Microbial electrochemical Cr(VI) reduction in a soil continuous flow system

Area of Science:

• Environmental Science
• Environmental Engineering
• Microbiology

Background:

• Contaminated soil and groundwater pose significant environmental risks.
• Microbial electrochemical technologies (METs) integrate biological and electrochemical methods for contaminant remediation.
• Hexavalent chromium (Cr(VI)) is a toxic contaminant requiring effective removal strategies.

Purpose of the Study:

• To investigate Cr(VI) reduction using a bioelectrochemical continuous flow (BECF) system with soil-buried electrodes.
• To simulate in situ microbial electrochemical treatment for groundwater plumes.
• To compare the efficiency of the BECF system against abiotic and open-circuit controls.

Main Methods:

• A bioelectrochemical continuous flow (BECF) system with soil-buried electrodes was employed.
• Tests were conducted using chromium-contaminated solutions (20–50 mg Cr(VI)/L).
• Bacterial communities in soil and planktonic samples were characterized using sequencing.

Main Results:

• The BECF system achieved a Cr(VI) removal rate of 1.00 mg/(L·day) at 20 mg/L initial concentration, reaching 99.5% removal in nine days.
• At 50 mg/L initial concentration, the BECF system achieved 99.9% Cr(VI) removal over 156 days, significantly outperforming the open-circuit control.
• Distinct bacterial communities were identified in soil and planktonic samples, suggesting diverse microbial roles in Cr(VI) reduction.

Conclusions:

• Microbial electrochemical removal of hexavalent chromium is highly efficient, especially in the absence of organic carbon.
• The BECF system demonstrates a sustainable and innovative approach for soil and groundwater remediation.
• The complexity of microbial communities indicates multifaceted biological processes contributing to chromium removal.