SIFT-MS a novel tool for monitoring and evaluating a biofilter performance

Biofilters are suitable to treat industrial emissions polluted with volatile organic compounds. This study investigates the selected ion flow tube mass spectrometer (SIFT-MS) as a new and fast analysis apparatus to determine the performance, the biokinetic parameters and the external porosity of a biofilter. The SIFT-MS was also used to obtain more information about mass transfer resistance and reaction limitation which can occur in bioreactors. Online analyses were performed on a biofilter packed with a mixture of compost and wooden dowels, treating an air stream contaminated with dimethyl sulphide (DMS), hexane and toluene. Measurements to determine the biokinetic parameters were performed in less than three days to keep the biomass about constant. The Michaelis-Menten half saturation constant, Km, and the maximal volumetric elimination rate, rm, were calculated for the removal of DMS based on measurements at 35, 60 and 90 s empty bed residence time (EBRT). Using pulse injections, the external porosity of the biofilter, 40.2 ± 0.3% could be determined online and information about mass transfer resistance and reaction limitation could be retrieved. Mass transfer resistance becomes significant for compounds with a high Henry coefficient at lower gas velocities.