Abstract
The capacity of electroactive bacteria to exchange electrons with electroconductive materials has been explored during the last two decades as part of a new field called electromicrobiology. Such microbial metabolism has been validated to enhance the bioremediation of wastewater pollutants. In contrast with standard materials like rods, plates, or felts made of graphite, we have explored the use of an alternative strategy using a fluid-like electrode as part of a microbial electrochemical fluidized bed reactor (ME-FBR). After verifying the low adsorption capacity of the pharmaceutical pollutants on the fluid-bed electrode [7.92 ± 0.05% carbamazepine (CBZ) and 9.42 ± 0.09% sulfamethoxazole (SMX)], our system showed a remarkable capacity to outperform classical solutions for removing pollutants (more than 80%) from the pharmaceutical industry like CBZ and SMX. Moreover, the ME-FBR performance revealed the impact of selecting an anode potential by efficiently removing both pollutants at + 200 mV. The high TOC removal efficiency also demonstrated that electrostimulation of electroactive bacteria in ME-FBR could overcome the expected microbial inhibition due to the presence of CBZ and SMX. Cyclic voltammograms revealed the successful electron transfer between microbial biofilm and the fluid-like electrode bed throughout the polarization tests. Finally, Vibrio fischeri-based ecotoxicity showed a 70% reduction after treating wastewater with a fluid-like anode (+ 400 mV), revealing the promising performance of this bioelectrochemical approach.
Highlights
The synthetic chemical industry produces effluents with a high level of salinity and a high chemical oxygen demand (COD), which eventually generates a dispersed pollution problem in the form of micropollutants, called emerging contaminants (EC) (Queiroz et al, 2019)
It has been suggested that biological treatment is not recommended for treating wastewater with a high concentration of CBZ and SMX since such pharmaceutical compounds can inhibit the biological activity of microorganisms present in conventional activated sludge (CAS) treatments (Li et al, 2013)
The microbial electrochemical fluidized bed reactor (ME-FBR) was fed with synthetic wastewater once a day, so its operation mode can be considered semi-continuous with 3.2 days of hydraulic retention time (HRT)
Summary
The synthetic chemical industry produces effluents with a high level of salinity and a high chemical oxygen demand (COD), which eventually generates a dispersed pollution problem in the form of micropollutants, called emerging contaminants (EC) (Queiroz et al, 2019). Anaerobic MBR (AnMBR) have been evaluated, increasing the CBZ and SMX removal up to 80% (Cheng et al, 2018) Operational problems such as membrane biofouling, high costs associated with membranes, and the high energy requirements for both technologies had limited the scale-up of these technologies for treating wastewaters polluted with pharmaceutical compounds (Hai et al, 2011; García-Gómez et al, 2016; Cheng et al, 2018). Considering the relatively high removal of these pharmaceutical compounds under advanced anaerobic treatments as AnMBR, it seems reasonable to explore technological solutions where microbial communities play a crucial role In this context, microbial electrochemical technologies (MET) have been recently classified as one the most promising for achieving sustainable bioremediation in a different environmental niche (Wang et al, 2020). The treated water’s ecotoxicity was monitored to assure the final quality of the effluents
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