Relative humidities of between 95% and 100% were routinely and continuously achieved during the operation. In the continuous experiment, H2S gas at different concentrations was supplied to the column at a flow rate of 36, 72, or 150 L/h. The effect of temperature and flow rate on the removal efficiencies of the biofilter was studied in the ranges of
20-37 °C and 36-150 L/h, respectively. The numbers of microorganisms in the upper and middle layers of the glass column were counted. In addition, the products resulting from the metabolization of H2S by P. putida CH11 were also measured during the continuous experiment.