Performance And Microbial Community Of The Flat Anode Microbial Fuel Cells

Microbial fuel cell(microbial fuel cell,MFC),as a type of device which can convert chemical energy into electrical energy directly,breaks the concept of traditional organic wastewater treatment,and can convert biomass into energy and resource during degradation of pollutant substance.The microbial community and its metabolism is one of the key factor to affect the performance and function of the MFC reactors,and the research of the microbial community has very important theoretical and application values.Flat anodes are a good tool for studying microbial communities because they can be observed in situ and sequenced in the small region of the anode.However,the cost of flat anode materials is high and the modification method is complicated,which restricts its development and research.The microbial community characteristics of flat anode MFC s in different parts has been studied in this paper,which has very important theoretical value to reveal the influence of microbial community characteristics on the performance of the MFCs.This study compared the performance of MFCs with different configurations,the anode materials and cathode materials were selected and tested.On the basis of which the indium tin oxide(ITO)glass and graphite plate were chosen as anode basement to study the community structure of microbial fuel cells.The distribution of microbial communities in different electrodes was analyzed by using the second generation high-throughput sequencing technique in order to explore the relationship between the characteristics of the microbial communities and the performance of reactors.In this paper,the performance of the carbon brush anode MFC with different configuration is studied and the selection of electrode material is made firstly.The results show that the single-chamber MFC presents simple structure,high environment temperature stability,excellent power generation capacity and high COD removal efficiency,which is more suitable for the present research.Indium tin oxide coated glass(ITO)and flexible graphite plate exhibit the highest stable voltage and have been chosen as the plate anode materials for subsequent tests,both of those have unique advantages such as simple preparation process,easy access and low cost.In addition,this paper compares the performance of two air cathodes,the power density of platinum carbon(Pt/C)cathode MFC is 17%higher than that of activated carbon roller pressed cathode,but the cost of roller pressed cathode is only one-tenth of the Pt/C cathode,both of which have advantages and are used in subsequent studies.The pretreated ITO anode and flexible graphite plate were used as anode materials to construct the MFCs and their performance was examined.The results show that the simple acid and alkali treatment can improve the properties of the ITO anode.The MFC with ITO anode of 2 minutes'acid treatment exhibited maximum voltage of 470 mv,COD removal efficiency of 56%,the MFC has the power density of 253 mW/m~2 based on anode calculation,which is about 16 times higher that of the carbon brush anode(16 mW/m~2).The alkali treated ITO anode obtained similar effect to acid treatment,the MFC with the alkali treated ITO anode exhibits the power density of 271 mW/m~2 based on anode calculation,COD removal efficiency of 54%.The MFC constructed with flexible graphite plate as anode shows the power density of 274 mW/m~2 based on anode calculation.COD removal efficiency of the MFC is54%,higher than that of MFC with carbon brush anode.The bacteria and archaea in different parts of the MFC reactor were collected and the distribution of bacteria and archaea was analyzed by high-throughput sequencing.It has been found that the low-cost industrial materials with simple treatments have excellent enrichment capacity of electroactive microorganism.Bacterial community analysis of the electrode surface shows that in the reactor of acid treated ITO anode,the genus with the highest content on the anode is the genus Geobacter(37.1%-52.4%)of the Proteobacteria phylum,which is positively correlated with the power production capacity of the reactor.The bacteria with the highest content on the cathode was the genus Alkaliflexus of the Bacteroides,with the content of more than20%.In addition,Bacillus WCHB1-69_norank has the function of producing electricity from auxiliary electrically active bacteria,and has been found enriched in large quantities on the anode surface for the first time,and the content is positively correlated with the power production capacity of the reactor.The analysis of the archaea community of in the electrodes of ITO anode MFC shows that the haloarchaea has the highest relative abundance content in the anode(40.6%),while in the cathode,the total amount of methane producing bacteria is the highest,accounting for about90%or more.The haloarchaea in the anode can promote the transmission of protons and accelerate the process of producing electricity,while most archaea are associated with methane production,which robs the substrates of electrically active microorganisms and protons of the system in the metabolic process,thus reducing the efficiency of electricity production.High-throughput sequencing results also show that the genus with the highest content in the anodes of the MFCs for alkali treatment of ITO anode and flexible graphite plate anode is the Geobacter of the Proteobacteria phylum,which presents different distributions in different areas of the anode.ITO material,after simple acid or alkali treatment,could be used as the anode to build flat anode MFC,with much higher power density than that of the carbon brush anode.Modified ITO anode and graphite plate anode can carry out in situ dynamic observation of the microbial and DNA analysis,which is an ideal material for the study of power production mechanism.As the low cost and easy to get materials,they have extensive practical application prospects.