Study On Treating Swine Wastewater By Continuous Flow Microbial Fuel Cell With Biological Cathodes

Microbial Fuel Cell(MFC) can directly transform the substrate into electric energy, and realize to converse biological energy into electrical energy, and the co nversion rate was up to 80%. At the same time, it also can treat the piggery wastewater with high concentration of organic nitrogen by means of nitrate nitrogen to receive electron. This paper studied the effect of producing electricity and the characteristics of substrate degradation through construct the continuous Denitrification Biological Cathode Dual Chamber MFC system, which was inoculated on the anode with granular sludge in the double chamber MFC running a long time, and on the cathode chamber with sludge of nitrification and denitrification from piggery wastewater treatment by SBBR reactor. Besides, the effect of the load resistor, C/N, and water flow rate and degree of agitation were investigated. At the end, the paper took the actual swine wastewater as substrate, and investigated the producing electricity efficiency and the effect on treatment of piggery wastewater.The experiment took simulated wastewater as the starting substrate which included glucose concentration of 3g/L and ammonium chloride concentration of 1.6g/L. So the influent COD is about 2000mg/L, NH3-N is about 420mg/L and p H is 8. The load resistance of MFC system is 75 ohms. With the continuous culture, the anode chamber can finish the exoelectrogenic bacteria directional enrichment and the startup process after 200 hours, and the cathode chamber can finish the denitrifying bacteria directional enrichment and startup process after 195 h. The operation of the MFC was stable when the output voltage was stable at about 473 m V, meanwhile the COD concentration in the anode chamber decreased from 2000mg/L to 395mg/L with the removal rate of 80.2%, NH3-N decreased from 422mg/L to 201mg/L with the removal rate of 52.4%. At this time, the cathode electrode potential remained at about 31 m V stably without the obvious change, the NO3-N concentration in cathode chamber decreased from 422mg/L to 47.5mg/L with the removal rate of 88.5%.Then the paper studied the apparent internal resistance of the MFC system with the ohmic polarization curves, and it showed that the apparent internal resistance of the MFC system is 4.6 ohms, with the open circuit voltage of 554.8 m V and the maximum output power density of 0.98W/m2, at the same time, the correlation coefficient is 0.9576.After the stable operation of the MFC, this paper analyzed the influence factors of the experiment, with the load resistance chosed in 550?、450?、350?、250?、150?、100?、70?、50?,and the result showed when the load resistance was in 70 ~350? the MFC had better performance. Then the water flow rate was chosed in 4ml/h, 6ml/h, 8m L/h and 10 m L/h, and the result showed when the influent flow rate was 6~8 ml/h, the MFC has better performance through a comprehensive review of the MFC system both the electricity production and substrate removal effect. The C/N rate were 10:1, 6.7:1, 5:1, 4:1 and 3.3:1, and the results showed that when C/N was 4:1~6.7:1, the MFC system has better performance. Through the anode chamber of MFC with and without mixing experiments, the electricity production and substrate degradation properties of MFC were studied in different degree of agitation. The results showed that the MFC system has a better performance with the power density of 0.385W/m2 and the coulombic efficiency of 4.48% under the conditions of stirring.The paper conducted another experiment with actual swine wastewater by optimizing conditions, it got the stable output voltage of 530 m V, the cathode electrode potential of 45 m V. Meanwhile, the removal rate of COD was 84.6% and the removal rate of NO3-N was 78.5%. The results showed that the MFC system still had a efficient electricity production and a better removal rate of substrate with actual swine wastewater and optimal conditions.