Effect of biofilm growth on steady-state biofilm models.

The results of numerical simulations for a growing biological film are presented to justify the use of steady-state biofilm models for approximating the behavior of both unlimited and shear-limited biofilms. For an unlimited biofilm we show that although the total biofilm thickness may continue to increase over time, the active biofilm volume will reach a constant value. We also show that the profile of active microorganisms within the biofilm will become constant with respect to the biofilm/fluid interface and simply move outward as the biofilm thickness increases. For a shear-limited biofilm we similarly show that once a "limiting" thickness has been reached the active biofilm volume, substrate consumption, and profile of active microorganisms within the biofilm will also be independent of the biofilm thickness.