PERFORMANCE OF A STYRENE-DEGRADING BIOFILTER CONTAINING THE YEAST EXOPHIALA-JEANSELMEI

A general mathematical model developed for a description of pollutant degradation in a biofilm was used to evaluate the performance of a bio filter for the purification of styrene-containing gas. The biofilter c ontained perlite as an inert support on which a biofilm was present co mposed of a mixed microbial population containing the fungus Exophiala jeanselmei as a major styrene-degrading microorganism. Although styre ne is a moderately hydrophobic compound, the biofilter was reaction li mited at a styrene gas phase concentration of 0.1-2.4 g/m(3). Limitati on of biofilter performance by the mass transfer of styrene was only o bserved at styrene concentrations lower than 0.06 g/m(3). A maximal st yrene degradation rate of 62 g/(m(3) . h) was maintained for over 1 ye ar. At a high styrene concentration, the maximal styrene degradation r ate could be increased to 91 g/(m3 . h) by increasing the oxygen conce ntration in the gas from 20 to 40%. After 300 days of operation, the d ry-weight biomass concentration of the filter bed was 41% (w/w), and a n average biofilm thickness of 240-280 mu m, but maximal up to 600 mu m, was observed. Experimental results and model calculations indicated an effective biofilm thickness of about 80 mu m. It is postulated tha t the thickness of the effective biofilm is determined by the oxygen a vailability in the biofilm. (C) 1997 John Wiley & Sons, Inc.