Biological oxidation of gaseous VOC mixtures in a trickle-bed air biofilter

Two VOC mixtures with different compositions were fed to a Trickle-bed air biofilter with step-change in influent mixture concentrations from 50 ppmv to 1000 ppmv. The empty bed retention time was maintained at 2.02 min. Backwashing was conducted once a week as biomass control. The biofilter maintained 99% overall removal efficiency after start-up when the influent concentration did not exceed 500 ppmv (3.94 kg COD/m³-day) and 300 ppmv (2.41 kg COD/m³-day) for mixture 1 and mixture 2, respectively. Re-acclimation of the biofilter performance was delayed with increase of influent concentration for both mixtures. The reacclimation for mixture 2 as compared to mixture 1 was delayed due to its higher toluene content. Removal behaviors of MEK, MIBK, and styrene along the biofilter depth were similar for both mixtures. However, toluene removal utilized more biofilter depth for mixture 2 as compared to mixture 1.