Characterization of biospheric bacterial community on reduction and removal of chromium from tannery contaminated soil using an integrated approach of bio-enhanced electrokinetic remediation

Intensive research efforts on different methods focus on reducing toxic Cr(VI) to less toxic Cr(III). However, most methods end up in improper removal, recurrence or subsequent pollutant generation. Therefore, our study focuses on the reduction and removal of Cr with no recurrence possibilities. So, the indigenous biospheric bacterial community is characterized by Metagenomics using EPI2ME 16S workflow Bioinformatics tool. The obtained metagenome raw data has been submitted in NCBI database with reference to the Bio Project ID PRJNA679434. Based on this data, the possible bio-mechanisms behind the reduction of Cr(VI) to Cr(III) by FeS particles generated by the biospheric microbes (4.5 x 10(3)) was elucidated. Electrokinetic (EK) experiments further removed the reduced Cr(III) by Bio-enhanced electrokinetic remediation (BEER) approach. The presence of Mn (3.54%) in the soil was found to oxidize the reduced Cr(III) to Cr(IV), thus ruling out the Cr(VI) recurrence. The integrated approach of BEER showed an effective removal of Cr and Fe in the contaminated soil. Physicochemical parameters such as chemical oxygen demand (COD) was assessed and found to show a drastic removal efficiency of 70% after the EK treatment. Thus, the presence of sulphide content (122 mg/L) generated by the biospheric microbial community was found to enhance the Cr(VI) reduction and Cr(III) removal significantly, thus proving the effectiveness of the BEER approach to overcome the drawback of Cr recurrence in heavy metal contaminated soil environments.

Automated summary

Intensive research efforts have focused on reducing toxic Cr(VI) to less toxic Cr(III), but many methods end up with improper removal or recurrence. This study characterized the biospheric bacterial community using Metagenomics and elucidated the bio-mechanisms behind the reduction of Cr(VI) to Cr(III) by FeS particles. The BEER approach effectively removed Cr and Fe in contaminated soil, with sulphide content enhancing Cr reduction and removal.