An Innovative Process of Simultaneous Desulfurization and Denitrification by Thiobacillus denitrificans

Abstract

Thiobacillus denitrificans, a species of autotrophic facultative anaerobic bacterium, was found to be capable of oxidizing sulfide into elemental sulfur when nitrate was adopted as its electron acceptor and carbon dioxide as its sole carbon source under anoxic conditions. In this way, sulfur was accumulated extracellularly and nitrate was converted into nitrogen gas. Based on these special physiological characteristics, an innovative process of simultaneous desulfurization and denitrification (SDD) was developed to obtain sulfur from sulfide. A strain of T. denitrificans, named D₄, was isolated and used as sulfur producers in this study. The stoichiometric equations of SDD by T. denitrificans were also derived. The key factors affecting this process were investigated through continuous-flow and batch tests. The experimental results indicated that both the sulfide concentration and the ratio of S²⁻/NO₃ ⁻ in the influent are key factors. Their suitable levels are suggested to be controlled less than 300 mg/L and 5/3–5/2, respectively, to achieve a high sulfur conversion degree.

Keywords:

• Thiobacillus denitrificans
• Biological desulfurization
• Sulfur
• Denitrification
• S²⁻/NO₃ ⁻ ratio.

ACKNOWLEDGMENT

This project was financially supported by the National Natural Science Foundation of China (Contract No. 50208006).

Notes

* The amount of sulfide converted into elemental sulfur/influent sulfide ×100%.

* The amount of nitrate reduced/influent nitrate × 100%.

* Amount of sulfide converted into elemental sulfur.

^† Amount of sulfide converted into sulfate.