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The traditional microbial fuel cell (MFC) sensor with bioanode as sensing element delivers limited sensitivity to toxicity monitoring, restricted application to only anaerobic and organic rich water body, and increased potential fault warning to the combined shock of organic matter/toxicity. In this study, the biocathode for oxygen reduction reaction was employed for the first time as the sensing element in MFC sensor for toxicity monitoring. The results shown that the sensitivity of MFC sensor with biocathode sensing element (7.4±2.0 to 67.5±4.0 mA% −1 cm −2 ) was much greater than that showed by bioanode sensing element (3.4±1.5 to 5.5±0.7 mA% −1 cm −2 ). The biocathode sensing element achieved the lowest detection limit reported to date using MFC sensor for formaldehyde detection (0.0005%), while the bioanode was more applicable for higher concentration (>0.0025%). There was a quicker response of biocathode sensing element with the increase of conductivity and dissolved oxygen (DO). The biocathode sensing element made the MFC sensor directly applied to clean water body monitoring, e.g., drinking water and reclaimed water, without the amending of background organic matter, and it also decreased the warning failure when challenged by a combined shock of organic matter/toxicity. [ABSTRACT FROM AUTHOR]

The use of biosensors for water alert system is critical for providing safe water to the general public. A cathode-shared microbial fuel cell (MFC) sensor array was designed improve the detection credibility by eliminating the cathode performance variation, based on the principle that only the bioanode would be used as the sensing and transducing element. Four integrated MFCs exhibited high parallelism, and independence without the cross contamination or electric signal interference. Two linear ranges were observed (from 0.25 to 0.75 mM and from 1 to 10 mM) for acetate detection. A linear relationship between inhibition ratio ( IR ) and Cu 2+ concentration from 2 to 6 mg/L was recorded. The sensor expressed an immediate voltage decrease when exposed to a pH decrease from 6 to 4. The compact design of the cathode-shared MFC sensor array assure the detection credibility, and the number of the integrated MFC sensors is alterable based on the monitoring requirement. [ABSTRACT FROM AUTHOR]

The application of microbial fuel cell (MFC)-based toxicity sensors to real-world water monitoring is partly impeded by the limited sensitivity. To address this limitation, this study optimized the flow configurations and the control modes. Results revealed that the sensitivity increased by ∼15–41 times with the applying of a flow-through anode, compared to those with a flow-by anode. The sensors operated in the controlled anode potential (CP) mode delivered better sensitivity than those operated in the constant external resistance (ER) mode over a broad range of anode potentials from −0.41 V to +0.1 V. Electrodeposition of Cu(II) was found to bias the toxicity measurement at low anode potentials. The optimal anode potential was approximately −0.15 V, at which the sensor achieved an unbiased measurement of toxicity and the highest sensitivity. This value was greater than those required for electrodeposition while smaller than those for power overshoot. [ABSTRACT FROM AUTHOR]