Substrate Flux into Biofilms of any Thickness

A kinetic model is developed for determining substrate flux into biofilms with known thicknesses, even though the thickness may be of nonsteady state. The critical contribution of this model is that mass transport resistance is explicity included in order that the flux becomes a direct function of the bulk substrate concentration. Laboratory-scale, column reactors were utilized to culture steady-state biofilms of known thicknesses. Subsequently, the influent flow rate or substrate concentration was changed to determine the short-term kinetics of substrate utilization of biofilms of known thicknesses. The model successfully predicted the column performance, except for cases in which oxygen depletion caused dual-substrate limitation. Removal of substrate to very low levels was only possible during short-term experiments when the biofilm was in net decay.