Development and Long-Term Stability of a Novel Microbial Fuel Cell BOD Sensor with MnO₂ Catalyst

Area of Science:

• Environmental Science
• Electrochemistry
• Biosensors

Background:

• Continuous monitoring of biochemical oxygen demand (BOD) is crucial for effective wastewater management.
• Traditional BOD measurement methods are time-consuming and labor-intensive.
• Microbial fuel cells (MFCs) offer a promising platform for developing rapid biosensors.

Purpose of the Study:

• To design and evaluate a novel MFC-based biosensor for continuous BOD monitoring in real wastewater.
• To investigate the efficacy of manganese dioxide (MnO₂) as a cost-effective cathode catalyst.
• To compare the performance of different MnO₂ crystalline structures (β- and γ-MnO₂) in the MFC biosensor.

Main Methods:

• Fabrication of a single-chamber air-cathode MFC biosensor.
• Synthesis and characterization of β- and γ-MnO₂ cathode catalysts.
• Performance evaluation using sodium acetate solutions and real domestic wastewater (DWW).
• Comparison of sensor-predicted BOD values with standard BOD₅ measurements.
• Assessment of long-term operational stability over 1.5 years.

Main Results:

• The MFC biosensor utilizing a β-MnO₂ catalyst achieved optimal performance.
• High correlation coefficients (R² = 0.99 for sodium acetate, R² = 0.98 for DWW) indicated accurate BOD prediction.
• Predicted BOD values for DWW showed good agreement with standard BOD₅ methods (3–12% variation).
• The biosensor demonstrated excellent long-term stability over 1.5 years of continuous operation.

Conclusions:

• Manganese dioxide (MnO₂) is a feasible and cost-effective cathode catalyst for MFC-based BOD biosensors.
• The developed β-MnO₂ MFC biosensor provides accurate and stable online BOD monitoring for real wastewater.
• This research expands the application potential of MFCs for environmental monitoring by utilizing low-cost catalytic materials.