Page 278 - Industrial Wastewater Treatment, Recycling and Reuse

252 Industrial Wastewater Treatment, Recycling, and Reuse

neutral redox microenvironment irrespective of the external pH (Kim and
Gadd, 2008). The external pH can bring alterations in the microbial activ-
ities, including synthesis of biomolecules and ion transport across mem-
branes. MFC performance also depends on the redox conditions of
fermentation (anolyte). External acidophilic pH is defended by the excessive
+
production of acid-shock proteins that consume the H entering into the
cell and bring the internal pH to near neutral. Extreme alkalophilic pH
+
+
can defend the function of an Na /H antiport pump, which converts
the proton motive force to the sodium motive force (Kim and Gadd,
2008). The exocellular electron transfer to the anode is dependent on the
operating pH, which creates a proton gradient between the cell interior
and surrounding environment. Higher performance was reported at an aci-
dophilic pH over neutral and basic pH in diverse configurations of the MFC
(Raghavulu et al., 2009a,b). The electron transfer is independent of external
pH when the circuit is connected against resistance. The closed circuit cre-
ates a strong proton motive force on to the anode due to the continuous
reduction of protons with the electron acceptor in the terminal reaction.
Moreover, the metabolic activities of biocatalyst will be higher, and waste
remediation also favors neutral pH.
Most of the MFC research is confined to the operation of an anodic
chamber in anaerobic microenvironments, but a few reports are also avail-
able on the application of aerobic metabolic functions at the anode
(Ringeisen et al., 2007; Rodrigo et al., 2007; Venkata Mohan et al.,
2008f). If a low level of oxygen is allowed in the anode chamber, such that
it cannot neutralize all the electrons generated in the system, the remaining
electrons can be harnessed. This has an added advantage of higher treatment
efficiency, including some toxic compounds (dyes and colored compounds)
that need sequential alternative microenvironments. Overall, high carbon
concentration, low oxygen levels, and the least possible distance between
the anode and the cathode are the prerequisites for power generation from
the aerobic MFC. However, detailed studies pertaining to understanding the
process are required to establish the advantages of oxygen presence at
the anode.

6.4.2 Bioelectrochemical Treatment
MFC operation has documented efficient waste remediation compared to
conventional anaerobic treatment process (Aelterman, 2009; Bond et al.,
2002; Chae et al., 2009; Chandrasekhar and Venkata Mohan, 2012;