Synergy of Fe and biogenic Mn oxide components mediated by a newly isolated indigenous bacterium to enhance As(III/V) immobilization in groundwater

Biogenic Fe–Mn oxides (BFMO) have shown potential to control As pollution. However, the immobilization of As(III/V) via BFMO generated in situ by indigenous bacteria in groundwater has received little attention. In this study, the oxidation and adsorption of As(III/V) by BFMO induced via a newly isolated indigenous bacterium (Comamonas sp. RM6) and the interaction between the components of BFMO were investigated in high arsenic groundwater by batch experiment combined with structural characterization. The results showed that strain RM6 exhibited high Mn(II) removal capacity (80%) and maximal Mn-oxidizing activity (45%) at the initial Mn(II) concentration of 15 mg/L. The BFMO formed by bacterial induction was a bacteria-mineral complex consisting of Fe oxides (2-line ferrihydrite) and biogenic Mn oxides (δ-MnO2). In the immobilization of BFMO to As(III) and As(V), the As(T) removal efficiencies were 83% and 82%, respectively, in which the Fe oxide component dominated the adsorption of As, while the biogenic Mn oxide component mainly acted as an oxidant. Furthermore, Fe and biogenic Mn oxide components synergistically promoted the immobilization of As(III/V) in groundwater. Therefore, the biostimulation of indigenous Mn oxidizing bacteria and the effective immobilization of As(III/V) via BFMO may be used as a potential strategy for in situ remediation of high arsenic groundwater.