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WWRC 97-05cc
A Network Model For Biofilm Growth and Its Effects in Porous Media


A new technique for controlling pollution in groundwater is the use of biofilms. Biofilms are bacteria that link themselves with extracellular polymeric substances. The bacteria, already present in the porous or injected into the porous medium, are used to either destroy the contaminant or to plug the medium by forming biobarriers, and, thus limiting the spread of the pollutant.

We present a network model for the SCALE-UP of flow, transport and biofilm growth in porous media. We will start with calculations in straight tubes of different diameters and will link them into rectangular arrays. These arrays of tubes with random diameters simulate the porous medium in two dimensions. Cubic arrays are used in three dimensions. The tubes are subdivided into cells and a new scheme based on upwinded finite differences is used to control numerical diffusion. As the pollutant is transported the bacteria will consume it and grow. This bacterial growth changes the diameter of the tubes and therefore the flow and transport properties of the whole network. Relations between amount of bacteria present and macroscopic properties of the medium, such as permeability and porosity, are derived.

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