Psychrophilic Bacteria Isolation And Electricity Production Enhancement In Microbial Fuel Cells Under Low Temperature

Nowadays we can see huge growing demand for energy over the world hereat power resources are exhausted,hence alternative energy sources are very essential last years.Despite that amount of fossil fuel is enough to daily needs their output can have serious negative social and ecological after-effects.Mining of such fossil fuel as oil,gas will be more complicated in the nearest future because of high financial spending and ecological consequences.At the same time ability to get cheap and reliable energy has key importance for the improving life quality and for the economic development.Renewable and pure type of energy is essential demand of modern society.Investigations in the field of Microbial fuel cells(MFC)could help in this situation in both occasions.MFC is new process which both can generate electricity and deplete organic substances from the waste water.During five last years the interests to the MFC as an alternative energy sources have increased.Currently majority of investigations were made under room or higher temperature conditions(20-35oC).When the reactor temperature is lower,the mesophilic bacterial consortia goes through a long selection and adaptation process during which their activity slows down drastically,explaining the behavior of digesters installed in areas characterized by large seasonal temperature differences,where winter can sometimes stop production.There is also a group of bacteria called psychrophilic bacteria that naturally prefer low-temperature environments.A microbial community capable of providing electricity generation yields at low temperatures would promote a great advance in wastewater treatment for cold areas where average annual temperature is between 8 and 10 oC or even lower,with no big seasonal changes.Therefore,for successful applying MFC in practice,we need to find the bacteria type that is adapted to various environments and have a capacity for growth over a wide range of temperature.In this research we have a goal to optimize MFC for usage at low temperatures range(5-15oC)which implies finding the right construction design and cultivating right bacteria strains adapted to such environment.It was found that starting reactor at low temperature forces psychrotoleran bacteria colony to be developed.In result such reactors can successfully run at varying temperatures from 5 oC to 25 oC without significant performance changes.Additionally,two MFC designs have been compared in this research – single and double chamber reactor.Single-chamber reactor produced output current close to constant voltage(540 ~ 560 m V)at both low and room temperatures whereas double-chamber reactor failed to produce good results after switching from room temperature to low temperature.At the same time,double chamber reactors have higher internal resistance-200 ? against 155 ? for single chamber reactor-and are more complex in production.Therefore,the conclusion was made that single-chamber reactor design are more suitable for practical application.Experimental data efficiency of microbial fuel cell bioaugmentation of Klebsiella sp.,Shewanella sp.and Enterobacter sp.at low temperatures can give the maximum power density.The results implied that the bioaugmentated mixed-culture MFC sustainably performed better than the pure-culture(Shewanella)MFC at 10°C,but the electrogenic activity of anodic bacteria was substantially reduced at the lower temperature of 5°C.At 10°C,the maximum output voltage generated with the mixed-culture was 540–560 m V,which was 10%–15% higher than that of pure culture Shewanella MFCs.The maximum power density reached 465.3 ± 5.8 m W/m2 for the mixed-culture at 10°C,while only 68.7 ± 3.7 m W/m2 was achieved with the pure-culture.It was shown that the anodic biofilm of the mixed-culture MFC had a lower overpotential and resistance than the pure-culture MFC.The bioaugmentation was applied in order to accelerate startup of three typical varieties of microbial fuel cell at low temperatures.At low temperature of 5oC,the highest output voltages of Klebsiella sp.Shewanella sp.and Enterobacter sp.enhanced MFCs were 700 m V,660 m V and 560 m V respectively.Furthermore,the annual temperature cycle was modeled by varying environment temperature and all three bioaugmented MFC showed the stable performance in such conditions.Based on these results we can conclude that bioaugmentation with Klebsiella sp.,Shewanella sp.and Enterobacter sp.is a new promising technique to increase energy production of MFC in a setback.