Evaluation of Fe(III) Reducing Microorganisms for the Biostabilisation of Chromium in Contaminated Soils

摘要

Hexavalent chromium (Cr(VI)) is a common and highly toxic-contaminant in soils. Most remediation strategies developed for Cr(VI) contaminated soils aim at reducing the hexavalent form to the less toxic trivalent state, Cr(III), which can be efficiently immobilised in situ due to the very low solubility of Cr(III) compounds. This conversion can be achieved by conventional chemical methods. Another alternative is the exploitation of microbial processes, using microorganisms that exhibit the appropriate metal bioreduction potential. Current study investigates the possibility of exploiting the metabolic activity of an iron reducing microorganism, Desulfuromonas palmitatis. During the initial experiments Cr(VI) was added in the growth medium of the microorganism at three levels, i.e. 5, 15 and 30 mg/l. Complete reduction was obtained at all three concentrations, but growth of the bacteria was observed only in the medium with the lowest initial Cr(VI) content, i.e. 5 mg/l. In the subsequent experiments D. palmitatis were used for the treatment of soil samples artificially contaminated with Cr(VI) at two levels, i.e. 200 and 500 mg/kg. Experimental results with soils confirmed the bioreducing potential of D. palmitatis.