ABSTRACT
Hexavalent chromium contamination is caused by different industrial applications and commercial processes, which eventually lead to environmental pollution (soil, surface water, or atmosphere), resulting in serious human health diseases. Biological chromium-removal methods are a sustainable alternative technology of lower impact on the environment. Different detoxifying mechanisms developed by microorganisms (e.g. bacteria, fungi, and yeasts) include the metal uptake, which can either occur actively (bioaccumulation) or passively (biosorption), and/or the biotransformation (reduction or oxidation), changing the oxidative state of the metals. This chapter summarizes hexavalent chromium-bioremediation technologies oriented toward practical applications of larger scale technologies. In the same way, a comparative study of different systems (reactors) and the establishment of the optimum conditions of operation (hydrodynamic, mass transfer, and growth conditions) for the removal of heavy metals are presented. Also, the most relevant results of several investigations focused on the evaluation of the process feasibility and the robustness of the pilot scale system trials in chromium-removal capacity are highlighted.
