Biotrickling filtration of airborne styrene: A comparison of filtration media

Abstract

ABSTRACTThis study compares the performances of fern and plastic chips as packing media for the biofiltration of a styrene-laden waste gas stream emitted in a plant for the manufacture of plastic door plates. Fern chips (with a specific surface area of 1090 m2 m−3) and plastic chips (with a specific surface area of 610 m2 m−3) were packed into a pilot-scale biotrickling filter with a total medium volume of 50 L for the performance test. Field waste gas with styrene concentrations in the range of 161–2390 mg Am−3 at 28–30 °C) was introduced to the bed and a fixed empty-bed retention time (EBRT) of 21 sec, a volumetric gas flow rate of 8.57 m3 hr−1, and superficial gas velocity of 53.6 m hr−1 were maintained throughout the experimental period. Nutrients containing metal salts, nitrogen, phosphorus, and milk were supplemented to the filters for maintaining the microbial activities. Results reveal that the biotrickling filter developed in this study had the highest styrene monomer (SM) elimination capacities (170 g m−3 hr−1 for fern-chip packing and 300 g m−3 hr−1 for plastic-chip packing) among those cited in the literature. The plastic medium is a favorable substitute for endangered fern chips. The thermal-setting nature of plastic chips limits their recycle and reuse as raw materials, and the study provides an opportunity for the utilization of the materials.Implications: Biotreatment of contaminants in air streams offers an inexpensive and efficient alternative to conventional technologies. Biofiltration has a great potential for the degradation of gas-borne styrene and total hydrocarbon (THC) removal efficiency of around 80%. The objective of this research was to compare the performances of fern chips and a kind of plastic chips as packing media for biofiltration of the styrene-laden waste gas stream emitted from cutting operations of stripes of premixed unsaturated polyester (UP) and styrene paste before hot-pressing operations for making plastic door plates. From a practical point of view, the plastic medium can be a good substitute medium for fern chips, which has been declared as a protected plant. This study provides an experimentally verified model for the design and operation of such biotreatment systems.