This thesis addresses the challenge of real-time Biochemical Oxygen Demand (BOD) measurement in wastewater treatment plants, focusing on the limitations of existing technologies, such as slow response times, large sample requirements, and low operational stability. Microbial fuel cell (MFC) technology was investigated as a viable solution. Although MFCs are self-powered and rely on electroactive biofilms capable of surviving for years, their practical use in real-world biosensing is hindered by challenges such as current instability, reproducibility issues, and high production costs. The main goal of this study was to enhance the operational stability and reliability of MFC-based biosensors while reducing material costs and improving biosensing performance, especially when operated with real urban wastewater (RWW). Four key objectives were pursued:

1. Stability in Real-World Applications: Lab-developed MFC-based biosensors were tested with RWW, demonstrating stability without the need for wastewater pre-treatment. Although recalibration is needed for substrate changes, electroactive biofilms can rapidly adapt without causing significant signal instability.
2. Anode Optimization: The use of a 3D-printed macroporous resin anode was shown to improve biosensor performance, especially in continuous flow systems, significantly enhancing the sensitivity compared to traditional carbon felt (CF) anodes. This was attributed to a lower charge transfer and mass transport resistance, although high flow rates negatively impacted the performance.
3. Cathode Optimization: The study examined the impact of commercial and novel air-cathode materials of MFC-based biosensor performance. The key finding was that the rhodium titanate perovskite catalyst in the air-cathode provided a cost-effective and operationally stable alternative with performance comparable to Pt/C cathodes in the biosensor.
4. Integrated Optimized Anode-Cathode Configurations: Finally, the combination of the optimized 3D-printed anode with rhodium titanate perovskite cathodes proved to be a cost-effective, stable configuration for real-time BOD monitoring. When tested with untreated wastewater, the novel biosensor maintained accuracy and operational stability over extended periods.

Overall, this thesis advances MFC-based biosensor technology, offering a more reliable, cost-effective approach for real-time monitoring of organic pollutants in wastewater treatment plants, paving the way for their practical implementation.