Removal of arsenic by <i>Acidothiobacillus ferrooxidans</i> bacteria in bench scale fixed-bed bioreactor system

In the present study arsenic contaminated simulated water and groundwater was treated by the combination of biological oxidation of tri-valent arsenite [As (III)] to penta-valent arsenate [As (V)] in presence of <i>Acidothiobacillus ferrooxidans bacteria</i> and its removal by adsorptive filtration in a bioreactor system. This method includes the immobilisation of <i>A.ferrooxidans</i> on Granulated Activated Carbon (GAC) capable of oxidising ferrous [Fe (II)] to ferric [Fe (III)]. The Fe (III) significantly converts the As (III) to As (V) and ultimately removed greater than 95% by the bed of GAC, limestone, and sand. The significant influence of Fe (II) concentration (0.1–1.5 gL⁻¹), flowrate (0.06–0.18 Lh⁻¹), and initial As (III) concentration (100–1000 µgL⁻¹) on the arsenic removal efficiency was investigated. The simulated water sample containing the different concentration of As (III) and other ions was used in the study. The removal of other co-existing ions present in contaminated water was also investigated in column study. The concentration of arsenic was found to be &lt;10 µgL⁻¹ which is below Maximum Contaminant Level (MCL) as per WHO in treated water. The results confirmed that the present system including adsorptive-filtration was successfully used for the treatment of contaminated water containing As (III) ions.