4.1 Variation of current with time
Figure 2 illustrates that the variation of voltage with duration in the laboratory experiment. It is seen that all the three marine sediments showed the higher value of voltage than the river sediments. Sample 3 showed the peak voltage and reached at around 300mV after 1 week. Sample 1 and sample 2 showed the similar trend of voltage generation with sample 3. The initial rate of voltage generation was higher as the bacteria got ample of food during the early stage of laboratory experiments. After reaching at the peak the voltage generation reduced and almost constant for another 2 weeks. However, voltage generation was always lower in the case of river sediment. Though the organic content of the river sediment was little bit higher than the marin sediment, the grain size of river sediment was larger and consequently affect the voltage generation. The peak voltage generation in river sediment was 140 mV which was 60% lower than the sea sediments. The high electrical conductive saline water of sea could be another reason for the higher value of voltage in the sea sediment (Song and Jiang, 2018). The external resistance used in this particular research was 100 Ω both in the lab and the field. So, the peak power output from one cell is around 28 mW/m2 . Wang et al., 2014 showed that the voltage generation can be great influenced by the organic content present in the sediment. However, our results showed that the power generation was always higher in the sea sediment instead of river sediment. The particle size and the salinity affected the results more significantly than the organic content of the sediment.