Modelling and analysis of membrane-attached biofilms

The theory of diffusion and reaction has been applied to describe mass tran sfer and reaction phenomena in membrane-attached biofilms (MABs) growing in extractive membrane bioreactors (EMBs), and to establish the rate-limiting mechanisms in these systems. The model formulated accounts for substrate c ounter-diffusion and two-limiting-substrate reaction within the biofilm. Mo del simulations are compared to experimental data obtained in a lab-scale E MB and a simple case study is considered to show how MABs affect performanc e of EMBs. It is found that the organic substrate flux across the membrane is strongly affected by MABs, which constitute an additional resistance to mass transfer and in most cases reduce the flux across the membrane. As a r esult of the investigation, it is concluded that the decrease of flux in th e presence of MABs, observed experimentally and predicted theoretically, is dominated by the resistance to organic substrate transfer caused by the bi ofilm.