Chapter 4 - Arsenic removing prokaryotes as potential biofilters

Abstract

Biofiltration is a significant process where microorganisms with selective capacity remove pollutants and are immobilized on the bedding material in order to treat the fluid of interest. Biofilters have great potential to treat contaminated water. Arsenic (As) contamination of water has become a major concern in various parts of the world. Local hydrology, geology and geochemical characteristics of the aquifer determine the As level in the ground water. Commonly, oxidation of arsenopyrite releases As, which can exist in four oxidation states (As5+, As3+, As0, and As3−). Prolonged exposure to even low As concentration may result in severe health hazards that include arsenicosis and cancer due to DNA damage. In recent decade, numerous phylogenetically diverse prokaryotes have been explored for transforming As(V) and As(III) in a variety of terrestrial and aquatic habitats and at a wide range of environmental conditions. Some heterotrophic bacteria can oxidize As(III) leading to detoxification, while others may use As(III) as an electron donor. Bacteria have developed mechanism of chemoautotrophic As(III) oxidation via aerobic oxidation, anaerobic nitrate- and selenate-dependent respiration or phototrophy. Thus, biofilters with immobilized As removing/detoxifying microorganisms can be most promising water treatment strategy for bioremediation of As contaminated ground water. In this chapter, an elaborate account of As related toxicity and conventional methods for As removal is presented. Further, comprehensive information about the vast amount of literature available on the various groups of prokaryotic microbial diversity with As metabolizing potential has been presented here. Finally, the potential of this microbial diversity for developing effective biofiltration strategies with their advantages and disadvantages are discussed.