Effects Of Low Temperature On Electricity Production Of MFC And Microbial Community Structure Of Theanode Biofilm

At present our earth has been affecting by the environmental pollution, and people’s lives is especially bounded up with the wastewater treatment in environmental pollution. Then a new technology called microbial fuel cell(MFC) came into the researchers’ vision. It’s a better way of using nutrients in wastewater to produce electricity. However, one of the problems is that it’s difficult to start reactors at low temperatures. And the electricity output is lower than that at appropriate temperature. It determines whether industrialization can be realized by MFC during the development process in the future.In order to solve the problem in MFC, we use cubic single-chamber carbon cloth and stainless steel mesh as cathode,carbon brush as anode. Then continuous vaccination to MFC reactors at different temperatures(4℃,10℃ and 25℃). Electricity generation, treatment efficiency, microbial community structure were researched at low temperature. Based on these experiments, this study also investigated the way of staring up MFC reactors though domesticating inoculums. Aiming at increasing the production of electricity, different temperatures(-20℃, 4℃, 10℃, 25℃) and different times(one week, two weeks) were chosen as domesticate inoculums. The results obtained in this study were as follows:The MFC reactors through continuous vaccination obtain the maximum output voltage were 481 m V, 482 m V, 501 m V at 4℃, 10℃ and 25℃, and successful starting time were 349 h, 377 h, 238.5h at 4℃, 10℃ and 25℃; Under three temperature conditions could reach the maximum power density of 550.55 m W/m2, 669.3 m W/m2 and 808.5m W/m2;The COD removal rates relative to others were not obvious, but in coulomb efficiency differences more obvious, were 37.5%, 28.2%, 43.3%. According to 454 pyrosequencing results we knew that anode microbial community structure were similar at phylum and class level. At the level of genus, continuous vaccination to MFC reactors at 4℃,10℃, 25℃ on the anode biofilm has a big difference. The three samples of S4, S10 and S25 included Proteobacteria、Bacteroidetes、Firmicutes、Spirochaetae and in which Aeromonas, Acholeliasma, Alkaliflexus, Acinetobacter are dominant genus. Aeromonas in S4, S10, S25 are 4.4%, 1.3%, 2.7%; Acholeliasma in S4, S10, S25 are 10.8%, 1.2%, 9.7%; Acinetobacter in S4, S10, S25 are 3.16%, 2.68 %, 4.71%; Alkaliflexus in S4, S10, S25 are 3.6%, 2.2%, 2.48%. We can found Desulfuromonas exists in S4, which did not detect in S10, S25. Anaerovorax(6%) within S4 is higher than that in S10(3.5%) and S25(1.4%), which belongs to the Firmicutes. Armatimonadetes within S4, whose ratio was 7.3%, significantly higher than S10 and S25. This illustrated that some bacterias which are not classified at 4℃ existed on the biofilm of anode. The reason that MFC can work at a low temperature is there being some electrogenesis which can adapt to low temperatures, and they had unique mechanism.In this study MFC reactors was started up at 4℃ through domesticating inoculums at different temperatures and different times. Domesticated inoculums at 4℃ for one week, MFC had the maximum output voltage of 461 m V at running 728h; Domesticated inoculums at 4℃ for two weeks, MFC reach the maximum output voltage of 474 m V at running 1170 h were found in this study. The maximum power density of domesticating inoculums at 4℃ for one week and two weeks were 526 m W/m2 and 650 m W/m2. The maximum output voltage of domesticating inoculums at 4℃ for one week and two weeks were 564 m V and 588 m V. Different temperatures acclimation inoculums at COD removal have little impact, but in terms of the coulomb efficiency had huge ascendancy. The coulomb efficiency of domesticating inoculums at 4℃ were 68.2%,higher than that didn’t domesticate inoculums of 29.4%.However,-20℃ is not a suitable option for acclimating activated slude. The low temperature(-20℃) extended time of staring up MFC reactors, and made a poor electricity production performance of the output voltage, power density, ect.Starting up MFC reactors at a low temperature(4℃) was successfully achieved in this experiment, and the electricity production performance was comparatively ideal. An effective method of starting up MFC reactors at a low temperature(4℃) was found through domesticating inoculums, and a wide range of applications in wastewater treatment technology was achieved.