Microbial oxidation of arsenic : the potential for exploitation in drinking water treatment
Arsenic (As) contamination of drinking water is a problem prevalent throughout the world, and it has become more pertinent in the US following a recent reduction in the maximum contaminant limit (MCL) to 10 μg/L. Because As(V) is typically easier to remove than is As(III), arsenic is often chemically oxidized using free chlorine or permanganate. However, exploiting microorganisms to oxidize arsenic might have potential. In this study, microorganisms were isolated from water and filter media collected from the full-scale Greene County, Ohio drinking water treatment plant and from bench-scale filters seeded with filter media from the Greene County plant. These isolates were screened for arsenic-oxidation capability and resistance to arsenic. Molecular techniques, including 16S ribosomal RNA gene sequencing and terminal restriction fragment length polymorphism (T-RFLP) analysis, were used to phylogenetically identify and fingerprint the isolates, respectively. In addition, a gene probe targeting a region of the arsenite oxidase enzyme was used to demonstrate the presence of arsenic-oxidizing bacteria in the full-scale and bench-scale samples. Microbial arsenic-oxidizers could be an attractive alternative to the chemical oxidants that are traditionally used in arsenic treatment.