Simultaneous biodegradation of methane and styrene in biofilters packed with inorganic supports: Experimental and macrokinetic study

Four upflow 0.018 m3 biofilters (3 beds), B-ME, B-200, B-500 and B-700, all packed with inorganic materials, were operated at a constant air flow rate of 0.18 m3 h−1 to eliminate methane (CH4), a harmful greenhouse gas (GHG), and styrene (C8H8), a carcinogenic volatile organic compound (VOC). The biofilters were irrigated with 0.001 m3 of recycled nutrient solution (NS) every day (flow rate of 60 × 10−3 m3 h−1). Styrene inlet load (IL) was kept constant in each biofilter. Different CH4-ILs varying in the range of 7–60 gCH4 m−3 h−1 were examined in B-ME (IL of 0 gC8H8 m−3 h−1), B-200 (IL of 9 gC8H8 m−3 h−1), B-500 (IL of 22 gC8H8 m−3 h−1) and B-700 (IL of 32 gC8H8 m−3 h−1). Finally, the effect of C8H8 on the macrokinetic parameters of CH4 biofiltration was studied based on the Michaelis-Menten model. Average C8H8 removal efficiencies (RE) varying between 64 and 100% were obtained at CH4-ILs increasing from 7 to 60 gCH4 m−3 h−1 and for C8H8-ILs range of 0–32 gC8H8 m−3 h−1. More than 90% of C8H8 was removed in the bottom and middle beds of the biofilters. By increasing C8H8-IL from 0 to 32 gC8H8 m−3 h−1, maximal EC in Michaelis-Menten model and macrokinetic saturation constant declined from 311 to 39 g m−3 h−1 and from 19 to 2.3 g m−3, respectively, which confirmed that an uncompetitive inhibition occurred during CH4 biofiltration in the presence of C8H8.