| Black-odorous freshwater sediment, 50 m M/L ferricyanide buffer solution, a double-chamber plexiglass reactor and proton exchange membrane(PEM) were used in this study for constructing a double-chamber microbial fuel cell(MFC). By changing theoperating condition in every cycle, the main contents in this study including: the investigation of the capacity for MFC to run and generate electricity, the analysis of the sediment remediation based on MFC, and further study of methane emission in the process of sediment remediation. Several conclusions were got as follows:(1) MFCs were training by sequencing batch type, with black-odorous freshwater sediment as the anode inoculum and 1 g/L glucose solution as the nutrient solution. MFCs successfully started after a run time of 720 h, and the maximum woltage could reach 0.767 V. After a successful start-up, MFC could maintain a higher level of voltage in a relatively long time(> 200 h) when sediment as the anode substrate.(2) Black-odorous freshwater sediment and 50 m M/L ferricyanide buffer solution were used in this study for constructing experiment system, treatment groups and the control group were set in every operation cycle. In the cycle of changing the external resistors, aerating in the cathode chamber and adding ferricyanide in the cathode chamber, the internal resistances of each MFC were 1300 Ω around. The maximum power density in this three cycles was appeared in the external resistance of 1500 Ω, the aeration time of 6 h and the ferricyanide concentration of 200 m M/L respectively, the corresponding maximum power densities were 4.94 m W·m-2、6.00 m W·m-2 and 6.45 m W·m-2. When Nacl was adding in the cathode chamber, the internal resistances of MFC changed significantly because of the changed solution conductivity. The constituent of anode substrate also impact the internal resistances of MFC. The internal resistance of the MFCs decreased with respect to Na Cl concentration order, the highest power density was 6.64 m W·m-2, it was measured at the Na Cl concentration of 200 m M/L and the corresponding internal resistance was 1140.4 Ω. When the volume ratio of sediment and water was 1:1, the internal resistance was 902.1 Ω and the maximum power density was 7.24 m W·m-2. The internal resistances of MFCs were large on the whole, the mainly reason was the existence of PEM increased the internal resistance, and as a mixture of mud and water, sediment had a larger resistance than aqueous solution.(3) The MFC systems constructed in this study could be used to repair sediment while generating electricity. The results showed that the anode biofilm greatly promoted the degradation of organic content in sediment. In five operation cycles, the highest removal rate of organic content were 7.83%、11.65%、10.15%、11.35% and 11.57% respectively, and they all achieved at the maximum power density of MFCs. In the same operation cycle, the removal rate of organic content increased as power density increased.(4) The anode biofilm had a certain effect on getting rid of phosphorus from sediment. When organic content in sediment as the main fuel source, the change of power density and the removal trend of ammonium nitrogen did not present an evident rule. Ammonium nitrogen in sediment can be removed as electron donor by biofilm oxidation. The anaerobic environment in anode chamber was conducive to the denitrification for nitrate removal. At the same time, nitrate in sediment was potential electronic competition body in anode chamber and as electron acceptor, enough electronic donor should be degraded by biofilm to provide electron to remove nitrate nitrogen.(5) The double-chamber MFC systems constructed in this study sped up the methane emission rate of sediment while repairing sediment and generating electricity. For treatment groups, CH4 showed a trend that the emission decreased as the power density increased. As substrates in anode chamber were sediment only, the generation of methane were also affected by mass and electronic transfer. When substrates in anode chamber were changed, the kinds and constitutions of organic content in substrates had a great influence on methane generation.(6) The double-chamber MFC systems constructed also affected CO2 and N2 O production and emission while repairing sediment and generating electricity. The production and emission trends of CO2 and N2 O were consistent in the same operation cycle, which presented a increased trend with the power density increased. The generation of CO2 was associated with organic matter degradation, the more organic content degraded, the more CO2 discharged correspondingly.. N2 O mainly came from denitrification. The anaerobic environment in anode chamber was conducive to the denitrification. |
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