Bacterial Diversity in Biological Filtration System for the Simultaneous Removal of Arsenic, Iron and Manganese from Groundwater

Bacterial diversity of the microbial consortia in a biological filtration pilot plant for the simultaneous removal of arsenic (As), iron (Fe) and manganese (Mn) from groundwater was analyzed. PCR-based denaturing gradient gel electrophoresis (DGGE) of bacterial 16S ribosomal RNA (rRNA) genes represented at least 6 dominant signals and many weak signals. Phylogenetic analysis using the nucleotide sequences of the 16S rRNA gene clone library constructed from the pilot plant sample showed the presence of the bacteria closely related to Gallionella and Leptothrix, which are supposed to be involved in the production of Fe and Mn oxides utilized for adsorbents of As in this system. On the other hand, aoxB gene was not detected, suggesting that arsenite-oxidizing bacterium would not be involved in the As removal of the pilot plant. These results indicated that the simultaneous removal of As, Fe and Mn from groundwater was conducted by the physicochemical sorption of As by the biogenic Fe and Mn oxides produced by the bacteria closely related to Gallionella and Leptothrix included in the microbial consortia of the pilot plant.