Hexavalent chromium removal from a tannery effluent by a bacterial consortium

The objective of this work concerns to exploit the power of bacteria for hexavalent chromium removal the tannery effluents. To reach this purpose, fifty bacterial isolates were isolated from abandoned lead mines soil in Morocco. Resistance of these bacteria to certain heavy metals (Cr(VI), Pb, Cd, Hg, Co, Ni, Cu, Zn and Mn) was tested in vitro under various concentrations (5 - 3500 mg/L). Four bacterial isolates have shown hexavalent chromium resistance up to 800 mg/L. In addition, we have observed a multi-metal resistant and no antagonistic activity between them. DNA sequencing of the 16S ribosomal RNA gene have allowed identifying these four bacteria: Bacillus subtilis, Kocuria rosea, Staphylococcus lentus and Bacillus subtilis subsp. spizizenii. These four bacteria multi-metal resistant were used at consortium for hexavalent chromium removal of tannery effluent. This elimination, is evaluated by reaction with 1,5-diphenylcarbazide (DPC). After five days of incubation at 30°C, the results show that rate of removal are 76%, 25%, 12.5% and 3.34% for the concentrations 50 mg/L, 100 mg/L, 200 mg/L and 300 mg/L respectively in the effluent.