4.6 Variation of voltage generation and AVS reduction in the
field
The field test in the marine sediment in the Yamaguchi bay was carried
out in a similar size of the laboratory SMFCs. It was interesting that
the AVS reduction trend was similar in the field, however, the voltage
generation is not similar with the laboratory experiments. The voltage
generation was higher in the field than the laboratory experiments for
the similar size SMFCs. The probable reason of this trend is that the
various nutrients supply in the intertidal region naturally and that
might increase the activities of the bacteria and hence increase the
voltage. The tidal effect and the other environmentl factors such as
solar radiation could also affect the power generation in the field.
This was the first time to compare the voltage generation between the
laboratory experiment and field experiment with the similar SMFC in the
high sulfide content contaminated sediment. Kubota et al. 2019 showed
that AVS value has reduced in the Tokyo bay tidal flat sediment during a
field test in the high eutrophic water enclosed bay.
By utilizing the SMFC, the rate of flow of electrons can be probably
increased and the process of AVS (mainly FeS and H2S)
reduction will be increased. The resulting electron flows promote
remediation of sediment by enhancing physicochemical and microbial
metabolic reactions. So the voltage generation and the AVS reduction
were happened together in the field experiment (Erable et al., 2017).
Though the vaoltage and power generation is higher in the field but the
seasonal temperature variations could be a factor in the field to supply
power to the environmental monitoring sensors. This present field test
was carried out in relatively warm (ambient temperature varied from
20-250 C). The field test during the winter might show
some lower power generation due to the lower surrounding temperature. In
this particular research, the similar size single anode SMFC was used
both in the laboratory and the field experiments. The series connection
of the SMFCs could increase the voltage and power generation and hence
could be a potential source of power supply to the various
geo-environmental monitoring sensors. The mechanisms of the AVS
reduction was discussed in details in our previous paper (Moqsud 2020).