Advanced Treatment Of Landfill Leachate Based On Biochemical Coupling Catalytic Ozonation Technology

With the development of society,people’s living standards are improving day by day,and the disposal of a large number of garbage has followed.How to efficiently dispose of waste has always been one of the important issues.The commonly used waste disposal methods include sanitary landfill,composting and incineration.According to China’s national conditions,sanitary landfill is still the primary choice in most regions.In the process of landfill,landfill leach will be continuously produced due to the degradation of garbage itself or the action of rainwater.If it cannot be treated timely and reasonably,it will not only cause serious environmental pollution problems,but also harm people’s health,and thus produce a series of social problems.Therefore,this study conducted deep treatment of landfill leachate from Jiangcungou landfill leachate treatment plant at Xi’an based on biochemical coupled catalytic ozonation technology.The main research results are as follows:（1）In order to treat the high concentration landfill leachate,direct ozonation pretreatment and catalytic ozonation post-treatment coupled with anaerobic baffled membrane bioreactor（ABMBR）system was proposed in this study.After a series of treatments,the total removal efficiencies of COD and ammonia nitrogen were 91.2%and 99.4%,respectively.The chroma was remarkably decreased from 1250 times to 40times.In addition,Proteobacteria,Chloroflexi,Bacteroidetes and Brevundimonas in ABMBR could participate in the degradation of organic matter.Electron paramagnetic resonance（EPR）analysis indicated that the hydroxyl radicals were the main reactive oxygen species during the direct ozonation process,while the superoxide radicals played an important role in the catalytic ozonation process.（2）In order to optimize the structure of the landfill leachate treatment system,this experiment adopts the coupling process combining the activated sludge method and catalytic ozonation technology to treat the landfill leachate,including the activated sludge method pretreatment and catalytic ozonation combined with baffled membrane bioreactor（MBR）system.The COD,colority,UV₂₅₄,ammonia nitrogen,3D fluorescence peak value and fluorescence regional integration（FRI）of landfill leachate were all reduced.Ultimately,the maximum removal efficiencies of COD,ammonia nitrogen and phosphate were 98.46%,99.92%,and 79.71%,respectively.The heavy metal contents met the emission standards after treatment with this strategy.The deep removal of pollutants in landfill leachate could be attributed to the synergistic reaction of bacteria in activated sludge and catalyst in ozonation:（a）The bacteria found in sludge all played different roles,Proteobacteria and Bacteroidetes accounted for the most,they could degrade organisms and even refractory organic matters.Though the number of Thauera,Acinetobacter,Nitrospira and Nitrosomonas were small,they played an important role on denitrification.（b）During catalytic ozonation,the hydroxyl radical（·OH）produced by ozone would combine with oxygen to generate hydrogen peroxide radical（·OOH）during the reaction,while unpaired electrons were trapped by surface adsorbed oxygen on the catalysts to produce superoxide radical（·O₂^-）.In addition,the active metal components,such as Ce⁴⁺/Ce³⁺redox pair,Mn²⁺,Mn³⁺and Mn⁴⁺on the catalyst surface were able to transform synergistically,which was able to maintain the catalyst activity and realize the stable removal of contaminants.（3）In order to further improve the treatment efficiency of the system and reduce the complexity and cost of operation,the combination of activated sludge treatment method and catalytic ozonation technology was further simplified in this study,retaining only one anaerobic and aerobic alternating operation biochemical reactor and one catalytic ozonation reactor.Through continuously screening parameters,under optimal conditions,NH₄⁺-N descended from 1180.72 mg/L to 9.77 mg/L with the removal rate of 99.17%,UV₂₅₄declined from 7.2 to 1.98,colority reduced from 400times to 40 times,and the peak and region integration of 3D fluorescence also reduced significantly within 14 days.Target genes of AOB-amo A,nxr A,nap A,nir S and nos Z analysis indicated that different bacteria played a key role on nitrogen removal.Among,Halomonas,Pseudomonas,Paracoccus,Melaminivora and Luteimonas were in progress of denitrification.Therefore,the coupled process of activated sludge treatment and catalytic ozonation could realize the nitrogen removal effectively and deeply from landfill leachate.