Effect of Soluble Sulfide on the Activity of Luminescent Bacteria

Abstract

Sulfide is an important water pollutant widely found in industrial waste water that has attracted much attention. S²⁻, as a weak acidic anion, is easy hydrolyzed to HS⁻ and H₂S in aqueous solution. In this study, biological tests were performed to establish the toxicity of sulfide solutions on luminescent bacteria. Considering the sulfide solution was contained three substances—S²⁻, HS⁻ and H₂S—the toxicity test was performed at different pH values to investigate which form of sulfide increased light emission and which reduced light emission. It was shown that the EC₅₀ values were close at pH 7.4, 8.0 and 9.0 which were higher than pH 5 and 10. The light emission and sulfide concentrations displayed an inverse exponential dose-response relationship within a certain concentration range at pH 5, 6.5 and 10. The same phenomenon occurred for the high concentration of sulfide at pH 7.4, 8 and 9, in which the concentration of sulfide was HS⁻ >> H₂S > S²⁻. An opposite hormesis-effect appeared at the low concentrations of sulfide.

Keywords

• sulfide solution
• light emission
• inhibition ratios
• EC<sub>50</sub>
• hormesis-effect