Detection of 4-Nitrophenol, a Model Toxic Compound, Using Multi-Stage Microbial Fuel Cells

Abstract

The upstream protection of the biomass present in biological treatment processes is a vital challenge as the consequences of failure could include exposure of water users to hazardous chemicals in addition to loss of treatment performance. Online detection of toxic compounds in wastewater could enable processes to be monitored in real-time and promote pro-active responses to pollution incidents. Recently, Microbial Fuel Cells (MFCs) which generate electricity from organic matter oxidation have shown potential as sensors for online detection of toxicity. In this study, the detection of a model toxicant (4-nitrophenol) was investigated using a multi-stage MFC-based toxicity sensor. MFCs were operated with synthetic wastewater to maintain realistic conditions while enabling organic carbon levels to be controlled. A positive correlation was observed between the 4-NP concentrations and the current drop area showing that the response was proportional to the toxicity level. In addition, the sensor anodic biofilm exhibited resilience to acute toxic events with recovery of 75% of the initial current following a toxic event comprising 500 mg/L 4-NP after 4 h. However, repetitive toxicity events could lead to the selection of resistant bacteria able to degrade the toxic compounds. In this study, a maximal 4-NP degradation rate of 36 mg/h was observed. This limitation could be overcome by re-calibration after a determined number of toxic events. An additional feature of the multi-stage configuration of the sensor is that a drop in output caused by the presence of a toxic compound could be distinguished from a drop in output caused by a decrease in BOD. The microbial community on the sensor anode was characterized by 16S rRNA gene sequencing and shown to comprise an anaerobic community of fermentative bacteria capable of producing volatile fatty acids and hydrogen that were consumed by electrogenic Geobacter spp (2.76 to 21.39% of the anode community) that generated the electrical signal in the sensor. The multi-stage MFC biosensor could provide an early warning system capable of alerting process operators to the presence and level of toxicity in influent wastewater.

No re-calibration required? Stability of a bioelectrochemical sensor for biodegradable organic matter over 800 days

“…Suggestive of competitive anaerobic processes occurring consuming substrate through non-electrogenic pathways, such as biomass production and non-electrogenic degradation of complex substrates to intermediates that were subsequently consumed electrogenically downstream in later stage MFCs. The pattern of electrical output observed with the flow-mode MFCs fed real wastewater could also indicate the presence of toxic compounds ( Godain et al, 2020 ).…”

“…As we have described previously ( Spurr et al, 2018 ), a multi-stage MFC configuration possesses advantages in terms of extending the BOD detection range beyond the capacity/saturation limit of a single MFC and thus extends the potential application to higher strength wastewaters. The ordered response of each staged MFC can further indicate inhibition by toxicity ( Spurr et al, 2020 ; Godain et al, 2020 ) and therefore potentially different substrate responses as well.…”

A Sustainable Approach for the Production of Green Energy With the Holistic Treatment of Wastewater Through Microbial Electrochemical Technologies: A Review

“…Moreover, this MFC sensor demonstrated a proficiency to sense acid toxicity (pH ranging from 4 to 6) and heavy metal (Cu 2+ ) toxicity (ranging from 2 to 8 mg L −1 ) (Jiang et al, 2017). Also, other emergent contaminants like 4-nitrophenol, phenol, and n-butanol, n-cyclohexyl-2-pyrrolidone and, different volatile organic matters and pathogens were successfully detected through MFC-based biosensor (Kannan et al, 2019;Godain et al, 2020;Olias et al, 2020). Therefore, removal of organic, inorganic and emerging pollutants from wastewater with recovery of different economically viable resources through METs can abet this technology toward its commercialization (Khoo et al, 2020;Ahmed et al, 2021).…”

Microbial fuel cells for in-field water quality monitoring

“… 54 After repeated shocks of 4-nonylphenol, a shift in the community towards toxicant tolerant bacteria was observed; the non-electrogenic degradation of 4-nonylphenol increased from 15 to 47%, and the sensitivity of the MFC sensor reduced over time. 55 Similarly, a shift of the biofilm community to weak electrogenic bacteria was seen after prolonged exposed to Cr( vi ), which decreased the electron conversion efficiency in the system. 36 When the anode is embedded in soil or sediment, the anodic biofilm may be more protected from the action of bioactive compounds, since these may be degraded by the microorganisms in the surrounding environment.…”