Seminar: How biofilm-colonizing media affect hydraulic parameters

Biofilm colonize porous media under certain conditions, leading to partial clogging of the pore network. This growth affects only minorly accessible porosity, but this has strong implications in changes in hydraulic parameters as a function of the degree of clogging. The impact upon reduction of hydraulic conductivity has been widely reported in the literature and modeled. This is quite different for the reported order(s) of magnitude increase in dispersion coefficient derived from tracer tests. We develop here simple yet practical expressions for the evaluation of apparent dispersion coefficients caused by biomass colonization, based on the modification of the reported breakthrough curves (in terms of temporal moments) with respect to the biofilm-free porous media. These expressions are written in terms of observables that are relatively easy to measure in the lab or the field, contrarily to existing expressions based on a bundle of capillary tubes. We have tested our simplified expression in a number of reported sites, where enhanced dispersion values of 1-2 orders of magnitude have been reported.