The aim of this work is to evaluate the applicability of a biofilm to the removal of chromium in solution, at a pilot scale. The effect of the initial concentration of metal on the biosorption behavior of an Arthrobacter viscosus biofilm supported on granular activated carbon, in batch and column essays was also analyzed. Six isotherm equations have been tested in the present study. The best fit was obtained with the Freundlich model. It was observed that as the initial chromium concentration increases, the uptake increases too, but the removal percentage decreases, with values between 95.20% (C-0 = 5 mg/l) and 38.28% (C-0 = 1000 mg/l). The batch adsorption studies were used to develop a pilot bioreactor able to remove chromium from aqueous solutions. Data obtained in a pilot-scale reactor showed an average removal percentage of 99.9%, during the first 30 days, for the initial concentration of 10 mg/l and an average removal percentage of 72%, for the same period and for the initial concentration of 100 mg/l. Uptake values of 11.35 mg/g and 14.55 mg/g were obtained, respectively, for the initial concentration of 10 and 100 mg/l. The results obtained are very promising and encourage the utilization of this biofilm in environmental applications. (C) 2008 Elsevier Ltd. All rights reserved.