Abstract
Previously isolated Sphingomonas sp. D3K1 was biofilter (BF) inoculated into composite rock wool-compost packing media and biofiltration of single gas—ethylbenzene in BF1 and o-xylene in BF2—and mixed BTEX compounds in BF3 were investigated. At 62 s EBRT and feed flow rate of 0.14 m3/h, high removal efficiencies of 92.0 ± 2.8%, 92.0 ± 3.1%, and 89.2 ± 1.1% were achieved in BF1, BF2, and BF3, respectively. Decreasing the EBRT to 48 s resulted in lower elimination capacities of the three biofilters, while regular nutrient addition showed an increase in the attainable elimination capacities for ethylbenzene and o-xylene of BF1 and BF2, respectively. Maximum elimination capacities of 34.3 g-ethylbenzene/m3/h (BF1) and 38.6 g- o-xylene/m3/h (BF2) were obtained at 48 s EBRT. For BF3, the maximum elimination capacity was 32.9 g-BTEX/m3/h at 62 s EBRT. In the case of mixed BTEX biofilter, o-xylene showed the most significant decrease in the biodegradability when nutrient was insufficient in the system. Sphingomonas sp. D3K1 was more favorable to the removal of toluene when o-xylene was less than 10 g/m3/h, but shifted to benzene when the loading rate of o-xylene was higher than 10 g/m3/h.