Measurement of flow field in biofilm reactors by 3-D magnetic resonance imaging

3-D Magnetic resonance imaging (MRI) was used to measure the flow field of water in a packed-bed column containing Serratia sp. biofilm supported on polyurethane foam, and subsequently to follow a reaction which precipitates lanthanum phosphate on the biofilm. Sensitizing the MR image contrast to the fluid flow along the axis of the bioreactor provided better image-contrast between the foam and fluid compared to that based on MR signal intensity alone. After reaction, that same "velocity contrast" effectively defined the difference between blocked and unblocked regions by distinguishing between regions of flow and no flow. Data acquired during progressive blockage of reactors challenged at two different flow rates accord with reactor theory; thus, the faster flow rate replenished the reactants uniformly, whereas at the slower flow rate the reactants were concentration limited. MRI velocimetry was used to generate data that can be used to model reactors where the efficiency is progressively compromised by blockage due to precipitation. (c) 2005 American Institute of Chemical Engineers.