Removal of Cr(VI) from Aqueous Solutions by a Bacterial Biofilm Supported on Zeolite: Optimisation of the Operational Conditions and Scale‐Up of the Bioreactor

The aim of this study was to investigate the feasibility of a bioreactor system and its scale‐up to remove Cr(VI) from solution. The bioreactor is based on an innovative process that combines bioreduction of Cr(VI) to Cr(III) by the bacterium Arthrobacter viscosus and Cr(III) sorption by a specific zeolite. Batch studies were conducted in a laboratory‐scale bioreactor, taking into account different operating conditions. Several variables, such as biomass concentration, pH and zeolite pre‐treatment, were evaluated to increase removal efficiency. The obtained results suggest that the Cr removal efficiency is improved when the initial biomass concentration is approximately 5 g L–1 and the pH in the system is maintained at an acidic level. Under the optimised conditions, approximately 100 % of the Cr(VI) was removed. The scale‐up of the developed biofilm process operating under the optimised conditions was satisfactorily tested in a 150‐L bioreactor.