In this study, the possibility of the removal of isobutyraldehyde and 2-pentanone was investigated in biotrickling filters (BTFs) at higher temperature (52-65• C). First, the biodegradation of isobutyraldehyde and 2-pentanone in activated sludge was proven by batch experiments at 52 and 62• C. In batch experiments isobutyraldehyde was also degraded up to a temperature of 72• C. Thereafter two bioreactors were operated in parallel, one at ambient temperature (BTF25), and one at 52• C (BTF52). Maximum elimination capacities of 97 and 139 g m −3 h −1 were observed in BTF25 and BTF52, respectively, for isobutyraldehyde. Maximum elimination capacities of 53 and 63 g m −3 h −1 were obtained for 2-pentanone in BTF25 and BTF52, respectively. A significant difference was observed in the operational stability of the two reactors. In the reactor at ambient temperature, operational problems such as foam formation, higher biomass accumulation and organic acid production were observed. In the thermophilic reactor these problems did not occur or were less severe.

BACKGROUND: Several sources such as the paper and pulp industry and waste treatment plants emit waste gases containing volatile organic sulfur compounds at elevated temperature. Since cooling the hot gases increases the operational cost of biological reactors, application of thermophilic microorganisms could be a cost-effective solution. The objectives of this study were to investigate the possibility of removal of dimethyl sulfide from waste gases under thermophilic conditions (52• C) in a membrane bioreactor and to examine the long-term stability of the reactor at elevated temperature. The effects of operating conditions such as gas residence time, nutrient supply, temperature decrease and short-term shutdown on elimination capacity were investigated.

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