3.4. Process monitoring
3.4.1. Bio-electrochemical evaluation
Bio-electrochemistry involves the understanding of anodic biocatalyst
mediated redox catalytic phenomena coupled with charge
separation and charge transfer, which can take place evenly in
solution, or heterogeneously on electrode surfaces. Electrode reactions
generally take place in the interfacial region between solution
and electrode where charge delivery differs from that of the
bulk phases. The electrode acts as e acceptor and can be affected
by the structure and nature of electrode. Nevertheless, the change
in charge distribution during fuel cell operation is due to the substrate
metabolism and nature of the biocatalyst (microorganism).
Few microbial species have the capability to discharge reducing
powers (e and H+) generated during the metabolic activity via
bacterial (biocatalyst) membrane bound organelles or soluble
mediators. In situ evaluation of e discharge employing CV (Vs
Ag/AgCl (S)) with time helps to understand the metabolic shifts
and the carriers involved in e transfer. Electrochemical evaluation
visualized marked variation in e discharge properties with respect
to time (Fig. 4a). SBES documented higher catalytic currents (oxidation,
130.26 mA; reduction, 18.39 mA) at 20th day of operation
followed by 10th day (oxidation, 78.07 mA; reduction,
19.12 mA), 0th day (oxidation, 32.18 mA; reduction, 16.21 mA)
and 30th day (oxidation, 16.72 mA; reduction, 14.17 mA) in both
oxidation and reduction sweeps. Nevertheless, oxidation was quite
higher than reduction in SBES operation. This is a direct evidence of
the association of electrochemically active bacteria (biocatalyst)
with the native mixed consortia avoiding the e losses prior to
reaching the electrode (anode).