A rechargeable microbial electrochemical sensor for water biotoxicity monitoring

Microbial electrochemical sensor has been regarded as a promising technology for water biotoxicity monitoring, while its practical application is partially restricted by the requirement of organic substrate or power supply in real time. In the present study, rechargeable microbial electrochemical sensors were constructed, with the ex-situ preparation of bioanode and the in-situ preparation of biocathode. Acetate, formate, and hydrogen were identified as the charge carriers, and a Coulombic efficiency of 38% ± 18% and an energy efficiency of 2.2% ± 0.7% were obtained. The increase of charge current could decrease the energy efficiency as well as maximum acetate accumulation, while increase the H2 component. The increase of discharge resistor could enhance the energy efficiency, while had little impact on the Coulombic efficiency. Good reusability of rechargeable biosensors was observed with an injection of formaldehyde from 0% to 0.05%, but the sensors could not be fully recovered after the injection of 0.1% formaldehyde. The exposure of formaldehyde could affect the relative abundance of Acetobacterium, Acetoanaerobium, and Geobacter. When an abiotic cathode was used, the formate and hydrogen produced during the charging process were converted into acetate as an intermediate product during the discharging process. This study demonstrates the potential of the rechargeable microbial electrochemical system as a novel sensor for water biotoxicity monitoring. [Display omitted] •Rechargeable microbial electrochemical sensors were constructed.•Acetate, formate, and hydrogen were identified as the charge carriers.•The effect of charge current and discharge resistor was investigated.•Good reusability of rechargeable biosensors was observed.•Acetate was an intermediate product when using an abiotic cathode.