Remediation of PAH polluted soils using a soil microbial fuel cell: Influence of electrode interval and role of microbial community

The soil microbial fuel cells (SMFCs) were constructed to remediate soils contaminated by polycyclic aromatic hydrocarbons (PAHs). With a maximum power density of 12.1 mW m−2 and an internal resistance of 470 Ω, a closed SMFC showed electricity generation comparable to that by an open SMFC after 175 days of operation and meanwhile increased the removal rates of anthracene, phenanthrene, and pyrene to 54.2 ± 2.7%, 42.6 ± 1.9% and 27.0 ± 2.1% from 20.8 ± 1.1%, 17.3 ± 1.2% and 11.7 ± 0.9%, respectively, by the open SMFC. Both the electricity generation and the removal of PAHs increased with the decreased electrode interval. When the electrode interval ranged between 4 cm and 10 cm, the more closely the electrodes were positioned, the more efficient the electricity generation and removal of PAHs became. Dominated by the genus of Geobacter, the SMFC was enriched in electrogenic bacteria at the anode surface, and the growth of certain microbes other than electrogenic bacteria in the soil was improved by electrical stimulation. This finding reveals the critical mechanism underlying electricity generation and improved the removal of PAHs.