Study On Component Characteristics And Treating Of Advanced Oxidation With Microwave For Landfill Leachate

With the development of society and living standards,the amount of wastes increases dayby day.Landfill leachate has become an important source of refractory organic wastewater,which threats the security of water source.So treating technique on landfill leachate has beenvery important in field of environmental engineering.At present,main researches on landfill leachate focuses on the treatment methods ofbiological and physico-chemical,but these methods is less effective to landfill leachatebecause of complex composition and high content of refractory organic matter.Overall,thestudy about landfill leachate is still in primary stage.The component and phase characteristicsand the treatment mechanism of the leachate are all lack of analysis.What's more,there arenot effective methods to treat the landfill leachate in practice,so the study is still needed inmany aspects deeply.In this dissertation,leachate from the buried landfill in Jiangcun gou ofXi'an is studied on analysing the state of material and the structural characteristics ofparticulate in leachate.And then landfill leachate is treated by coagulation and advancedoxidation with microwave,and the mechanism is studied on the basis of micro-analysis.The conventional indicators and the composition characteristics of landfill leachate canreflect its pollution characteristics and impact the treatment effect of leachate in a large extent.At first,the conventional indicators and content of pollutants in landfill leachate aredetermined,and the micro-structure of organic phase of landfill leachate is analyzed by GCand GC-MS.Butyric acid,phenol,indol and polycyclic aromatic hydrocarbons are inferredin the solution phase of leachate by GC,and 53% of organic acids,18% of alcohol andphenols,and 7% of alkanes are detected in leachate by GC-MS.The colloidal structure oflandfill leachate is analyzed by determination ofξ-potential and the interfacial tension,whichprovide the basis to pretreatment by the coagulation and treatment by advanced oxidation.A large number of pollutants existence with particulate matter in landfill leachate,so thesize and content of particulates are analyzed.The characteristics of particulate is detected byDSC and FTIR before and after acidizing of leachate.The results showed that the particleslarger than 30μm are mostly flocculent and about 10μm particles are mostly granular and thesize of particles are not uniform.Five characteristic peaks appear in the spectra of DSC and the peaks are great,and the value of total enthalpy is greater.Three characteristic peaksappear in the spectra after acidification and the peaks are small,and the position of peak ismoved to the high temperature zone and the value of total enthalpy decreases.The original ismade from the skeleton of aromatic and condensation of aldehyde or ketone and unsaturatedcarbon-oxygen bond.Phenolic hydroxyl,carboxyl,methyl and amino can be inferred inorganic particles by FTIR.On the base of characteristics particulate and colloidal of leachate,the effect of thecoagulation is studied for the removal of pollutants in different phase.The effect of dosage ofAlCl₃ and PAM,pH,hydraulic conditions,and the settlement time is analyzed on the removalCOD,NH₃-N and turbidity of landfill leachate,and the optimum coagulation conditions aredetermined.At this time,the turbidity is reduced by 98.22%,and the removal rates of CODand NH₃-N is 31.55% and 22.79%.Advanced oxidation by microwave is use to treat landfill leachate on the basis of thesystematic analysis of various pollutants in leachate.With the help of orthogonal design andanalysis of gray relational theory,reasonable test conditions are determined:the initialconditions of pH=3,the volume of GAC is 10g/L,the weight of Fe(â…¡)is 333.2mg/L,thepower of microwave is 720w,the treating time of microwave is 30min,and the amount ofH₂O₂(30%)is 10ml/L.The different characteristics and the reasons of the removal rate ofCOD and NH₃-N with the changes of treating conditions was analyzed based on mechanismof microwave and catalytic oxidation.And the catalytic oxidation effect of microwave andH₂O₂ is analyzed.Various organic compounds and polycyclic aromatic of landfill leachatehave been degraded to CO₂ and H₂O or similar compounds after treatment and the content isreduced significantly.On the base of the microwave role,the degradation and transformation process of typicalorganic pollutants in landfill leachate,such as alkane,aromatic,aromatic amino compound,and heteroaromatic compound,are studied by the role of the·OH.The role of GAC in thereaction is discussed.Kinetics of advanced oxidation with microwave is researched to get thekinetics model:-dC/dt=kC^2.08(C′)^0.72.