Arsenic oxidation capabilities of a chemoautotrophic bacterial population: Use for the treatment of an arsenic contaminated wastewater

Abstract

An autotrophic bacterial population, named CAsOl, able to oxidise arsenic has been isolated from a former gold mine (Saint-Yrieix, France). This bacterial population was composed of two microorganisms: a bacterial strain close to Ralstonia picketii and the second one related to Thiomonas genus (identification by 16S rDNA sequencing). This microbial consortium was able to oxidise arsenic with CO ₂ as the carbon source, arsenite as electron donor and oxygen as electron accepter. A significant oxidising activity was observed in a pH range comprised between 3 to 8 (pH optimum 5-7). A laboratory experiment for the biological treatment of a synthetic effluent containing 100 mg.L ^-1 of arsenic has been carried out. A mineral support, pouzzolana, has been colonised by the population CAsOl and the column was fed continuously with a synthetic medium in order to determine the maximal arsenic oxidation rate and the optimal residence time. In our experimental conditions, the maximum arsenic oxidation rate was 3,9 g As(Ill). L ^-1.day ^-1 with a residence time of 1 hour after 55 days of continuous running. The performance of our bacterial population for arsenite oxidation in arsenic contaminated wastewater are especially important in the case of a treatment of arsenious wastewater as it presents advantages compared to physico-chemical treatments (consumption and cost of chemicals, potential toxic by-products generation...).