Experimental Investigation On Power Production And Waste Water Treatment Of Constructed Microbial Fuel Cell

The constructed wetland-microbial fuel cell(CW-MFC)is a new device which combines the the microbial fuel cell andartificial wetland to obtain the electric energy by anaerobic oxidation of the anode organic matter.The low sewage treatment effect and low electricity generation ability of CW-MFC limited its practical application.How to improve the output power of MFC and the degradation efficiency of pollutants is a focus of the current technology research.In this thesis,a CW-MFC was constructed for the purpose of enhancing electricity generation and promoting wastewater treatment.The artificial wastewater was employed as the pollutant.The synchronous purification effects and electricity generation performance which were resulted from wetland plants,electrode spacing,electrode thickness,ammonia nitrogen concentration and COD concentration were systhematically studied.The main contents and conclusions are as follows:The CW-MFC system was built on the foundation of MFC.Columnar activated carbon/carbon felt and columnar activated carbon/carbon felt/ copper grid were chosen as the anode and cathode of the battery,which constituted a single room CW-MFC composite system.In this study,we selected four kinds of wetland plants,iris,bambusa multiplex,dracaena sanderiana and scindapsus aureus to study the effect of plant species on the performance of CW-MFC.The plantation of wetland plants can increase the O2 content around the plant root,avoid the cathode exposure to the gas-water interface,improve the battery power density,reduce the internal resistance and improve the battery performance.The maximum output power(7.89 W/m3)of CW-MFC in these four kinds of wetland plants is iris-based cells.In addition,scindapsus aureus cell shows the best pollutant removal capacity(93% in removal rate of COD and 90% in ammonia nitrogen).To obtain the best power generation and pollutant removal efficiency,the effect of structure parameters of electrodes i.e.,electrode spacing and thickness,were studied.The electrode spacings that we chose were 10,20 and 30 cm,and the electrode thickness was 1,3,5 and 10 mm,respectively.Further,the polarization curves,internal resistance,output voltage and power value of the cells were obtained under different electrode spacing and electrode thicknes s conditions.The results showed that when the spacing is 10 mm,the output voltage can reach to 500 mv.The carbon felt showed the best power generation performance when the thickness is 3mm.This is because that too thin thickness would hinder the adhesion of electricity generation,and too thick electrode would repress the process of charge output.In addition,the electrode thickness has little effect on COD removal rate.The effects of water quality parameters on the performance of the cells were investigated by using ammonia concentrations of 1,10,20 and 30 mg / L and COD concentrations of 100,200,300 and 400 mg / L,respectively.Research shows low concentration of NH3-N is conducive to the electricity generation performance of CW-MFC.This is because that high concentration NH3-N will reduce microbial activity,thereby inhibiting the electricity g eneration of CW-MFC.Under the condition of 10 mg/ L ammonia concentration,a maximum power density of 13.59 W/m3 was observised.The higher the inlet NH3-N concentration was,the smaller removal rate could be achieved.In addition,the COD removal rate was negatively correlated with the inlet NH3-N concentration.The optimized power generation performance was obtained when the concentration of COD was 200 mg/L.