BACTERIAL CLOGGING OF POROUS-MEDIA - A NEW MODELING APPROACH

A comparison is made between existing mathematical models and experime ntal data that relate the reduction of the saturated hydraulic conduct ivity (K) of a porous medium to the porosity reduction caused by micro bial growth. The models yielded a realistic prediction of a data set o btained with a model porous medium consisting of millimeter-size glass spheres, but failed to predict the clogging behaviour observed in sma ller-than-1-mm sand. A new modelling approach, semi-mechanistic in nat ure, is proposed that gives good predictions of fine sand media as wel l. It relaxes the assumption about uniformly-thick biofilms by allowin g a second arrangement to occur, i.e, discrete plugs filling the pore lumen. The new model requires input data on two intrinsic properties o f the system, which renders it sufficiently flexible as to fit very di fferent data sets. The two model parameters are K-min, the minimum K v alue when all porosity is filled with microorganisms, and B-c, the bio volume fraction at which most cell detachment from biofilm occurs.