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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]

[Display omitted] • Synchronous removal of gaseous toluene and benzene were achieved by MFC-BTF. • Shifts of mass transfer and microbial community for VOCs removal were revealed. • The removal of benzene was stimulated with the presence of toluene in exhaust. • Various biodegradation pathways for toluene and benzene were proposed. Illustrating the biodegradation processes of multi-component volatile organic compounds (VOCs) will expedite the implication of biotechnology in purifying industrial exhaust. Here, performance shifts of microbial fuel cell and biotrickling filter combined system (MFC-BTF) are investigated for removing single and dual components of toluene and benzene. Synchronous removal of toluene (95 %) and benzene (97 %) are achieved by MFC-BTF accompanied with the output current of 0.41 mA. Elevated content of extracellular polymeric substance facilitates the mass transfer of benzene with the presence of toluene. Strains of Bacteroidota , Proteobacteria and Chloroflexi contribute to the removal of dual components VOCs. Empty bed reaction time and the VOCs concentration are the important factors influencing their dissolution in the system. The biodegradation of toluene and benzene proceeds with 2-hydroxymuconic semialdehyde and o-hydroxybenzoic acid as the main intermediates. These results provide a comprehensive understanding of multi-component VOCs removal by MFC-BTF and guide the system design, optimization, and scale-up. [ABSTRACT FROM AUTHOR]

This study employed an open external circuit, rather than a closed circuit applied in previous studies, to operate an microbial fuel cell (MFC) sensor for real-time nitrate monitoring, and achieved surprisingly greater sensitivity (4.42 ± 0.3–6.66 ± 0.4 mV/(mg/L)) when the nitrate was at a concentration of 10–40 mg/L, compared to that of the MFC sensor with a closed circuit (0.8 ± 0.05–1.6 ± 0.1 mV/(mg/L)). The MFC sensor operated in open circuit (O-MFC sensor) delivered much more stable performance than that operated in closed circuit (C-MFC sensor) when affected by organic matter (NaAc). The sensitivity of O-MFC sensor was twice that of C-MFC sensor at a low background concentration of organic matter. When organic matter reached a high concentration, the sensitivity of O-MFC sensor remained at an acceptable level, while that of C-MFC sensor dropped to almost zero. Challenged by a combined shock of organic matter and nitrate, O-MFC sensor delivered evident electrical signals for nitrate warning, while C-MFC failed. Another novel feature of this study lies in a new mathematical model to examine the bioanode process of nitrate monitoring. It revealed that lower capacitance of the bioanode in O-MFC was the major contributor to the improved sensitivity of the device. [ABSTRACT FROM AUTHOR]

An early warning system is important to guarantee human health and ecological safety. Microbial fuel cell (MFC) sensor can achieve a self-sustainable monitoring without additional transducer or power sources. It would not limited by the main bottleneck of other contemporary MFC technologies, i.e., the low current density output, and is believed one of the most promising applications in the niche market of MFC technologies. This review is limited to MFC sensors for water quality early warning systems only, with emphasis on biochemical oxygen demand (BOD) and toxicity sensors. A comprehensive summary and discussion on sensor fabrication, operation, data representation, and optimization are provided. The MFC sensor is particularly promising to serve as a self-powered sensing device for in-situ and on-line environmental monitoring, as proved both in laboratory and field test. In addition, the main hurdles and future perspectives are discussed, as well as potential future research, which includes the following: separately lowering the detection limit or improving the concentration range dependent on the application of MFC for organic matter monitoring; further improving the sensitivity as well as lowering the recovery time of biofilm after a certain shock; developing the kinetic and/or empirical model in combining with the detection algorithm to distinguish the signal interference of complex aquatic environment, especially when the shock of BOD and toxicity occur simultaneously. [ABSTRACT FROM AUTHOR]

Limited access to the hydrophobic organic compounds by microorganisms impedes the improvement of performance of bioreactor processing contaminant degradation. Here, we assembled activated carbon in the anode chamber of the microbial fuel cell (MFC) to serve as a reservoir for toluene molecular and exoelectrogens. The adsorption of toluene by activated carbon facilitated the substrate accessible by exoelectrogens and was beneficial for toluene biodegradation. Rapid degradation of toluene was achieved by MFC assembled with active carbon anode (AC-MFC) in 36 h, which was shorter than that (∼60 h) for MFC with carbon felt anode (CF-MFC). In addition, significant decrease of gaseous toluene released from anolyte into headspace as the introduction of activated carbon. The model EABs Geobacter anodicances was enriched on activated carbon, which brought out the elevated performance of AC-MFC for toluene degradation and power generation. Polarized curves revealed that the maximum power density of AC-MFC was 3328 mW/m3, which was 2.6 times higher than that of CF-MFC (1267 mW/m3). Analysis of anolyte revealed that benzoic acid, dihydroxybenzoic acid and β-carboxy-cis-cis-muconate were the main intermediate products during toluene degradation. This work provides an effective strategy for improving biodegradation efficiency of hydrophobic organic compounds accompany with power generation. [Display omitted] • Toluene accessibility for exoelectrogens was improved in anode of MFC. • A significant amount of Geobacter anodireducens was enriched on activated carbon. • The adsorption of toluene impeded the escape of toluene from anolyte. • A high ability to electron delivery was obtained for the bioanode. [ABSTRACT FROM AUTHOR]