Improving the configuration and architecture of a small-scale air-cathode single chamber microbial fuel cell (MFC) for biosensing organic matter in wastewater samples

Power production in microbial fuel cells has been proposed as a novel method to sense organic matter concentration in water resources. The development of microbial fuel cells as biosensors is relatively new, and still facing major issues such as response time and operation ranges. The present work aims at improving the configuration and architecture of a small-scale, air-cathode single chamber microbial fuel cell (MFC) to biosense organic matter in wastewater samples. Different MFC models were tested using CFD. The number of channels and flow disturbances was increased to minimize dead zones, increasing the Reynolds number (or shear rate), and with special emphasis on the interface between the electrodes and the substrate seeking the greatest contact. The best model obtained was built and tested with synthetic wastewater. The final Single Chamber Microbial Fuel Cell (SCMFC) version consisted of a 2 cm³ total volume as the anodic chamber. Carbon cloth was used as electrodes (4 cm² of exposed surface area), and two different cell configurations were evaluated, a membrane cell (MFC-m) and a membrane-less cell (MFC-ml). The MFCs were tested in a Chemical Oxygen Demand (COD) range varying from 25 to 200 mg L⁻¹. Coulombic Efficiency (CE %), sensibility, and response time were determined as comparative sensing parameters. The MFC-ml resulted in a lower CE percentage (8% vs 13 % for the MFC-m), a lower response time (45 ± 6.4 min vs 63 ± 10 min for the MFC-m), and a lower quantification difference compared to the COD traditional quantification method. Flow velocity simulation was a useful tool to improve MFC design. The MFC-ml could reduce construction costs, and enable simplification of the operation of the MFC-based sensing device, which contributes to its implementation in real water quality monitoring scenarios.