Removal of mixtures of acetaldehyde and propionaldehyde from waste gas in packed column with immobilized activated sludge gel beads

The removal of mixed acetaldehyde and propionaldehyde as a model of the bin ary contaminants in waste gas was studied in the packed column containing t he immobilized activated sludge gel beads together with the hollow plastic balls developed for the removal of a single aldehyde in the previous work. The rate of each aldehyde biodegradation by the gel beads in the aldehydes mixture was expressed by the Michaelis-Menten type rate equation with an in hibitory term due to the other coexistent aldehyde. The kinetic parameters involved were found to be the same as those determined previously for biode gradation of a single aldehyde. A model for prediction of removal of each a ldehyde in the packed column was developed assuming that each aldehyde diss olved in the aqueous phase within the gel bead was biodegraded according to the above rate equation with no mass transfer effect. The packed column wa s stable and efficient for removal of the binary aldehydes mixture with a v ery low pressure drop for gas flow due to a reduced gel beads bed compactio n by the hollow plastic balls. Removal of each aldehyde decreased with incr easing the inlet aldehyde concentrations since each biodegradation rate its elf approached asymptotically the maximum one with increase in each aldehyd e concentration. The observed removals for each aldehyde in the aldehydes m ixture agreed well with those calculated from the design equations develope d. The contact efficiency of gel beads with the waste gas stream was estima ted to be the same value of 0.24 as in the previous work, supporting that t he efficiency was specific to the geometrical and physical properties of th e packed column used. (C) 2001 Elsevier Science B.V. All rights reserved.