Screening Of Efficient Electricigens And Their Application Research In Microbial Fuel Cell

To enrich the sludge collected from the aeration tan in Datianwan Sewage Treatment Plant in Jishou City, Hunan Province, a reaction equipment of microbial fuel cell (MFC) was designed and fabricated by ourself. The electricigens enriched by culture methods were isolated and purified and the electrochemical activity of the isolates were tested by cyclic voltammetry curve method. The biodiversity of the bacterial stains with electrogenic activity was studied by using the phylogenetic analysis based on16S rRNA gene sequences. The electricity generation characteristics and the operating results in treatment on domestic wastewater of MFC using the selected bacterial strain with high electrochemical activity as electricigens. The goal of this study was to screen a batch of electricigens, understand their phylogenetic diversity and explore the application potentiality of electricigens in electricity generation and treatment on domestic wastewater of MFC. The results would provide a theoretical basis and experimental guidance of how to develop and utilize this kind of microbial resources.To assemble the reaction equipment of MFC, suitable cathode,anode and proton exchange membrane(PEM) were selected and monitoring facilities were equipped.The sludge collected from the aeration tan were sealed and treated in labouratory to prepare an anolyte. The anolyte was added into the MFC reactor to enrich electricigens. The electricigens enriched by culture methods were separated and purified and the electrochemical activity of the separated stains were tested by cyclic voltammetry curve method. Results show that52kinds of electricigens were obtained, while37kinds of electricigens have electrochemical activity and5kinds of electricigens [F007(KJ846489), F010(KJ846473), F017(KJ846476), F026(KJ846478)and F051(KJ846507)] have high electrochemical activity.Results based on the phylogenetic analysis of16S rRNA gene sequences show that the37kinds of electricigens with electrochemical activity belong to15genus (Pseudomonas, Burkholderia, Luteibacter, Dyella, Rhodobacter, Haematobacter, Klebsiella, Caulobacter, Brevundimonas, Achromobacter, Paludibacterium, Myroides, Chryseobacterium, Sphingobacterium, Microbacterium) in11families (Pseudomonadaceae, Burkholderiaceae, Xanthomonadaceae, Rhodobacteraceae, Enterobacteriaceae, Caulobacteraceae, Alcaligenaceae, Neisseriaceae, Flavobacteriaceae, Sphingobacteriaceae, Microbacteriaceae) in3phylogenetic groups (phylum)(Proteobacteria, Bacteroidetes/Chlorobi group, Actinobacteria). Among them, bacterial strains which belong to Proteobacteria department are in a dominant position (32strains,86.5%), followed by strains of Bacteroidetes/Chlorobi group (3strains,8.1%) and Actinobacteria (2strains,5.4%). Compared the selected electricigens with the known efficient electricigens, we found that the dominant bacterial strains such as members of Rhodofoferax ferrireducens, Pseudomonas aeruginosa and Geobacter sulfurreducens, were of the same phylogenetic group (phylum Proteobacteria), while14bacterial strains [F001(KJ846471), F003(KJ846472), F010(KJ846473), F011(KJ846474), F013(KJ846475), F017(KJ846476), F021(KJ846477), F026(KJ846478), F027(KJ846479), F029(KJ846480), F032(KJ846481), F034(KJ846482), F037(KJ846483), F046(KJ846484)]belonged to dominant genus Pseudomonas of Pseudomonadaceae family. Other bacterial strains (F014(KJ846493), F018(KJ846494), F025(KJ846495), F031(KJ846496)) were rarely reported.Comparative analysis indicated that strains F010(KJ846473), F017(KJ846476) and F026(KJ846478) not only have a fine electrochemical activity, but also belong to the dominant genus. According to the experimental results of electricity generation of the three electricigens, F026(KJ846478) was selected as the electricigen to optimize the electricity generation of MFC. The results showed that using soluble starch as substrate, at35℃and neutral alkaline environment, the electricity generation properties of MFC was the best. Under optimal conditions, the voltage of the MFC reached up to500mV and the power density was more than2W/m3.Electricity generation using MFC with F026(KJ846478) as electricigen during domestic wastewater treatment were studied. The change of COD concentration and removal rate with MFC running time, the impact of COD concentration on substrate degradation process and stable voltage achievement were investigated.Results showed that substrate concentration influenced greatly the substrate degradation process and the stable voltage achievement.When COD concentration of domestic wastewater was200mg/L,pH was7.0, experimental temperature was30℃, the stable voltage of324mV were obtained after running4d and kept up for2.5d.The COD removal rate was more than90%after the domestic wastewater treated by MFC for6d with a power density of220mW/m3.