Oxygen-reducing bidirectional microbial electrodes designed in real domestic wastewater

Abstract

In anode operation, current density up to 6.4 A.m − 2 were produced in real wastewater.• Bioanodes formed in open-to-air reactor gave higher O 2 -reduction current when aerated.• Gammaproteobacteria, Bacteroidia and Clostridia were the three dominant classes.• Clear distinction between the planktonic and sessile microbial populations.• Biofilm microbial population mixed both aerobic and anaerobic electroactive species.

The electrochemical microbial tree: A new concept for wastewater treatment

“…In particular, four of the genera identified here -Cloacibacterium, Pseudomonas, Acinetobacter and Brevundimonas -were also present in bidirectional biofilms, i.e. biofilms able to sustain both exoelectrogenic and electrotrophic behaviours [36]. Such development of numerous bacterial classes and genera known to host electroactive species is another argument in favour of the occurrence of the microbial electrochemical snorkel mechanism.…”

“…The nature of the support (plastic controls vs. carbon-felt EMTs) also clearly affected both the quantity of biofilm and the nature of the microbial populations. As the final remark on this section, it should be emphasized that three of the most abundant classes present in the immersed biofilms -Bacteroidia, Gammaproteobacteria and Clostridia -had previously been found in exoelectrogenic biofilms subjected to intense periodic aeration [36].…”

“…Among the 74 OTUs of this class and the 21 class-affiliated genera, 16 belonged to the Lentimicrobium genus (48 ±1% for the 12-cm-exposed EMTs) and 5 to the Cloacibacterium genus. These facultative anaerobic bacteria accept both oxic and anoxic environments, are electroactive, and are commonly involved in the degradation of organic compounds [34][35][36][37].…”

“…The main genus was Pseudomonas in the biofilms and Acinetobacter in the solutions. Both genera have been described as hosting electroactive bacteria able to perform extracellular electron transfer in aerobic conditions [36].…”

Oxygen supply management to intensify wastewater treatment by a microbial electrochemical snorkel

“…Conversely, when placed in oxic conditions, the electrode releases the electrons by reducing oxygen (cathode). So-called bidirectional microbial electrodes have been shown to be efficient for both oxygen reduction and organic matter oxidation [ 15,16 ]. In Strategy 2, the hope is that the presence of the MES, acting as a bidirectional electrode, will reduce the frequency of aeration compared to current WW treatment bioreactors with no MES.…”