Biological As(III) Oxidation Coupled with As(V) Interception by Fibrous Anion Exchange Material FFA-1

Abstract

A combined process, including As(III) oxidation and As removal by the fibrous anion exchange material FFA-1, was established to treat arsenite ([As(III)] = 10 mg L−1)-polluted groundwater. Both fixed-bed reactors (R1 and R2) were separately filled with pozzolana and FFA-1. After 72 h of inoculation and 10 days of operation, As(III) oxidation efficiency reached around 100% and the total As in the effluent was below 10 µg L−1 for over 100 days. Then, the combined system was stopped and a desorption experiment on the FFA-1 collected from R2 was carried out. The results revealed that the As trapped by the FFA-1 was distributed linearly along the axial length of R2, and the maximum capacity for removal of the FFA-1 from R2 was about 28 mg As g−1 FFA-1. Moreover, the anions’ competing test showed that they were preferentially sequestrated by the FFA-1 according to the following order: SO42− > PO43− ≈ AsO43− > NO3− at neutral pH. Furthermore, the microorganisms attached to the FFA-1, including some arsenite-oxidizing microorganisms (AsOBs), could be a beneficial complement to the As(III) oxidation and, thus, the total As removal. At the same time, the regeneration test proved that the As(V) interception capacity of FFA-1 was barely affected by the presence of biofilm. Additionally, the calculated operating cost showed that this combined process has great potential for the remediation of As-polluted groundwater.