Macro-scale modeling concepts for bacterial growth and transport in advective two-phase porous media systems

多孔介质为细菌提供了极好的生存条件，因为它们的栖息地受到保护，但仍然允许持续的营养供应。因此，微生物的存在对许多环境和工程多孔介质系统做出了重大贡献。当这些多孔介质系统用于工程或工业应用时，了解流动、运输和微生物过程之间的相互作用是很重要的。文献中存在多种建模方法，但它们主要是针对单相多孔介质系统而开发的。此外，由于多孔介质的不透明性质使得很难观察和理解发生在孔隙中的细菌过程(例如附着/脱离和生物膜的形成)，这些过程还没有被充分了解。在这个项目中，两个玻璃板之间的人工多孔结构被称为玻璃-硅-玻璃微模型，将被用来研究细菌在两相饱和的多孔介质中的行为。这些透明的准二维微观模型允许通过微观分析直接观察细菌的生长、运输和附着/脱离等过程。用于实验室实验的细菌属于产甲烷古生菌。通过图像处理对实验结果的详细解释将允许产生细菌计数及其结构和运动的空间和时间分辨数据。基于这些数据集，将开发一个描述细菌在两相多孔介质系统中生长和运动的改进的数学模型。该模型旨在考虑细菌在非营养限制条件下的生长、不同细菌结构(浮游生物和生物膜)的存在、它们各自的运输特性以及附着和脱离过程。为了对新模型进行检验和参数化，将基于对角隐式Runge-Kutta时间离散化方法进行数值实现，该方法非常适合包含强非线性源项。该理论模型的应用致力于微生物地下甲烷化技术，该技术导致注入的氢气和二氧化碳通过密集的细菌反应转化为甲烷。

Porous media provide excellent living conditions for bacteria because their habitat is protected but still allows a continuous nutrient supply. As a consequence, microorganisms exist and make a substantial contribution to many environmental and engineered porous media systems. When these porous media systems are used for engineered or industrial applications it is important to understand the interaction between flow, transport and microbiological processes. A variety of modeling methods exists in the literature, but they were predominantly developed for single-phase porous media systems. Since, in addition, the opaque nature of porous media makes it difficult to observe and understand bacterial processes which occur in the pores (e.g. attachment/detachment and formation of biofilms), these processes are insufficiently understood.In this project artificial porous structures between two glass plates, referred to as glass-silicon-glass micromodels, will be applied to investigate the behavior of bacteria in porous media saturated by two phases. These transparent quasi two-dimensional micromodels allow the direct observation of bacterial processes, as e.g. growth, transport, and attachment/detachment, by microscopic analysis. The bacteria used for laboratory experiments belong to the class of methanogenic archaea. The detailed interpretation of the experimental results by image processing will allow to generate spatially and temporally resolved data of bacterial counts and their structure and movement. An improved mathematical model describing the bacterial growth and movement in two-phase porous media systems will be developed based on these data sets. The model intends to consider the bacterial growth under non-nutrient limited conditions, the existence of different bacterial structures (plankton and biofilm), their individual transport properties and attachment and detachment processes. For testing and parametrizing the newly developed model, it will be numerically implemented based on a diagonally implicit Runge-Kutta time discretization method which is well suited to incorporate the strong non-linear source terms.The application of the theoretical model is devoted to the technology of microbial underground methanation, which leads to the transformation of the injected hydrogen and carbon dioxide to methane by intensive bacterial reactions.