Ex situ bioremediation of Cr(VI) contaminated soil by Bacillus sp.: Batch and continuous studies

This study presents the ex situ batch and continuous bioremediation of tannery effluent contaminated soil using Bacillus sp. isolated from hexavalent chromium (Cr(VI)) contaminated environment. The remediation of Cr(VI) contaminated soil by conventional methods is challenging and hence, the present study aims to address this issue by examining ex situ bioremediation of Cr(VI) contaminated soil. The elemental composition of the soil was analyzed by SEM–EDX. The leachate of the soil was remediated using Bacillus sp. and the effect of temperature, pH and inoculum volume on the process performance was explored. The influence of electron donors such as glucose, fructose, sucrose and bagasse extract on Cr(VI) reduction was also enumerated. The optimum pH and temperature were found to be 7 and 37 °C respectively and glucose was found to offer higher Cr(VI) reduction compared to other electron donors. The reduction was found to follow Arrhenius equation and the enzyme responsible for the reduction was found to be chromium reductase. The continuous reduction of Cr(VI) was carried out in a packed bed reactor using sand as the inert support for Bacillus sp. The analysis of kinetics and mass transfer aspects of the process was done with simple models.