Characteristics Of Methane Anaerobic Oxidation Coupled To Electron Acceptors Reduction In The Aged Refuse

The mainly environmental pollution from landfill are landfill gas and leachate. Landfill gas CH4 is not only the important greenhouse gas, but also being used as energy. Biological cutting-down and control is the most economic-effective way to solve the problem of CH4 which could not be utilized as energy. Because the technology of leachate recharging and spray irrigation is one of the economic-effective and relatively simple ways to treat leachate, some researchers believe that they can effectively reduce leachate capacity and improve the leachate effluent water quality. According to the latest reports for methane anaerobic oxidation(AOM), SO42-, NO3- and Fe(III) can be used as electron acceptor coupled to AOM to remove the CH4. On the other hand, the aged refuses can be utilized as the functional material for wastewater treatment or cover medium. Furthermore, the law pre-treated leachate is rich in concentration of SO42- and Fe(III). That recirculaing leachate into aged refuse is a potential way that not only can cut down CH4 emission, but also remove the pollutants of the leachate in situ and simultaneously.Therefore, the work took the aged refuse landfilling more than 10 a as a medium. Firstly, it investigated the effects of different forms, concentration of iron and the coexistence with NO3- on AOM. Secondly, the research observed the feasibility of Fe(III) reduction coupled to AOM in the aged refuse by static batch type experiments. Finally, the paper studied the efficiency of AOM coupled to Fe(III) and NO3- reduction and the effects of coexistence of electron acceptors on coupling reaction by operating stimulated reactors. The reactors were set as landfill cover anoxic/anaerobic area and recirculated leachate which contains high concentration of SO42- and Fe(III). The main results were as follows:(1) In the anaerobic condition of the initial CH4 was 76.34 μ mol·g-1 dry refuse, KNO3, Fe3O4 and Fe Cl3 addition stimulated C H4 removal. The amount of CH4 removal was affected by the concentration of Fe3O4 or Fe Cl3. Adding 0.26 μ mol·g-1 Fe3O4 or 1.78 μmol·g-1 Fe Cl3 improved CH4 removal better. Fe3O4/Fe Cl3 and KNO3 being added together took antagonism effect on CH4 removal. However, NO3- had advantages of Fe(III) as for C H4 removal when the concentration of Fe(III) was low in the aged refuse. The production of CO2 had relationship with C H4 removal, but CH4 conversion process was not just the only one resource that generates CO2.(2) Apparently, occurrence of easily reducible materials, namely ferric iron and/or nitrate resulted in CH4 removal which included decreasing CH4 production and stimulating CH4 oxidation significantly(p<0.05). The inhibitory effects of various electron acceptor on CH4 production were in the order of KNO3+Fe Cl3>Fe Cl3>KNO3. AOM produced by Fe(III), NO3- and SO42- occurred in aged refuse. In the process of Fe(III) producing AOM, CH4 would stimulated the bioavailability Fe(III) reduced to Fe(II), and also promoted carbonated Fe(II) formation. Whereas, the coexistence of NO3- and Fe(III) took antagonism effect on CH4 removal and bioavailability Fe(III) conversion. Moreover, compared with adding NO3-/CH4 or Fe Cl3/CH4, the coexistence of CH4, NO3- and Fe(III) and their interactions would inhibit the formation of carbonated Fe(II).(3) The stimulated reactor running results showed that leachate recirculation could significantly reduce the concentration of NH4+-N and COD. Previous studies have reported AOM coupled to Fe(III) reduction occurred at low concentration of NO3- and SO42-. In our study, with addition of external Fe(III), NO3-, SO42- and Fe(III) can significantly promote CH4 removal(p<0.05) in the aged refuse. AOM was mainly dependent on NO3- and SO42- reduction at high concentration of NO3- and SO42-. However, AOM was mainly dependent on SO42-reduction under the low concentration of NO3- but high concentration of SO42-. Fe(III) driven AOM began to discover at low concentration of NO3- and SO42-. The kinetics fitting equations indicated that degradation of CH4 and generation of N2 and CO2 respectively correspond to zero-order kinetics. The kinetics reaction equation of degradation of CH4 for control group that adding without electron acceptor and treatment groups that adding with Fe C l3 or NO3- are C=-0.40 t +11.89, C=-0.72 t +13.18 and C=-0.83 t +12.39.