Pilot scale microbial fuel cells using air cathodes for producing electricity while treating wastewater.

Area of Science:

• Environmental Engineering
• Electrochemistry
• Wastewater Treatment

Background:

• Microbial fuel cells (MFCs) offer a promising route for simultaneous wastewater treatment and energy generation from organic matter.
• Previous pilot-scale MFC studies were limited by energy recovery issues associated with aerated catholytes.
• Demonstrating large-scale MFCs that treat real wastewater efficiently is crucial for technological advancement.

Purpose of the Study:

• To develop, deploy, and test a large-scale air-cathode MFC for treating domestic-type wastewater.
• To evaluate the electrochemical and wastewater treatment performance of the system over an extended period.
• To assess the energy recovery potential and pollutant removal efficiency of the MFC technology.

Main Methods:

• A 850 L air-cathode MFC (1400 L total liquid volume) was constructed and operated at a wastewater treatment facility.
• The MFC featured 17 brush anode modules and 16 cathode modules with passive air flow for the air cathodes.
• Wastewater was processed over a 12-hour hydraulic retention time (HRT), followed by treatment in a biofilter (BF).

Main Results:

• The MFC generated an average power of 0.46 ± 0.35 W (0.043 W m^-2) with a coulombic efficiency of 9%.
• The MFC alone removed 49% of COD, 70% of BOD₅, and 48% of TSS.
• The combined MFC/BF system achieved up to 91% COD and 91% BOD₅ removal, along with significant reductions in E. coli (98.9%) and fecal coliforms (99.1%).

Conclusions:

• The tested air-cathode MFC represents the largest scale deployment to date, proving its capability in treating real wastewater.
• The system demonstrates substantial pollutant removal and pathogen reduction, highlighting its potential for sustainable wastewater management.
• This study provides a viable path forward for the large-scale application of MFC technology in wastewater treatment.