Stratified chemical and microbial characteristics between anode and cathode after long-term operation of plant microbial fuel cells for remediation of metal contaminated soils

• Published in: The Science of the total environment Vol. 670; pp. 585 - 594
• Main Authors: Guan, Chung-Yu, Hu, Anyi, Yu, Chang-Ping
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.06.2019
• Subjects: bioelectrochemical process; chromium; electrode; microbial community; Plant microbial fuel cell; soil remediation; bioelectrochemical process; electrode; chromium; microbial community; soil remediation; Plant microbial fuel cell
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.03.096

The plant microbial fuel cell (PMFC) is considered as a sustainable technology in which plants, microbes, and electrochemical cells are the major components and have the synergistic effect on electricity generation. Recent study has demonstrated the use of the PMFC system for remediation of hexavalent chromium (Cr(VI)) contaminated soils; however, the electrokinetic effects, fate of Cr and microbial community shift after long-term operation of PMFCs still need to be unveiled. In this study, PMFCs with spiking 50 mg/kg Cr(VI) were operated over 10 months and chemical and microbial characteristics of different locations of PMFC systems were investigated. Distinct chemical and microbial properties for different locations of soil samples were observed within PMFCs. For instance, the pH values of soils around the cathode and anode (cathode and anode soils) in PMFCs with Chinese pennisetum (Chinese pennisetum PMFCs) were 7.03 ± 0.15 and 6.09 ± 0.05 respectively, showing significantly higher pH values of cathode soils than those of anode soils. The electrical conductivity (EC) of cathode and anode soils in Chinese pennisetum PMFCs was 78.00 ± 5.61 and 156.25 ± 7.89 μs/cm respectively, showing significantly lower ECs of cathode soils than those of anode soils. The total Cr of cathode and anode soils in Chinese pennisetum PMFCs was 65.75 ± 3.77 and 84.29 ± 2.87 mg/kg respectively, showing significantly lower total Cr of cathode soils than that of anode soils. The permutational multivariate analysis of variance test of results of 16S rRNA gene high-throughput sequencing revealed that microbial communities in anode and cathode samples had significant difference in compositions. The stratified chemical and microbial characteristics between anode and cathode were primarily driven by the bioelectrochemical processes and electrokinetic effects within PMFCs. The findings in this study help to better understand the underlying effects of operating PMFCs and will be beneficial for future application of PMFCs in the remediation of heavy metal-contaminated soils. [Display omitted] •Stratified chemical and microbial characteristics between anode and cathode in PMFCs•Long-term operation of PMFCs caused significantly higher pH in cathode soils.•PMFCs caused significantly lower ECs in cathode soils than in anode soils.•Significantly lower total Cr of cathode soils than that of anode soils was observed.•Microbial communities were significantly different between anode and cathode.