1. INTRODUCTION
We need green energy which could be a sustainable source for the power supply to the environmental monitoring sensors such as temperature sensors in the remote intertidal zone (tidal flats) in Japan and other places. Depletion of energy reserves, global warming and the concern of environmental pollution are inspiring the search for new environment friendly and sustainable energy production methods all over the world. Renewable bio-energy is viewed as one of the ways to alleviate fuel needs of the future and to overcome the crisis of global warming.
Microbial Fuel Cell (MFC) is the bio-electrochemical device that converts microbial reducing power into electrical energy which is a green and safe source of bioelectricity (Logan & Regan, 2006; Hong et al., 2009; Moqsud 2020). They use the existing substrates from renewable sources and convert them into harmless by-products with simultaneous production of bioelectricity (Habermann W. & Pommer, E.H., 1991). In this way, bioelectricity production employing MFC has generated considerable interest in both basic and applied research in recent years. Moqsud et al., (2014) tried to get bioelectricity from various organic wastes and also living plants by using MFC technology.
SMFCs are being considered for use as a potential power source for aquatic water quality sensors such as pH, temperature, and dissolved oxygen sensors (Moqsud 2020; Moqsud et al., 2017). SMFC can be a potential source of remediation of this problem. The geo-bacteria (which live in soil) break the organics in the soil and consequently generate the bioelectricity. Abbas et al., (2017) found that SMFCs could be a source of sustainable energy and heavy metal remediation. To change the batteries from the environmental monitoring sensors of this contaminated tidal flat is a serious problem and often the solar system is not working due to the bad weather or other reasons.
The major objective of this study is to generate bioelectricity from a contaminated sediment while improving its geoenvironmental condition in the laboratory experiment and to compare it through field experiment of SMFCs.
2. METHODS AND MATERIALS
2.1 SAMPLE COLLECTION
Four samples were collected for this experiment from Yamaguchi bay at depths of 0-20 cm from tidal flat and the river areas during the ebb tide. A ponar dredge sediment sampler was used to collect the samples. Sample 1, 2 and 3 were collected near the intertidal zone of Yamaguchi bay (33.93 N, 131.22 E), Ube city. Sample 4 was collected from the river near that tidal flat area (33.93 N, 131.22 E) to compare the marine sediments SMFCs and the river sediment SMFCs. The samples were collected middle of May, the average ambient temperature is around 250C. The geoenvironmental condition of the Yamaguchi bay tidal flat area is not good due to the various human activities. The smell of the sediment was unpleasant and there is very small signs of benthos in the sediment. The AVS value is more than suitable range in different parts of the Yamaguchi bay and hence caused the declination of catch of shell and decrease of the horseshoe crab has been observed (Moqsud et al., 2017). This is a serious ecological problem and the researchers are trying to solve this problem.
Table 1 summerises the basic physico-chemical properties of the four sediments. From the grain size analysis of the four sediments, it was observed that all the three sea sediments showed the similar trend, however, the river sediment showed a different trend and the particle size is larger than the sea sediments. It was seen that the loss on ignition (LOI) which is the indicator of organic content was relatively lower in sea sediments (sample 1, 2, 3) 12% than in the river sediment 14% (sample 4). The AVS value was also higher in the case of marine sediments (more than safe limit , 0.2 mg/g-dry mud). Anaerobic bacteria (sulfate reducing bacteria) reliably to generate AVS by converting the sulfate to sulfide and is one of the major indicators for the geoenvironmental condition (Rickard & Morse, 2005). In this study, the AVS value will be taken as a key indicator of the geo-environmental condition improvement. According to the Japanese fisheries research association, the safe value for AVS is 0.2 mg/g dry mud for the benthos living in the mud.