Kinetic analysis of Fe3+ reduction coupled with nitrate removal by Klebsiella sp. FC61 under different conditions

Abstract

Klebsiella sp. FC61, a newly found iron-reducing bacterium, has the ability of simultaneously reducing Fe³⁺ and nitrate under different pH and temperature conditions. Based on kinetic equations, the maximum rate of Fe³⁺ reduction was 0.26 mg L⁻¹ h⁻¹ at pH 6.0 and 0.24 mg L⁻¹ h⁻¹ at 30 °C. The maximum rate of nitrate removal was 0.21 mg L⁻¹ h⁻¹ at pH 7.0 and 0.82 mg L⁻¹ h⁻¹ at 35 °C. After 56 h, nitrate was removed completely, coupled with Fe³⁺ reduction, and there was a transient accumulation of nitrite. Fe³⁺ and nitrate reduction followed the selected kinetic equations well. Moreover, the Arrhenius equation further confirmed the reliability of the data under the different temperature conditions. When analyzed using XRD and SEM, a form of crystalline iron oxide with recovered deposits of strain FC61 was observed.