BACTERIAL CLOGGING OF POROUS-MEDIA - A NEW MODELING APPROACH

A comparison is made between existing mathematical models and experimental data that relate the reduction of the saturated hydraulic conductivity (K) of a porous medium to the porosity reduction caused by microbial growth. The models yielded a realistic prediction of a data set obtained with a model porous medium consisting of millimeter-size glass spheres, but failed to predict the clogging behaviour observed in smaller-than-1-mm sand. A new modelling approach, semi-mechanistic in nature, is proposed that gives good predictions of fine sand media as well. It relaxes the assumption about uniformly-thick biofilms by allowing a second arrangement to occur, i.e, discrete plugs filling the pore lumen. The new model requires input data on two intrinsic properties of the system, which renders it sufficiently flexible as to fit very different data sets. The two model parameters are K-min, the minimum K value when all porosity is filled with microorganisms, and B-c, the biovolume fraction at which most cell detachment from biofilm occurs.