Background: Cr (VI) is a highly toxic and carcinogenic contaminant and that are used in the steel industry and other chemical industries such as the leather industry, pigment production, electroplating of metals and the production of anticorrosive compounds. Its waste enters the environment and subsequently enters the water and food sources. Therefore, in order to protect the environment as well as human health, it is necessary to remove this pollutant from the environment, including soil, using appropriate methods.
Material and Methods: Chromium resistant bacteria were isolated from the chromium contaminated soil and adapted by serial culture in Cr (VI) concentrations of 50-400 mg/L and microorganism growth and Cr (VI) reduction were measured. Then the soil was artificially contaminated at the laboratory by Cr (VI) compound (CrO₃) and Organic compounds were added to soil at the Specified amount. Finally, a separated bacterial mix was added to the soil to initiate the bioaugmentation process.
Results: After 3 stages of sampling and data analysis, the results of the study showed that Cr (VI) reduction efficiency by the bacterial mix reduced decrease by Cr (VI) concentration increase. So, under similar conditions, the efficiency of Cr (VI) reduction of soil, at a concentration of 50 , 200 and 350 mg / l, is about 86%, 51% ,and 26% respectively .Organic compound adding also increase bioaugmentation efficiency.
Conclusion: The results of this study showed that optimizing soil conditions could improve the biodegradation process, especially in low concentrations of contaminants.