Removal characteristics of H2S by Thiobacillus novellus CH 3 biofilter in autotrophic and mixotrophic environments

Thiobacillus novellus, like other facultative chemoautotrophs, possesses the unique ability to grow autotrophically as well as heterotrophically. Since in nature the bacteria are likely to encounter different environments, i.e., autotrophic, heterotrophic, or mixotrophic conditions, it is of considerable interest to determine the removal characteristics of H2S in different environments. Thiobacillus novellus CH 3 was isolated from piggery wastewater and used to remove H2S gas from air in this study. The results indicated that the Thiobacillus novellus biofilter under mixotrophic conditions possessed broad adaptability of pH (5 - 10) compared to the one under autotrophic conditions. In a batch experiment high H2S concentration (>140 ppm) inhibited the enzymatic activity, thus the H2S removal was limited by the reaction rate rather than the diffusion rate at diluted H2S concentration. During the environmental shock experiment, 99.5% of the H2S content from the inlet was eliminated in a misotrophic environment, but only 97.5% was eliminated in an autotrophic environment. Moreover, the misotrophic biofilter possessed higher removal capacity than the autotrophic biofilter. Thus, the results suggest that the potential of Thiobacillus novellus CH 3 in the mixotrophic environment should be of selective advantage over the cells in the autotrophic environment.