Removal of styrene and acrylonitrile mixture in a gas phase bench scale biofilter

Abstract

Styrene and acrylonitrile are produced in large quantities in the petrochemical industries and have been listed among the 189 hazardous and toxic atmospheric contaminants under United States Clean Air Act Amendments 1990 due to their adverse effects on human health. The experimental work was conducted to evaluate the inhibition effect of biofilter in the presence of co-substrate. Yard waste compost mixed with shredded hard plastics in a 25:75 v/v ratio of plastics:compost as the bed media was inoculated with thickened municipal activated sludge. Acclimation to styrene was achieved at 45 days, but there was a very short acclimation period for acrylonitrile. The results show that performance of biofilter with mixed cultures is better than single strains. Finally application of activated sludge for start up of biofilters in full scale would be practical and economical. Under steady-state conditions, maximum elimination capacity of pure styrene was obtained 44 g m-3 h-1 but introducing acrylonitrile into the air stream adversely impacted the performance of biofilter in the reduction of styrene. Maximum elimination capacity of 103 g m-3 h-1 obtained for acrylonitrile at the presence of styrene whereas the maximum removal rate of 120 g m-3 h-1 acquired for pure acrylonitrile. Removal of acrylonitrile was not affected by the presence of styrene in the air stream. The biofilter removed up to about 85 g carbon m-3 h-1 at empty bed retention times between 30 and 120 s.