Abstract
Microbial fuel cells (MFCs) have been tentatively applied for wastewater treatment, but the presence of nitrogen, especially nitrate, induces performance instability by changing the composition of functional biofilms. A novel denitrifying exoelectrogenic strain EB-1, capable of simultaneous denitrification and electricity generation and affiliated with Mycobacterium sp., was isolated from the anodic biofilm of MFCs fed with nitrate containing medium. Polarization curves and cyclic voltammetry showed that strain EB-1 could generate electricity through a direct electron transfer mechanism with a maximum power density of 0.84 ± 0.05 W m−2. Additionally, anodic denitrification, as a concurrent metabolism, was demonstrated with an efficient removal rate of 0.66 ± 0.01 kg N m−3 d−1 at a COD/N ratio of 3.5 ± 0.3. Importantly, voltage output was not negatively influenced by nitrate, indicating that the concurrent process of nitrate removal and electricity generation was a limitation of the electron donor rather than an inhibition of the system. Furthermore, various organic materials were successfully utilized as anode donors for strain EB-1, and demonstrated the exciting performances in terms of simultaneous denitrification and electricity generation. Mycobacterium sp. EB-1 thus expands the diversity of exoelectrogens and contributes to the potential applications of MFC for simultaneous energy recovery and wastewater treatment.
Highlights
During the past two decades, microbial fuel cells (MFCs) have drawn global attention since they exhibit a high potential for pollutant removal and power generation
Once exoelectrogenic denitrifying biofilms (EDBs) were enriched from the anode of MFCs fed with acetate containing mineral salt medium (MSM), the EDBs were used to isolate denitrifying exoelectrogens using an improved method based on a dilution plating procedure (Xing et al, 2010)
Phylogenetic analysis based on the 16S rDNA gene indicated that strain EB-1 belonged to phylum Actinobacteria and had the closest match to Mycobacterium fortuitum CT6 and Mycobacterium sp
Summary
During the past two decades, microbial fuel cells (MFCs) have drawn global attention since they exhibit a high potential for pollutant removal and power generation. In MFCs, electrogenic bacteria oxidize organic pollutants and release electrons to the anode. Electrons flow through the external circuit to the cathode, react with certain acceptors, and generate electricity. Wastewater treatments using MFCs mainly focus on organics removal; nitrogen is present in wastewater and poses a considerable threat to lakes and other natural water bodies. It is necessary to construct an MFC for simultaneous removal of organics and nitrogen. Efficient nitrogen removal has been achieved at both the biocathode of dual-chamber
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