Trickle-bed air biofilters (TBABs) are suitable for treating volatile organic compounds (VOCs) at a significantly high practical loading because of their controlled environmental conditions. The application of TBAB for treating styrene-contaminated air under periodic backwashing and cyclical nonuse periods at a styrene loading of 0.64 -3.17 kg chemical oxygen demand (COD)/m 3 ⅐day was the main focus of this study. Consistent long-term efficient performance of TBAB strongly depended on biomass control. A periodic in situ upflow with nutrient solution under media fluidization, that is, backwashing, was approached in this study. Two different nonuse periods were employed to simulate a shutdown for equipment repair or during weekends and holidays. The first is a starvation period without styrene loading, and the second is a stagnant period, which reflects no flow passing through the biofilter.For styrene loadings up to 1.9 kg COD/m 3 ⅐day, removal efficiencies consistently above 99% were achieved by conducting a coordinated biomass control strategy, that is, backwashing for 1 hr once per week. Under cyclical nonuse periods for styrene loadings up to 1.27 kg COD/m 3 ⅐day, stable long-term performance of the biofilter was maintained at more than 99% removal without employing backwashing. No substantial impact of nonuse periods on the biofilter performance was revealed. However, a coordinated biomass control by backwashing subsequently was unavoidable for attaining consistently high removal efficiency at a styrene loading of 3.17 kg COD/m 3 ⅐day.As styrene loading was increased, reacclimation of the biofilter to reach the 99% removal efficiency following backwashing or the nonuse periods was delayed. After the nonuse periods, the response of the biofilter was a strong function of the biomass in the bed. No significant difference between the effects of the two different nonuse periods on TBAB performance was observed during the study period.

A laboratory-scale trickle-bed air biofilter was evaluated for the removal of methyl isobutyl ketone ͑MIBK͒ from a waste gas stream. Six-millimeter ͑6 mm͒ Celite pellets ͑R-635͒ were used as the biological attachment medium. Effects of MIBK volumetric loading rates on removal efficiency, biofilter reacclimation, biomass growth, and removal kinetics were studied under three different operating conditions, namely, backwashing and two intermittent periods ͑off chemical-no MIBK input; and off flow-no flow input͒. Backwashing of the biofilter once a week with full-medium fluidization removed the excess biomass and attained stable long-term performance with over 99% removal efficiency for loading rates less than 3.26 kg chemical oxygen demand ͑COD͒ /m 3 day. The two intermittent periods could also sustain high removal efficiency for loading rates up to 1.09 kg COD/ m 3 day without any backwashing. The recovery time increased with an increase in loading rates. Furthermore, the intermittent operations required a longer time to recover than backwashing. The pseudo-first-order removal rate constant decreased with an increase in volumetric loading rate. The removal kinetics showed an apparent dependency on the experimental operating conditions.

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(backwashing, starvation, and stagnant). Because the biofilter response was strongly dependent on the active biomass in the system, biofilter response after the non-use periods was significantly different from that after backwashing.

A trickle‐bed air biofilter (TBAB) was evaluated under conditions of interchanging the feed volatile organic compounds (VOCs) in the sequence methyl ethyl ketone (MEK), toluene, methyl isobutyl ketone (MIBK), styrene, and then back to MEK. The obtained performance results revealed that the biofilter provided high removal efficiency within the critical loading of each VOC, which was previously defined in the non‐interchanging VOC fed biofilter. The biofilter easily acclimated to the oxygenated compounds (MEK and MIBK), but re‐acclimation was delayed for the aromatic compounds (toluene and styrene). Ratios of the molar mass of CO2 produced per molar mass of VOC removed were investigated. It has been found that the ratios for the aromatic compounds closely resembled the theoretical complete chemical oxidation based ratios while larger differences were encountered with the oxygenated compounds. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes was used to assess the impact of interchanging VOCs on the bacterial community structure in the biofilter. The results from denaturing gradient gel electrophoresis (DGGE) showed that the structure of the microbial community in the biofilter was different after each interchange of VOCs.