The objective of this work is the definition of an efficient biosorption system based on the ability of some
microorganisms, metabolica1ly active or not, to retain heavy metals, specially the hexavalent fonn of Cr.
Metallic solutions were passed through mini-colunms in which a biotilm was developed at pre-established
conditions. As industrial wastewater usually contains organic and inorganic compounds, besides metallic ions,
it would be desirable to co-extract several pollutants at the same time. The utilization of granular activated
carbon (GAC) as a support for the biofilm seems to be advantageous, as it can retain other substances while
the biofilm removes the heavy metal. To quantify the contribution of GAC to the overall removal of
chromium, adsorption studies were carried out with the determination the effect of pH and of the presence of
concurrent species on the adsorption isotherms. Biosorption studies were done with three different bacteria,
Pseudomonasjluorescens, Escherichia coli and Arthrobacter viscosus. Among microorganisms, bacteria are
particularly interesting for the purpose as they are able to excrete polysaccharides allowing a good adhesion
to the support, implementing the retention capacity of the biosystem and protecting the cells from the
xenobiotic effect of the heavy metal ions. Removal efficiencies were compared between the three biosystems
