Operation of biofilters : a numerical approach to some couplings between hydrodynamic and biofilm growth Modeling

Abstract : Solute transport coupled with biofilm growth in porous media is encountered in many engineered applications, for instance biofiltration of wastewater and air pollutant treatment. In terms of modelling, the interaction between biology, hydrodynamic and chemistry are still difficult to understand at the fine scale: that led to a wide dissemination of macroscopic model, simpler to handle. However, one issue consists in providing a macroscopic model complex enough to take into account the relevant processes accounting for the coupling between the biomass development and system functioning, but simple enough for operational use. This thesis focused on few selected processes that influence the macroscopic behavior of such system. First, we investigated the permeability reduction modeling accounting for biofilm development. A model including two features that result in permeability reduction (pore radius reduction and pore plugging) was developed. This model was assessed in a wide range of experimental data. Another part of the thesis focused on the initial biomass attachment that is an important feature to characterize the system initial state. Following the concept that bacterial cell can be treated as soft colloids, a new correlation equation was developed to estimate the bacteria attachment efficiency. This correlation is based on the regression analysis of a wide range of experimental data of colloid deposition in various electrolyte conditions, flowrates and geometries of porous media. New dimensionless parameters have been introduced to represent the coupled effects of Derjaguin-Landau-Verwey-Overbeek (DLVO) forces, hydrodynamic forces and to account for geometry of porous media. These features were introduced in a 1D dimensional model that have been developed for the numerical simulation of solute transport coupled with biofilm growth. An important issue in this model was to properly represent biofilm detachment. Another distinctive feature of our model is an attempt to account for the “sloughing” process in modeling biofilm detachment. Sloughing is a different process than erosion which corresponds to a discrete removal of large fraction of biofilm. In this study, biofilm sloughing has been separately accounted in the numerical modeling porous media bioclogging. Biofilm sloughing was considered as a stochastic process and quantified by random generator. So this discrete events could be incorporated into other continuous processes to determine the biomass transfer from biofilm to the liquid phase. Numerical simulations have been performed using OpenFoam to implement the model. Simulation with and without the sloughing term were performed and discussed in the frame of available literature data
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Hoang Lam Pham. Operation of biofilters : a numerical approach to some couplings between hydrodynamic and biofilm growth Modeling. Organic chemistry. Université Grenoble Alpes, 2018. English. ⟨NNT : 2018GREAI073⟩. ⟨tel-01983040⟩

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