Electricity Generation From Swine Wastewater In Microbial Fuel Cell, Microbial Community Analysis, And Isolation Of Electricigens

Microbial fuel cell (MFC) is a newly arising technology that could generate electricity from organic matters when degrading organic substance. The swine wastewater is a typical kind of high-concentrated organic wastewater. This paper discussed the effect of electrogenesis and water purification based on air cathode single chamber MFC model, researched the molecular phylogenetic diversity of bacteria of MFC anodic biofilm, and screened out the electriciy producing bacterial strains. The main conclusions of this work are made as follows:(1) The batch mode air cathode single chamber MFC were built successfully, which were inoculated on the anaerobic active marshy mud of swine wastewater, and had cathode of carbon paper loaded with platinum and anode of carbon fiber felt. The results revealed that the two MFC power output of 0.514 V and 0.527 V(20 d, 500Ωexternal resistance)steadily when it was on the basis of glucose substrate. If increasing the proportion of swine wastewater in substrate until it comes to 100 %, the internal resistances of the two MFC reached 169Ωand 178Ωand the maximal power density reached 208 mW/m² and 158 mW/m² respectively, mesured by steady-state discharge method. Water quality monitoring showed the average COD_cr removal efficiency of the two MFC is 85 % and 78 % and the average ammonia nitrogen removal efficiency was 52 %å'Œ45 % within a running cycle. What's more, the effect of removing the odor of the real wastewater was obvious.(2) The microbial community analysis based on PCR-DGGE method of anodic biofilm samples of MFC, including the start-ups (S), electricity producing stationary phase (RG), and real wastewater stationary phase (RS). The results indicated that the microbial community exist great difference in microbial diversity of anodic biofilm among different period samples. The microbial communities'similarity of S-RG S-RS and RG-RS is 70.1 %, 42.0 % and 50.6 %, respectively. There were high sequential similarities between microorganisms in anodic biofilm samples. They were Trichococcus sp., Thauera sp., Azoarcus sp., Azospirillum sp., Zobellella sp., Pseudomonas sp., Aeromonas sp., Thiobacillus sp., Desulfovibrio sp., Thiomonas sp. Besides, the microbial communities'similarity in swine wastewater elctricity producing stationary phase is 48.0 % between the MFC equipped with ethylenediamine modification anode and ferric trichloride modified anode.(3) The MFC electricity generating experiment inoculating with the isolated pure cultures and electrochemical test revealed that 4 isolated pure bacterial strains showed high electrochemical activity. Two of them maximum power output reached 0.34 V and 0.33 V (external resistance 1000Ω, glucose density 1 g/L, PBS 50 mM, pH 7.0), and maximum power density 505 mW/m² and 495 mW/m². The result of molecular identification demonstrated that the two isolated strains had high sequence similarity with Proteus vulgaris (99.9%) and Raoultella sp. (99.8%), respectively.