Microbial Fuel Cells for Wastewater Treatment - Biotechnologies and Biomimetics for Civil Engineering - page 412

expenditure on the materials needed to make a MFC and eliminated the disturbing
biofouling of membrane. However, substantial oxygen diffusion into the anode
chamber in the absence of the PEM could occur to reduce the fraction of electrons
recovered as current.
18.3.3 Other MFC Configuration
Besides the above configurations, a series of variations on these basic designs have
emerged in order to achieve different purposes, such as increase of power density,
achieving continuous flow or nutrient removal. For example, to increase the overall
system voltage, MFCs can be stacked or linked together in series (Aelterman et al.
2006 ). Another type of MFC, nitrifying and denitrifying MFC for decentralized
wastewater treatment was reported by Feng et al. ( 2013b ). Their MFC system was
built on the basis of conventional anoxic/oxic wastewater treatment system and
achieved the continuous flow mode by using a baffle with holes instead of PEM. An
integrated photobioelectrochemical system was constructed by installing a MFC
inside an algal bioreactor (Xiao et al. 2012 ). This system achieves the simultaneous
removal of organics and nutrients from a synthetic solution, and the production
of bioenergy in electricity and algal biomass through bioelectrochemical and
microbiological processes.
18.4 Materials
MFCs are generally made of three major parts: anode, cathode, and PEM (if
present). There are a variety of materials for their construction. Electrode materials
play an important role both in the performance and cost of MFCs. A good anode
material should have the following properties (Logan et al. 2006 ; Zhou et al.
2011 ): large surface area; excellent electrical conductivity, strong biocompatibil-
ity, chemical stability, appropriate mechanical strength and toughness. Up to now,
various materials are used for electrodes including carbon materials, e.g., carbon
paper (Liu et al. 2005a ), carbon cloth, carbon felt (Chaudhuri and Lovley 2003 )
and reticulated vitreous carbon (RVC) (He et al. 2005 ; Rabaey et al. 2005b ),
graphite materials, e.g., graphite granules and graphite fiber brushes (Aelterman
et al. 2006 ; He et al. 2006 ; Rinaldi et al. 2008 ), etc. Since different electrode
materials vary obviously in their physical and chemical characteristics, they have
impacts on microbial attachment, electron transfer, electrode resistance and the
rate of electrode surface reaction. Thus, some strategies could be applied to boost
the performance in terms of increasing the surface area and the biocompatibility.
The anode materials could be fabricated with C/polyaniline (PANI) composites,
carbon nanofibers, or nitric acid carbon activation (Scott et al. 2007 ), or integration
of carbon nanotubes to PNAI (Qiao et al. 2007 ), etc.