H2S Removal Rate in Continuous Operation. Fluctuation in inlet hydrogen sulfide concentration was examined in the range from 10 to 60 ppm at flow rates of 36 and 72 L/h. The H2S removal efficiency was calculated from the difference in inlet and outlet concentrations. The H2S removal efficiency in the immobilized P. putida CH11 biofilter with or without carbon (glucose) supply at a flow rate of 36 L/h is shown in Figure 4a. The changes in pH and cell number of the biofilter are
shown in Figure 4b. The biofilter showed good operational efficiency regardless of whether the flow rate was 36 or 72 L/h (data not shown). At a flow rate of 36 L/h, the average removal efficiency of the biofilter with glucose supply was 97.1% for hydrogen sulfide concentrations ranging from 10 to 60 ppm. When the flow rate was increased to 72 L/h, the average removal efficiency was 95.8%. Such a high removal efficiency lasted for 3 months (data not shown). By contrast, the high H2S removal efficiency lasted for only 3 days at 36 L/h in the absence of glucose.