: Air bioÐltration is now under active consideration for the removal of the volatile organic compounds from air polluted streams. In order to investigate the performance of this newly developed technology, a bioÐltration pilot unit was operated for a continuous period of 8 months. The bioÐlter column was packed with commercially conditioned peat. At start-up, the Ðlter bed was inoculated with four species of microorganisms. The resulting bioÐlter was fed with air contaminated with toluene, xylene or a mixture of toluene and xylene. The maximum elimination capacities attained were 165 g m~3 h~1 for toluene, 66 g m~3 h~1 for xylene and 115 g m~3 h~1 for the mixture of toluene and xylene. These speciÐc performances exceed the values published in the technical and commercial literature for similar processes. Xylene isomers were degraded in decreasing order of reactivity, m-xylene, p-xylene, o-xylene. In the case of air polluted with a toluene and xylene mixture, it was noticed that the metabolism of toluene biodegradation was inhibited by the presence of xylene. Characterization of the bioÐlm microbial populations after several weeks of operation showed that the dominant strains among the isolated culturable strains from the bioÐlm, even if di †erent from the initially inoculated strains, had at least one physiological property favoring degradation of aromatic organic rings. The performance of the bioÐlter was found to be dependent on the temperature of the Ðlter media and the pressure drop through the bed. Finally, a steady state mathematical model was tested in order to theoretically describe the experimental results. This model is used to illustrate the operating di †usion and reaction regimes at steady state for the case of each pollutant.

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Experiments during a period of 93 days are reported on the treatment of waste air containing toluene vapor using a laboratory scale biofilter system packed with peat inoculated with specific florae (Pseudomonas type) and intermittently humidified with a nutrient solution necessary for the survival of the micro-organisms. Design and operation parameters were regularly measured in order to check the performance of the biodegradation process.Under

A laboratory scale biofilter system was used to eliminate toluene and ethanol, the main solvents employed in lacquering, from waste air. A specific micro-flora (mixture of Bacillus for ethanol and two pseudomonas species for toluene) able to degrade ethanol and toluene, was jimed on a packed bed of particles of commercial peat intermittently humidified by a nutrient solution necessary for the suroival of the micro-organisms.In the experiments, polluted gas was fed upwara3 through the bed and pbysical parameten: moisture content ofpat; humidity of aic temperature; pressure drop; inlevoutlet concentration of gas and microbialpopulation were measured regularly in order to check the performance of the biodegradation process.These experiments showed good pe~ormance and good stability of the biofilter over time.

Biofiltration is a cleaning technique for waste air contaminated with some organic compounds. The advantages of the conventional biofilter over other biological systems are a high-superficial area best suited for the treatment of some compounds with poor water solubility, ease of operation, and low operating costs. It has crucial disadvantages, however; for example, it is not suitable to treat waste gases with high VOC concentrations and it has poor control of reaction conditions. To improve on these problems and to build a high-performance biofilter, three structured peat media and two trickling systems have been introduced in this study. The influences of media size and composition have been investigated experimentally. Peat bead blended with 30% (w/w) certain mineral material with a good binding capacity has advantages over other packing materials, for example, suitable size to prevent blockage due to microbial growth, strong buffering capacity to neutralize acidic substances in the system, and a pH range of 7.0-7.2 suitable for the growth of bacteria. Dropwise trickling system offers an effective measure to easily control the moisture content of the bed and the reaction conditions (pH, nutrient) and to partially remove excess biomass produced during the metabolic processes of microorganisms. The influence of nutrient supplementation has also been investigated in this study, which has revealed that the biological system was in a condition of nutrient limitation instead of carbon limitation. The biofilters built in our laboratory were used to treat waste gas contaminated with toluene in a concentration range of 1 to 3.2 g/m and at the specific gas flow rate of 24 to120 m/m.hr. Under the conditions employed, a high elimination capacity (135 g/m.hr) was obtained in the biofilter packed with peat beads (blended with 30% of the mineral material), and no blockage problem was observed in an experimental period of 2-3 months.