Microbially assisted arsenic removal using Acidothiobacillus ferrooxidans mediated by iron oxidation

The aim of this investigation was to determine the efficiency of arsenic removal present in acidic water using the biochemical method in presence of Acidothiobacillus ferrooxidans bacteria and ferrous ions. The process includes the bio-oxidation of ferrous to ferric by bacteria with simultaneous conversion of arsenite to arsenate and its removal by chemical method. The experiments were carried out in shake flasks with or without A.ferrooxidans culture. The variables of the pH, temperature, cell density and initial concentration of ferrous ions in the growth medium of A.ferrooxidans bacteria were examined in the laboratory to determine how they affect the removal of arsenic. It was found that the maximum arsenic removal (80%-85%) occurred at ferrous ions concentration of 2 gL−1 at the temperature of 35 °C with the initial cell density of 3.66 × 107 cells/mL and initial pH value of 2.5 with 70%-75% bio-oxidation of ferrous ions. The results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses have confirmed the growth of bacteria and identify the nature of precipitate generated by the bacteria. The finding showed that arsenic can be removed considerably in this process in an efficient and greener way, but also removing efficiency was much more (<80%) in acidic wastewater. The ANOVA and LSD statistical analysis were performed to assess any significant differences occurred among the four different levels of each variable. This study verified that combination of bio-oxidation with filtration improves the removal efficiency of arsenic.