Arsenic removal from naturally contaminated waters: a review of methods combining chemical and biological treatments

The presence of arsenic (As) in aquatic environments is often attributable to geogenic processes occurring within aquifers. Arsenic exists in two prevalent oxidation states, with the trivalent arsenite [As(III)] exerting stronger toxicity effects on the aquatic biota than the pentavalent arsenate [As(V)]. The review evaluates the literature available on the main arsenic removal technologies and the application of combined chemical and biological treatments. We provide a synthetic outlook on the potential strategies of biological As(III) oxidation to As(V) by means of cell-detoxifying mechanisms or metabolic processes with the aim to enhance As removal efficiency. Furthermore, the role of microorganisms in the mobility of arsenic in natural systems as well as the distribution of As-resistant bacteria, potentially suitable for arsenic removal, is discussed in the context of a case study carried out in Latium region (Italy), which is known for arsenic contamination of waters.