Removal characteristics of h₂s by thiobacillus novellus ch 3 biofilter in autotrophic and mixotrophic environments

Abstract

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 mixotrophic environment, but only 97.5% was eliminated in an autotrophic environment. Moreover, the mixotrophic 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.

Key words:

• Hydrogen Sulfide
• Biofilter
• Immobilized Cell
• Thiobacillus novellus