Electricity generation from artificial wastewater using an upflow microbial fuel cell

Area of Science:

• Environmental Science
• Electrochemistry
• Biotechnology

Background:

• Upflow microbial fuel cells (UMFCs) offer a dual function of electricity generation and wastewater treatment.
• Optimizing UMFC performance requires understanding factors affecting power output and efficiency.

Purpose of the Study:

• To investigate the electricity generation potential of UMFCs fed with sucrose.
• To identify limiting factors for power density in UMFCs.
• To assess the impact of chemical oxygen demand (COD) loading rates on UMFC performance.

Main Methods:

• Continuous operation of an UMFC for five months with sucrose as the electron donor.
• Addition of hexacyanoferrate as an artificial electron mediator.
• Varying COD loading rates and measuring power density.
• Analysis of internal resistance and Coulombic efficiency.
• Cyclic voltammetry (CV) to assess substrate diffusion limitations.

Main Results:

• Maximum power density of 170 mW/m² achieved with hexacyanoferrate.
• Power density increased with COD loading up to 2.0 g COD/L/day, then plateaued.
• Internal resistance (84 Ω) was a major limiting factor for power output.
• Low Coulombic efficiencies (0.7–8.1%) indicated inefficient organic matter conversion to electricity.
• Over 90% soluble COD (SCOD) removal efficiency was maintained, primarily due to methanogenic activity.
• CV indicated substrate transport limitations.

Conclusions:

• UMFCs can generate electricity while treating wastewater, but performance is constrained by internal resistance and substrate diffusion.
• Hexacyanoferrate enhances power density, but optimization is needed to overcome limiting factors.
• Methanogenesis plays a significant role in SCOD removal, impacting Coulombic efficiency.