Domestic wastewater treatment using multi-electrode continuous flow MFCs with a separator electrode assembly design

Area of Science:

• Environmental Engineering
• Electrochemistry
• Biotechnology

Background:

• Microbial fuel cells (MFCs) offer a promising method for domestic wastewater treatment.
• Scaling MFCs for continuous flow presents challenges due to fluctuating chemical oxygen demand (COD) levels.
• Multiple electrodes in MFCs are necessary for efficient treatment but complicate continuous operation.

Purpose of the Study:

• To investigate the performance of a multi-anode MFC under continuous flow domestic wastewater treatment.
• To evaluate strategies for enhancing current generation in MFCs under varying COD conditions.
• To optimize MFC design for efficient and stable wastewater treatment.

Main Methods:

• A single-chamber MFC with multiple graphite fiber brush anodes and a single air cathode was utilized.
• Fed-batch and continuous flow operations were compared, with varying hydraulic retention times (HRTs).
• Anode wiring configurations and series reactor arrangements were tested to improve performance.

Main Results:

• Fed-batch operation achieved high COD removal (>90%) and power density (120 mW/m²).
• Continuous flow operation with a single reactor showed significantly reduced current density (20 mA/m²) due to a 57% COD change.
• Separately wiring anodes increased current density to 55 mA/m², while connecting two MFCs in series further improved it to 73 mA/m².

Conclusions:

• Continuous flow wastewater treatment in multi-anode MFCs is limited by COD concentration changes.
• Configuring multiple MFCs in series is an effective strategy to enhance current generation and wastewater treatment efficiency.
• Minimizing COD fluctuations across anodes in series reactors is key to improving MFC performance in continuous flow systems.