DESIGN AND PERFORMANCE OF BIOFILTERS FOR THE REMOVAL OF ALKYLBENZENE VAPORS

Three identical biofilters, run under the same conditions but inoculat ed with different mixed cultures, were fed a mixture of toluene, ethyl benzene, and o-xylene (TEX) gases. Inert porous perlite was used as su pport material, in contrast to the more conventional biofiltration sys tems where natural supports are used. Biodegradation started in all th ree biofilters a few hours after inoculation, without previous adaptat ion of the inocula to the toxic mixture. Despite acidification of the systems to pH values below 4.5, the elimination capacities reached wer e fully satisfactory. The best performing biofilter, in which bacteria were dominant, showed an elimination capacity of 70 g TEX m(-3) h(-1) with a near complete removal of the mixture up to an influent concent ration of 1200 mg TEX m(-3) at a gas residence time of 57 s. Most of t he ingoing carbon was recovered as carbon dioxide in the outgoing gas. In the other biofilters fungi dominated and performance was slightly worse. With single substrates, the elimination capacity was higher for toluene and ethylbenzene than for the TEX mixture, whereas o-xylene r emoval was slowest in all cases. Also when feeding the mixture to the biofilters, o-xylene was removed most slowly.