There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Microbial fuel cells: From fundamentals to applications. A review

Research into alternative renewable energy generation is a priority, due to the ever-increasing concern of climate change. Microbial fuel cells (MFCs) are one potential avenue to be explored, as a partial solution towards combating the over-reliance on fossil fuel based electricity. Limitations have slowed the advancement of MFC development, including low power generation, expensive electrode materials and the inability to scale up MFCs to industrially relevant capacities. However, utilisation of new advanced electrode-materials (i.e. 2D nanomaterials), has promise to advance the field of electromicrobiology. New electrode materials coupled with a more thorough understanding of the mechanisms in which electrogenic bacteria partake in electron transfer could dramatically increase power outputs, potentially reaching the upper extremities of theoretical limits. Continued research into both the electrochemistry and microbiology is of paramount importance in order to achieve industrial-scale development of MFCs. This review gives an overview of the current field and knowledge in regards to MFCs and discusses the known mechanisms underpinning MFC technology, which allows bacteria to facilitate in electron transfer processes. This review focusses specifically on enhancing the performance of MFCs, with the key intrinsic factor currently limiting power output from MFCs being the rate of electron transfer to/from the anode; the use of advanced carbon-based materials as electrode surfaces is discussed.

/pdf/microbial-fuel-cells-an-overview-of-current-technology-25y9lplmsd.pdf

Microbial fuel cells: An overview of current technology

Different microbial electrochemical technologies are being developed for many diverse applications, including wastewater treatment, biofuel production, water desalination, remote power sources, and biosensors. Current and energy densities will always be limited relative to batteries and chemical fuel cells, but these technologies have other advantages based on the self-sustaining nature of the microorganisms that can donate or accept electrons from an electrode, the range of fuels that can be used, and versatility in the chemicals that can be produced. The high cost of membranes will likely limit applications of microbial electrochemical technologies that might require a membrane. For microbial fuel cells, which do not need a membrane, questions about whether larger-scale systems can produce power densities similar to those obtained in laboratory-scale systems remain. It is shown here that configuration and fuel (pure chemicals in laboratory media vs actual wastewaters) remain the key factors in power pro...

http://pubs.acs.org/doi/pdf/10.1021/acs.estlett.5b00180

Assessment of Microbial Fuel Cell Configurations and Power Densities

Wastewater treatment in microbial fuel cells – an overview

A 90-liter stackable baffled microbial fuel cell for brewery wastewater treatment based on energy self-sufficient mode

A combined microbial desalination cell and electrodialysis system for copper-containing wastewater treatment and high-salinity-water desalination.

Field tests of cubic-meter scale microbial electrochemical system in a municipal wastewater treatment plant

Energy self-sufficiency is a highly desirable goal of sustainable wastewater treatment. Herein, a combined system of a microbial fuel cell and an intermittently aerated biological filter (MFC-IABF) was designed and operated in an energy self-sufficient manner. The system was fed with synthetic wastewater (COD = 1000 mg L−1) in continuous mode for more than 3 months at room temperature (~25 °C). Voltage output was increased to 5 ± 0.4 V using a capacitor-based circuit. The MFC produced electricity to power the pumping and aeration systems in IABF, concomitantly removing COD. The IABF operating under an intermittent aeration mode (aeration rate 1000 ± 80 mL h−1) removed the residual nutrients and improved the water quality at HRT = 7.2 h. This two-stage combined system obtained 93.9% SCOD removal and 91.7% TCOD removal (effluent SCOD = 61 mg L−1, TCOD = 82.8 mg L−1). Energy analysis indicated that the MFC unit produced sufficient energy (0.27 kWh m−3) to support the pumping system (0.014 kWh m−3) and aeration system (0.22 kWh m−3). These results demonstrated that the combined MFC-IABF system could be operated in an energy self-sufficient manner, resulting to high-quality effluent.

/pdf/a-combined-system-of-microbial-fuel-cell-and-intermittently-rth73uwdz7.pdf

A combined system of microbial fuel cell and intermittently aerated biological filter for energy self-sufficient wastewater treatment.

Certain mixed consortia colonized on aerobic biocathodes can improve the 4-electron oxygen reduction of cathodes; however, the coupling interaction of the cathodic reaction and microbial metabolism remains unclear. To better understand the abovementioned interaction evolved in the cathodic process, biocathodes were enriched using nitrifying sludge and operated at various NH4Cl and NaHCO3 concentrations in both the open and closed external circuit conditions. Based on the variation of the nitrification and cathodic oxygen reduction activities, it was shown that the oxygen reduction process, to some extent, relied on the nitrification activity of the biocathode; the external electrons from the cathode, in turn, might benefit the nitrifying bacteria selected in the MFC habitat by entering the electron transfer chains as the energy source. Nitrifiers, including Nitrosomonas sp., Nitrospira sp. and Nitrobacter sp., were detected in all the biocathodes that were cultured in different conditions, even the ones cultured without NH4Cl in the medium. These findings provided valuable insights into the possible working mechanism of biocathodes.

Yue Dong

Papers

A 90-liter stackable baffled microbial fuel cell for brewery wastewater treatment based on energy self-sufficient mode

A combined microbial desalination cell and electrodialysis system for copper-containing wastewater treatment and high-salinity-water desalination.

Field tests of cubic-meter scale microbial electrochemical system in a municipal wastewater treatment plant

A combined system of microbial fuel cell and intermittently aerated biological filter for energy self-sufficient wastewater treatment.

Coupling interaction of cathodic reduction and microbial metabolism in aerobic biocathode of microbial fuel cell