The Chemical Technology Division at Oak Ridge National Laboratory has developed the use of fluidized beds as bioreactors (ORNL/MIT 319, 1981). Fluidized beds provide an effective means of promoting contact and hence mass transfer between the fluid and solid phases. The advantages of these features have been demonstrated in biological systems for ethanol production and wastewater treatment. For example, Pseudomonas bacteria adhering to coal particles in a fluidized bed successfully convert wastewater nitrates to nitrogen gas at 20 to 100 times the rate achieved in a stirred-tank bioreactor. Although global reaction rates and operating conditions of fluidized bioreactors have been studied thoroughly, an understanding of their flow patterns is needed to allow modeling and scale-up. From the exit concentration data of a typical run, E(), given below, fit the data with:

(a) The axial dispersion model.
(b) The tanks-in-series model.
(c) A model of your own (Level D).