Environmental Engineering Reference
In-Depth Information
excellent power generation, as large concentrations of highly colored mediators
from this reactor were detected (Logan and Regan 2006a ).
However, there are complicated organic matters in wastewater and complex
metabolisms such as fermentation could get involved in MFCs. Molecular char-
acterizations of anodic communities with complex wastewater sources revealed a
high diversity of microbial species, dominant with a- (Phung et al. 2004 ), b- (Kim
et al. 2004 ; Phung et al. 2004 ), and c-Proteobacteria (Logan et al. 2005 ). For
example, the characterization of anodic communities present in a two-chamber
MFC treating chocolate wastewater showed a high percentage of b-Proteobacteria
(51 %) (Patil et al. 2009 ). Whereas, microbial communities that developed by
MFCs supplied with winery or potato wastewater, were a mixed consortia pre-
dominated by Geobacter sulfurreducens, representing 44 % and 60 % of 16S
rRNA gene clones, respectively (Cusick et al. 2010 ; Kiely et al. 2011a ). Most
importantly, a large proportion of clones is uncharacterized in these mixed-culture
systems, especially with complex wastewater sources. The lower frequency to
detect known exoelectrogens implies a greater diversity of this phenotype than
presently realized. The significance of the potential function of these dominant
community members is still unknown.
Cultivation mode including fed-batch and continuous flow could affect
microbial communities as well. In a continuous flow mode MFC supplied with
acetate, the composition of anodic community revealed that the most dominant
phyla were Proterobacteria (23-33 %), Bacteroidetes (17-40 %) and Chloroflexi
(21-30%) on the basis of 454 pyrosequencing technique (Feng et al. 2013b ). In an
upflow system, a large number of methanogenic archaea in the mixed biomass
appeared on the anode based on fluorescence in situ hybridization (He et al. 2005 ).
Literature studies have demonstrated that d-Proteobacteria (50-90 %) were
dominant in the anode community of sediment MFC (Bond et al. 2002 ; Bond and
Lovley 2003 ), while Cytophagales (up to 33 %), Firmicutes (11.6 %), and
c-Proteobacteria (9-10 %) were the minor components in the anodophilic con-
sortia (Tender et al. 2002 ; Holmes et al. 2004 ).
18.8 The MFC's Full-Scale Applications
The development of MFC's practical application is still in the early stage. To date,
most MFCs have been investigated in the bench-scale, generally less than 1 L and
produced a maximum potential approximately 0.8 V. Apparently, the power
density and MFC configuration have not yet reached a widely applicable level,
remaining the challenging obstacle.
Sediment MFCs have been demonstrated at scales effective to be an alternative
renewable power source in seawater applications (Bond et al. 2002 ; Lowy et al.
2006 ; Dewan et al. 2014 ). According to Fig. 18.5 , in principle sediment MFCs
consist of two electrodes made of conductive material. The anode is buried under
Search WWH ::




Custom Search