In recent decades, biofiltration has been widely accepted for the treatment of contaminated air stream containing low concentration of odorous compounds or volatile organic compounds (VOCs). In this study, conventional biofilters packed with flexible synthetic polyurethane (PU) foam carriers were operated to remove toluene from a contaminated air stream. PU foams containing various amounts of pulverized activated carbon (PAC) were synthesized for the biofilter media and tested for toluene removal. Four biofilter columns were operated for 60 days to remove gaseous toluene from a contaminated air stream. During the biofiltration experiment, inlet toluene concentration was in the range of 0-150 ppm and EBRT (i.e., empty bed residence time) was kept at 26-42 seconds. Pressure drop of the biofilter bed was less than 3 mm H2O/m filter bed. The maximum removal capacity of toluene in the biofilters packed with PU-PAC foam was in the order of column II (PAC = 7.08%) > column III (PAC = 8.97%) > column I (PAC = 4.95%) > column IV (PAC = 13.52%), while the complete removal capacity was in the order of column II > column I > column III > column IV. The better biofiltration performance in column II was attributed to higher porosity providing favorable conditions for microbial growth. The results of biodegradation kinetic analysis showed that PU-PAC foam with 7.08% of PAC content had higher maximum removal rate (Vm = 14.99 g toluene/kg dry material/day) than the other PU-PAC foams. In overall, the performance of biofiltration might be affected by the structure and physicochemical properties of PU foam induced by PAC content.

The treatment of styrene vapor was carried out using the biofilter packed with loess/polyurethane composite during continuous operation of 74 days. The microorganisms were adapted within 2-3 days under the experimental conditions of inlet concentration and empty bed contact time (EBCT). At 200 sec of EBCT, the removal efficiency of styrene was 100% with 200 ppmv of inlet concentration, while 92% with 400 ppmv of inlet concentration. The biofilter showed the stable removal efficiencies of over 74 % under the EBCT range from 300 to 75 sec at the 150 ppmv of inlet styrene concentration. The maximum capacity of styrene removal for the biofilter packed with loess/polyurethane was 29 g/m3/hr. During continuous operation of 74 days, pH of the drain water changed slightly and the pressure drop through the biofilter column was below 45 mmH2O/m.

A biofiltration system using activated carbon/polyurethane composite as solid support inoculated with Bacillus sp. was developed for treating a gaseous stream containing high concentrations of H2S. The effects of operating condition such as the influent H2S concentration and the empty bed contact time (EBCT) on the removal efficiency of H2S were investigated. The biofilter showed the stable removal efficiencies of over 99 % under the EBCT range from 15 to 60 sec at the 300 ppmv of H2S inlet concentration. When the inlet concentration of H2S was increased, the removal efficiencies decreased, reaching 95 and 74%, at EBCTs of 10 and 7.5 sec, respectively. The maximum elimination capacity in the biofilter packed with activated carbon/polyurethane composite media was 157 g/m3/hr.