Increasing removal of benzene from groundwater using stacked tubular air-cathode microbial fuel cells

This work develops a small-scale microbial fuel cell (MFC) and evaluates their performance in series or in parallel as a tubular MFC (t-MFC) in removing benzene from groundwater and generating electricity. The results indicate that the time required (t_r) for t-MFC to remove all benzene was half of that required by a single MFC. The maximum power density (P_max) of the serially-connected t-MFC was 12.7 mW/m², a 3.3-fold increase over the single t-MFC. An optimal benzene removal efficiency with a t_r of four days was achieved under persistent aeration at the cathode of the t-MFC, and this t_r was 1.25–3-fold lower than those obtained under other aeration conditions. Tubular MFCs connected in series had a higher open-circuited voltage (655 mV) and a lower t_r, but the P_max and maximum current density of the parallelly-connected t-MFC were 3.8 and 1.5 times those of the t-MFC with a serial connection. Intermittent aerating of the cathode improved the removal of benzene and the generation of electricity in a t-MFC by providing sufficient levels of oxygen for the reaction to achieve P_max. The small t-MFC was easily scaled up by stacking MFCs in series mode, with great potential for field-scale application for in situ bioremediation in hydrocarbon-contaminated groundwater.