| China's municipal waste has a high moisture content.A large amount of leachate will be generated during landfill,incineration or composting.Leachate is a high concentration of organic wastewater containing a variety of toxic and harmful substances such as dissolved organic matter,inorganic salt components,heavy metals,and polycyclic aromatic hydrocarbons that have“triple”effects.How to deal with leachate economically and efficiently is a major challenge for the harmless treatment of municipal waste.The semi-aerobic aged refuse bioreactor for treating leachate is a waste treatment technology.This technology has the advantages of rapid degradation of leachate organics and efficient denitrification,but it generates N2O during nitrification and denitrification.Biochar has aromatized structure,large specific surface area and porosity,it is commonly used in greenhouse gas emission reduction,sewage purification and soil remediation.Biochar can affect the transformation of soil nitrogen and reduce N2O emissions,but the application of biochar in leachate treatment by semi-aerobic aged refuse bioreactor has not been reported.Therefore,the experiment set up 4 semi-aerobic aged refuse bioreactors to treat leachate,and the amount of biochar added was 1#:0%,2#:0.25%,3#:1%,4#:3%.By analyzing the indicators of carbon content in leachate effluent,UV-Vis spectroscopy,and three-dimensional fluorescence spectroscopy,the effect of biochar on leachate organic pollutant removal and conversion was explored.At the same time,combined with the nitrogen pollutant of leachate and N2O,N2 emission flux of semi-aerobic aged refuse bioreactor,the effect of biochar on the denitrification efficiency of semi-aerobic aged refuse bioreactor,in order to provide certain theoretical guidance and reference for the application of biochar in the treatment of leachate by semi-aerobic aged refuse bioreactors.The experiment was conducted for a total of 98 days,of which the domestication period was 28 days and the operation period was 70 days.After the domestication period,the CODCrr removal rate of the 4 semi-aerobic aged refuse bioreactor was stable at 88.18%,83.84%,93.87%and 96.02%.The UV25454 removal rate was stable at 87.14%,85.54%,93.60%and 94.98%.The CN removal rates were about 94.50%,93.65%,98.02%,and98.62%,respectively.It indicates that the domestication effect of semi-aerobic aged refuse bioreactors is better.During the operation period,the removal rate of CODCrr in the leachate from the four semi-aerobic aged refuse bioreactors was 1#:77.71%85.39%,2#:82.94%89.85%,3#:83.77%92.24%,and 4#:84.48%94.60%;The removal rates of UV25454 were 1#:67.22%87.94%,2#:72.77%88.14%,3#:76.18%92.39%,and 4#:81.7194.39%,the CN removal rates were 1#:64.39%87.61%,2#:72.42%88.46%,3#:83.68%92.33%,and 4#:87.4397.02%.The removal rates of the three indicators are all expressed as 1#<2#<3#<4#,it shows that the addition of biochar can increase the removal rate of carbon pollutants in leachate by semi-aerobic aged refuse bioreactor.The higher the biochar addition,the better the organic removal effect is.The higher the amount of biochar added,the better the removal of organics.The results of UV-Vis showed that long-chain organics and macromolecule organics are degraded into short-chain organic and small-molecule organics after the leachate is treated with semi-aerobic aged refuse bioreactor.The results of 3D EEM show ed that after the leachate was treated with mineralized waste,the results of three-dimensional fluorescence spectroscopy showed that after the leachate was treated with semi-aerobic aged refuse bioreactor,the fulvic acid in the visible region was converted to fulvic acid in the ultraviolet region.During the operation period,the average removal rates of NH4+-N by 1#,2#,3#,and 4#were 97.69%,98.53%,98.71%,and 98.86%,and the average removal rates of TN were40.94%,39.11%,43.78%,and 44.61%.The trend of TN and NH4+-N removal was1#<2#<3#<4#,indicating that adding biochar could increase the removal of leachate NH4+-N and TN by semi-aerobic aged refuse bioreactor.The daily N2O emissions of 1#,2#,3#,and 4#were 31.455,27.349,26.790,and 23.678 mg,and the daily N2 emissions were409.622,411.130,415.210,and 419.876 mg,it shows that the addition of biochar can reduce the N2O emission,promote the conversion of nitrogen pollutants into N2,and improve the nitrogen removal effect of semi-aerobic aged refuse bioreactor. |
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