An analysis of a trickle-bed bioreactor: Carbon disulfide removal

An analysis of the local processes occurring in a trickle-bed bioreactor (T BB) with a first-order bioreaction shows that the identification of the TBB operating regime requires knowledge of the substrate concentration in the liquid phase. If the substrate liquid concentration is close to 0, the rate -controlling step is mass transfer at the gas-liquid interface; when it is close to the value in equilibrium with the gas phase, the controlling step is the phenomena occurring in the biofilm. CS2 removal rate data obtained i n a TBB with a Thiobacilii consortia biofilm are analyzed to obtain the mas s transfer and kinetic parameters, and to show that the bioreactor operates in a regime mainly controlled by mass transfer. A TBB model with two exper imentally determined parameters is developed and used to show how the biore actor size depends on the rate-limiting step, the absorption factor, the su bstrate fractional conversion, and on the gas and liquid contact pattern. U nder certain conditions, the TBB size is independent of the flowing phases' contact pattern. The model effectively describes substrate gas and liquid concentration data for mass transfer and biodegradation rate controlled pro cesses. (C) 1999 John Wiley & Sons, Inc.