|M.Sc Thesis||Department of Civil and Environmental Engineering|
|Supervisor:||Assoc. Prof. Armon Robert|
|Full Thesis text - in Hebrew|
As fossil fuel supplies dwindle and greenhouse gas emission rates accelerate, there is a major need for new green groundbreaking sources of energy from renewable carbon-neutral compounds with minimal negative environmental impact. Microbial fuel cell (MFC) technologies represent a relatively new approach for electrical power generation by using microorganisms as catalysts that convert chemical energy stored in organic substrates into electrical one by oxidation and reduction reactions at solid-states electrodes. Their widespread applications are simultaneous wastewater treatment and electricity production, power sources for environmental sensors and environmental bioremediation. The performance of MFC depends on a combination of physical and mechanical parameters that need to be improved and adapted in order to obtain the most efficient and practical device.
The main goal of our study was to investigate and characterize anodic processes occurring in one-compartment electrochemical cell simulating MFC conditions in order to achieve enhanced electrical power. For this purpose, we used: a) High specific surface area electrode material that can directly affect bacterial attachment and electron transfer. b) Different types of electroactive bacteria: E. coli CN13; E. coli K12 and Shewanella oneidensis MR-1 that can enhance power production. c) Soluble and new non-soluble Prussian blue electron mediator.
By means of scanning electron microscopy (SEM) and polarization measurements our study demonstrates that obtained electrical current is more significant as specific surface area of working electrode is higher. Additional improvement in getting high electrical parameters was achieved using new Prussian blue mediator immobilized on layered electrode surface by electrodeposition technique. On the contrary, the soluble Methylene blue electron mediator used in our electrochemical cell allows us getting even higher electrical currents than previously. Explanation of this fact is that immobilized mediator is not available for all bacterial layers of investigated biofilm.
Another important finding was demonstration of hair like appendages in E. coli K12 strain resulted in enhanced electrical current (7.12 mA) compared to E. coli CN13 strain (3.7 mA) that lacks this attribute. Shewanella oneidensis MR-1 reported as electroactive bacteria by using conductive “nanowires”, provided the most significant electrical current (27.9 mA) in our integrative system. Finally, structural analysis of the formed biofilm was performed by confocal laser scanning microscopy (CLSM) using image quantification software PHLIP. This method showed that there is a linear relationship between electrical current value and amount of viable bacterial whole cells.