Isobutyraldehyde as a competitor of the dimethyl sulfide degrading activity in biofilters

Upon inoculation with Hyphomicrobium MS3, the elimination capacity of a lab-scale biofilter for the odorant dimethyl sulfide (Me2S) can be strongly increased from less than 10 to more than 35 and 1000 g m(-3)d(-1) using wood bark and compost as a carrier material, respectively. However, upon supplementation of isobutyraldehyde (IBA) as a second gaseous substrate, sequential degradation profiles of IBA and Me2S in physically separated sections were observed in the Hyphomicrobium MS3-inoculated wood bark and compost biofilters. Contrary to this, the biofiltration efficiency for Me2S remained unaffected upon the supplementation of toluene as a second gaseous substrate. Batch experiments with the liquid Hyphomicrobium MS3 culture confirmed the competitive effect of IBA on the Me2S degrading activity: in the presence of both compounds, Hyphomicrobium MS3 preferred degradation of the carbonyl compound. In technical terms, this means that the complete purification of a waste gas stream containing both IBA and Me2S should be performed using sufficiently high or bistage Hyphomicrobium MS3-inoculated biofilters. Design criteria have to be conceived in this respect.