Interaction of acrylonitrile vapors on a bench scale biofilter treating styrene-polluted waste gas streams

ABSTRACT

Considering concurrent use of styrene and acrylonitrile as raw materials in the production of synthetic resins and plastic and their associated differences in physiochemical properties and biodegradability, our experiments were conducted in a three-stage downflow bench-scale biofilter to study the potential suppressive effects of acrylonitrile on styrene removal. A Mixture of yard waste compost and shredded plastics and activated sludge was used as bed media. Gas phase concentration of styrene and acrylonitrile was determined via gas chromatographic analysis. Under steady-state conditions, maximum elimination capacity of styrene and acrylonitrile was 44 and 120 g/m[3] h, respectively. The effect of moisture was very significant in reducing the specific adsorptive capacity [microg/g of bed media] of styrene and acrylonitrile. The bed media with 60% moisture content lost styrene absorption capacities by more than one order of magnitude when compared to dry media. The existence of water increased the absorption capacity of medium for acrylonitrile about 95%. Styrene elimination capacity of the biofilter during co-treatment was less as compared to pure styrene biodegradation indicating the likelihood of inhibitory kinetics. Introduction of acrylonitrile into the air stream reduced elimination capacity of styrene to 103 g/m[3] h. The adverse impact on removal rate of acrylonitrile due to the presence of styrene in the gas stream was minimal. Carbonequivalent removal for the system amounted to about 85 g C/m[3] h at empty bed retention time of 120 s