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).