deposition to the surface of porous media might be decreased under the effect of chemoattractant gradients. By quantitatively describing bacterial transport and distribution in a heterogeneous system, this mathematical model serves to advance our understanding of chemotaxis and motility effects in granular media systems and provides insights for modeling microbial transport in in situ microbial processes.
建立了二维数学模型，以模拟在存在局部化学源的情况下，结构物理异质性设计的沙填充柱中趋化细菌的输运现象。与之前研究工作中的数学模型不同，在这些模型中，细菌通常被视为不移动的胶体，而该模型包含了类似于对流的趋化运动项来表示趋化迁移。实验观察与模型预测之间的一致性支持以下断言：(1) 在界面处发生的弥散诱导的相邻导电区之间的微生物转移发生在界面处，并且对可渗透层的主体流动中的细菌输运影响很小；(2) 趋化实验中相对于非趋化对照的增强的横向细菌迁移主要归因于向化学源区的定向迁移。基于参数敏感性分析，在主体水溶液中确定的趋化参数足以预测我们中间尺度多孔介质系统中的微生物输运。此外，吸附系数值的分析支持了先前研究的观察结果，即趋化剂梯度的影响可能会降低微生物在多孔介质表面的沉积。通过定量描述非均质系统中的细菌输运和分布，该数学模型有助于深入了解颗粒介质系统中的趋化作用和运动效应，并为原位微生物过程中微生物输运的建模提供了思路。
