Comparison of autotrophic and mixotrophic biofilters for H2S removal

We demonstrate that the facultative chemoautotroph Thiobacillus novellus CH3 removes hydrogen sulfide (H2S) gas in continuous reactors under nutrient-limiting conditions. Extensive tests including removal characteristics, metabolic products, and removal efficiencies of H2S by T. novellus CH3 were conducted in autotrophic and mixotrophic environments. The optimal pH value and temperature required to remove hydrogen sulfide are found to be pH 7 and 26 degrees C. The biofilter had an H2S removal efficiency greater than 99.5% under the mixotrophic condition after l0-day operation. The results show that the maximum removal rate and saturation constant were 1.9 g S/d per kg bead and 69.2 ppm, respectively. The main metabolic product of H2S oxidation was determined to be sulfate, but the conversion ratio was dependent on the growth environment. These results suggest that the mixotrophic potential of T. novellus CH3 biofilter provides a significant advantage in HS removal over autotrophic biofilters.