Cr(VI) reduction in chromium-contaminated soil by indigenous microorganisms under aerobic condition

Bioremediation plays an increasingly important role in the remediation of chromium-contaminated soil because it is an environmentally friendly technology. To investigate the Cr(VI) reduction process by indigenous microorganisms in soil, a batch of incubation experiments were carried out in a bioreactor under aerobic conditions. The results showed that in the presence of indigenous microorganisms, the Cr(VI) concentration in the chromium-contaminated soil decreased from 1521.9 to 199.2 mg/kg within 66 h with culture medium addition, while a slight decrease in the Cr(VI) concentration was found in the sterilized soil, implying that the indigenous microorganisms contributed to the Cr(VI) reduction. In the microbial remediation process, Cr(VI) microbial reduction occurred after the reduction of NO3-, Mn4+ and Fe3+ and, before SO42- reduction. The reduction process of Cr(VI) can be divided into two phases, characterized by the exponential equation model of microbial reduction and the linear equation model of the combined effect of the major ions. It can be concluded that indigenous Cr(VI)-reducing bacteria have a potential application for in-situ remediation of Cr(VI)-contaminated soil.