EXPERIMENTAL AND CONCEPTUAL STUDIES ON MASS-TRANSPORT IN BIOFILMS

It is demonstrated that the flow velocity distributions in a flat plate reactor with and without biofilm are considerably different. Flow velocity profiles perpendicular to the channel wall indicate water movement in the space occupied by the biofilm. The flow velocity does not reach zero at the biofilm surface. Water flows through the pores in the biofilm causing convective mass transport. Longitudinal profiles of the flow velocity indicate that the presence of the biofilm disturbs the flow, which increases the entry length required for fully developed viscous flow to be established. Recently it has been shown that biofilms consist of cell clusters separated by interstitial voids. This newly proposed concept of biofilm structure helps to explain these experimental observations. However, the hydrodynamics and mass transport in biofilm systems appear to be more complex than previously assumed.