| With the problem of energy crisis and environmental pollution getting more and more serious in recent years, researching and developing advanced waste water treatment process which can recycle the energy of waste water has became a significant aspect of sewage treatment area. Microbial Fuel Cell (MFC) is exactly the kind of new type biological treatment technology that can transform the organic matter of waste water into clean energy-electric energy. Currently, the study of MFC still remains in basic research stage that most of the research work focuses on the electrogenesis characteristics of anode of abiocathode MFC and treatment of organic matter. However, the much more environmentally friendly biocathode MFC is relatively less studied, and the waste water treatment which just emphasizes organic removal but neglects eutrophication causing element such as nitrogen and phosphorus is obviously unsatisfactory.In allusion to the problem that exists in the study of MFC at present, this study investigated two dual-chambered denitrification MFCs, explored and optimized the start-up process. With theoretical approach of electrochemistry and waste water treatment, the electrogenesis capacity and pollutant removal performance was studied, and the feasibility of denitrification of MFC was verified. On that basis, the influencing factors of electrogenesis capacity and pollutant removal performance of denitrification MFC were studied emphatically. The main conclusions are as follows:(1) Compared with the start-up method of continuous feeding followed by batch feeding, directly continuous feeding start-up method with optimized experimental condition made the start-up time reduce from45d to110h; the voltage of MFC increase from429mV to450mV, the removal loading of COD and NO-3-N increase from1.214kg/(m3NC·d),0.045kg/(m3NC·d) to1.672kg/(m3NC·d),0.085kg/(m3NC·d) respectively, when the external residence was set at50Ω.(2) When oxygen existed in influent of cathode, oxygen could serve as electron acceptor of MFC prior to nitrate, MFC could use abundant nitrate as electron acceptor to keep the increase of current density only if current density had increased to a certain extent that all the limited dissolved oxygen had been reduced to generate electricity. When influent COD concentration was200mg/L, the external resistance had little effect on COD removal loading and the cathode effluent concentration of NO-2-N that COD removal loading remained at about1.2kg/(m3NC·d) with the cathode effluent concentration of NO-2-N below0.05mg/L at any external resistance; but decreasing the external resistance which resulted in current increase could improve nitrogen removal performance that the NO-3-N removal loading reached to0.111kg/m3NC·d when the external resistance was set at5Q.(3) Within the temperature range of15℃～30℃, the anode performance barely changed while the maximal current density and power density which were generated with oxygen as electron acceptor decreased gradually as temperature rose. When the temperature was15℃and all the dissolved oxygen of cathode was used to generate electricity, the denitrifying bacterium could not use nitrate as electron acceptor to keep the increase of electricity because of low temperature. Within the temperature range of20℃～30℃, MFC had good electrogenesis capacity and pollutant removal performance which were the best at25℃.(4) When influent pH of anode and cathode were set at8.0and6.0, the limited current density and the maximal power density of MFC increased with the increase of influent COD and reached to maximal values:223.1A/m3NC,62.5W/m3NC respectively when the influent COD=450mg/L. The COD and NO-3-N removal loading increased with the increase of influent COD and reached to maximal values:2.653kg/(m3NC·d),0.545kg/(m3NC·d) respectively when the influent COD=450mg/L, but which were not significantly higher than that of influent COD=400mg/L.(5) When influent concentration of COD was300mg/L and cathode influent pH was set at6.0, the higher the pH was the more electricity MFC generated within the anode influent pH range of6.0～8.0. The maximal current density and power density of MFC reached to161.5A/m3NC,54.0W/m3NC at anode influent p11of8.0, which were two times as much as that of anode influent p11=6.0. The maximal COD removal loading was just1.870kg/(m3NC·d) when the anode influent p11was6.0but maintained at about2.1kg/(m3NC·d) with other p11values. NO-3-N removal loading increased with the increase of anode influent pH, and the maximal value was0.383kg/(m3NC·d).(6) When influent concentration of COD was300mg/L and anode influent pH was set at8.0, within cathode influent pH range of5.0-8.0, the limited current density and the maximal power density of MFC reached to maximal values:199.1A/m3NC,73.6W/m3NC respectively at cathode influent pH of6.0, and the maximal NO-3-N removal loading reached to maximal value:0.431kg/(m3NC·d) at cathode influent pH of6.5. When cathode influent pH was5.0the maximal cathode effluent concentration of N0-2-N was0.661mg/L, but mostly remained below0.05mg/L with other cathode influent pH value. |
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