Simultaneous nitrification and denitrification with electricity generation in dual-cathode microbial fuel cells

Background: Nitrogen removal using microbial fuel cells (MFCs) is of great interest owing to the potential benefits of bioenergy production. In this study, simultaneous nitrification and denitrification in dual-cathode MFCs was investigated. Results: The dual-cathode MFCs investigated were capable of generating electricity and removing nitrogen, influenced by operating methods, nitrogen loading rates and external resistance. Depending on the ammonium concentration in the anode chamber, 84-97% of the ammonium nitrogen was removed via nitrification in the aerobic cathode. The removals of nitrate and total nitrogen were relatively low (~50%) at the influent ammonium concentration of 80 mg NH ₄ ⁺-N L ^-1, but were significantly improved to more than 90% at a lower ammonium input (40 and 20 mg NH ₄ ⁺-N L ^-1). When the electrode couples were electrically connected for different purposes, with high power output from the anode/aerobic cathode and high current generation from the anode/anoxic cathode, nitrogen removal was also improved. An investigation of aeration suggested that factors other than carbon supply, possibly inefficient reactor configuration, also limited the performance of the developed MFC. Conclusion: The experimental results demonstrated that the proposed pathway was feasible with effective nitrogen and organic removal. This study provided valuable information for the further development of a continuously operated dual-cathode MFC system.