Treatment Of The Aging Landfill Leachate Using Membrane-less Air Cathode Single-chamber Microbial Fuel Cells

In this paper, 5 microbial fuel cells with membrane-less air cathode single-chamber were built. Effect of volume fraction of aging landfill leachate and electrode spacing on the electricity production, pollutant’s removal and mechanism of MFC(Microbial Fuel Cell) were researched.With the volume fraction of 20%, 40%, 60%, 80% and 100% of the aging landfill leachate as the substrate, the 5 membrane-less air cathode single-chamber microbial fuel cells, which called 1#, 2#, 3#, 4#, 5#, were built and run as the electrode spacing of MFC was 2 cm. The aging landfill leachate on the one hand can provide organic matters for microorganisms, on the other hand, there are inhibitory effects on microorganisms. Under the synergy of these two functions, the stable period of microbial fuel cells became longer with the increase of volume fraction of landfill leachate. This can explain that 5# MFC had the longest stable period. Increasing volume fraction, the output voltage and the power density would increase and the internal resistance would reduce for 1#MFC and 2# MFC. Thus, the output voltage of 2# MFC was higher than that of 1# MFC. For the 2 #, 3#, 4# MFC, the output voltage and the power density would reduce and internal resistance would increase as the volume fractions increased. When the volume fraction increased to 100%, the concentration of organic matter reached the maximum. And so, the output voltage of 5# MFC was higher than that of 4# MFC. In the inhibition of the maximum state, the electrochemical reactions and migration of ions in solution would be affected due to the promoting the growth of microorganisms in the greatest degree. So, internal resistance of 5# MFC was lower than that of 4# MFC and power density of 5# MFC was higher than that of 4# MFC. COD removal of substrate in 1 #, 2 #, 3#, 4#, 5 #MFC showed the same trend. COD removal reduced after a small increase in first 1-2d. With increasing volume fraction, COD removal efficiencies increased for 1#, 2# MFC and decreased for 3#, 4#, 5# MFC. The coulomb efficiency decreased for 1#, 2# MFC and increased for 3#, 4#, 5# MFC with the increase of volume fraction.The aging landfill leachate with a volume fraction of 60% as substrate, 5 single-chamber membrane-less air cathode microbial fuel cells called 6#, 7#, 8#, 9# and 10# were built and operated with electrode spacing of 1cm, 2cm,3cm, 4cm and 5cm. The change of battery electrode spacing can affect the performance of the battery, removal of substrate pollutants in substrate. The output voltage of the battery mainly depended on the potential difference between the electrodes, has little effect with the change of electrode spacing. In the 5 microbial fuel cells, the internal resistance increased with the increase of electrode spacing when the electrode spacing was in the range of 1-3cm. While the spacing was larger than 3cm, the internal resistance decreased as the electrode spacing increased. When the spacing was 1cm, power density of 6# MFC was larger than that of 7# MFC. The power density decreases with electrode spacing increased as the electrode spacing was in the range of 2-4cm. When the electrode spacing was 5cm, power density of 10# MFC was higher than that of 9# MFC. COD removal rate of substrate was the largest as the electrode spacing was 2cm. When the electrode spacing was 1cm, COD removal rate of 6# MFC was less than that of 7# MFC. COD removal rates of 8#, 9#, 10# MFC were less than that of 7# MFC when the electrode spacing was larger than 2cm. Coulomb efficiencies of 5 microbial fuel cells were 35.63%, 27.65%, 35.43%, 14.86%, 14.94%, respectively.In the above experiments, Nitrogen removal in substrate was mainly removed by ammonia nitrogen degradation, ammonia nitrogen is mainly converted into gas discharge in the first part of experiment but ammonia removal is mainly converted to gas and a small portion is converted to nitrate nitrogen in the second part of experiment. The microbial fuel cells can slightly improve biodegradability of substrate. In the first part of experiment, the p H value of substrate was stable after it increased at first, and conductivity was stable after the first decreased. In the second part of experiment, the p H value of substrate was stable after it increased at first, and conductivity decreased.