RESUMO
Bioelectrochemical systems which employ microbes as electrode catalysts to convert chemical energy into electrical energy (or conversely), have emerged in recent years for water sanitation and energy recovery. Microbial biocathodes, and especially those reducing nitrate are gaining more and more attention. The nitrate-reducing biocathodes can efficiently treat nitrate-polluted wastewater. However, they require specific conditions and they have not yet been applied on a large scale. In this review, the current knowledge on nitrate-reducing biocathodes will be summarized. The fundamentals of microbial biocathodes will be discussed, as well as the progress towards applications for nitrate reduction in the context of water treatment. Nitrate-reducing biocathodes will be compared with other nitrate-removal techniques and the challenges and opportunities of this approach will be identified.
Assuntos
Fontes de Energia Bioelétrica , Purificação da Água , Nitratos , Eletricidade , Águas Residuárias , EletrodosRESUMO
Microbial electrodes were designed in domestic wastewaters to catalyse the oxidation of organic matter (anode) and the reduction of oxygen (cathode) alternately. The successive aeration phases (cathode) enhanced the anodic efficiency, resulting in current densities of up to 6.4 Am-2 without the addition of any substrate. Using nitrogen during the anodic phases affected the microbial populations and the electrodes showed a lower ability to subsequently turn to O2 reduction than the microbial anodes formed in open-to-air conditions did. No strong difference was observed between internal and external biofilm, both of which showed a very large variety of taxa in terms of abundance as well as variance. They comprised a mix of aerobic and anaerobic species, many of which have already been identified separately in bioelectrochemical systems. Such a large diversity, which had not been observed in aerobic bidirectional bioelectrodes so far, can explain the efficiency and robustness observed here.