BIOFILTRATION OF TOLUENE VAPOR UNDER STEADY-STATE AND TRANSIENT CONDITIONS - THEORY AND EXPERIMENTAL RESULTS

Removal of toluene vapor from airstreams was studied in a vapor phase biological reactor known as a biofilter. The reactor was packed with a mixture of peat and perlite particles on which a mixed microbial popu lation (consortium) was immobilized and formed a biolayer. The reactor was operated over a period of 11 months under various inlet-airstream toluene concentrations and flow rates of the contaminated airstream. Except at start-up, no supplemental nutrients were provided to the col umn, which remained active and never exhibited any significant pressur e drop build-up, The process was modeled with general mass balance equ ations which take into account reaction, mass transfer, and adsorption of the pollutant onto the packing material. The model equations were solved numerically and the predicted concentration profiles agreed ver y well with the experimental data, for both steady-state and transient operation. Predicted concentration profiles for the biofilm indicate that toluene gets depleted before oxygen in a thin layer of the order of 35 mu m. This finding is opposite to what has been reported for hyd rophilic solvents where oxygen is depleted before the contaminant in t he biolayer. The model equations have been used in parameter sensitivi ty studies that have revealed the parameters which need to be accurate ly known for predicting the performance of a biofilter.