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Description
Porous media provide excellent living conditions for bacteria, as their habitat is protected while still allowing for a continuous supply of nutrients. Consequently, microorganisms exist in many natural and engineered porous media and exert a significant influence there. When these media are used for engineering or industrial applications, it is crucial to understand the interactions between flow, transport, and microbiological processes. A variety of modeling methods exist in the literature; however, these have generally been developed under single-phase flow conditions. It is difficult to observe microbiological processes in the natural and complex pore structures of rocks (such as adhesion/detachment and biofilm formation), and consequently, these processes have been insufficiently studied.
In this project, artificial structures modeled after the pore structures of rock are created and used to investigate the behavior of bacteria in porous media saturated with two phases. These transparent, so to speak two-dimensional micromodels allow for direct observation of microbiological processes, such as growth, transport, and adhesion/detachment of bacteria, through microscopic analysis. The bacteria used in the experimental studies belong to the class of methanogenic archaea. Detailed interpretation of the experimental results through image data processing enables the generation of spatially and temporally resolved datasets for the number, structure, and movement of the bacteria. From these datasets, an improved mathematical model is developed that describes the growth and movement of bacteria in porous media saturated with two phases. The model is intended to account for bacterial growth under non-nutrient-limited conditions, the presence of various bacterial structures (plankton and biofilm), individual movement properties, and the adhesion and detachment processes. To test and parameterize the newly developed model, it is numerically implemented based on a diagonal-implicit Runge-Kutta method, which is well-suited for highly nonlinear source terms.
The application of the theoretical model relates to subsurface methanation technology, in which the injected gas mixture of hydrogen and carbon dioxide is converted into methane through microbiological reactions.
