Factors affecting soluble selenium removal by a selenate-reducing bacterium Bacillus sp. SF-1

Area of Science:

• Environmental Microbiology
• Bioremediation
• Toxicology

Background:

• High concentrations of soluble selenium (selenate and selenite) pose significant environmental and health risks due to their acute and chronic toxicity.
• Developing effective biological methods for selenium removal from contaminated water sources is crucial.

Purpose of the Study:

• To investigate the parameters influencing the reductive transformation of selenate and selenite into elemental selenium by Bacillus sp. strain SF-1.
• To assess the feasibility of using Bacillus sp. SF-1 for biological selenium removal from wastewater.

Main Methods:

• Culturing Bacillus sp. strain SF-1 under various conditions to study selenium reduction.
• Analyzing the effects of carbon source, oxygen availability, and substrate concentration on the reduction rates.
• Testing the impact of co-existing oxyanions on the selenium transformation process.
• Developing and evaluating a model sequencing batch reactor for selenium removal.

Main Results:

• Bacillus sp. SF-1 efficiently reduced 20 mM selenate to selenite and 2 mM selenite to elemental selenium anaerobically with a suitable carbon source.
• Selenate reduction proceeded faster than selenite reduction, leading to transient selenite accumulation.
• Elemental selenium was observed both intracellularly and extracellularly.
• The strain utilized various organic acids and sugars as carbon sources.
• Sulfate did not inhibit the process, but nitrate completely inhibited it.
• A sequencing batch system demonstrated effective selenium removal from selenate-rich wastewater.

Conclusions:

• Bacillus sp. strain SF-1 is a robust candidate for bioremediation of selenium-contaminated environments.
• Optimized anaerobic conditions and appropriate carbon sources enhance selenium removal efficiency.
• The developed sequencing batch system shows practical applicability for industrial wastewater treatment.