Study On Advanced Treatment Of Landfill Leachate From Waste Transfer Station By α-MnO₂/PMS System

As a kind of high-concentration organic wastewater,the leachate from the refuse transfer station will have a serious impact on the environment if it is discharged into the environment improperly.Due to the unique characteristics of water quality and quantity of the leachate from the transfer station,there is no efficient,mature and economical treatment process for engineering practice at present.Although the traditional biological treatment can remove most of the organic matters,it has no good removal effect on the refractory organic matters such as humic acid and fulvic acid in the leachate from the transfer station,which makes it difficult for the effluent to meet the standards.Further advanced treatment is needed.In view of the problems of high treatment cost,complex operation and maintenance,and difficulty in practical engineering application,it is of far-reaching significance to develop new landfill leachate advanced treatment technology.Advanced oxidation technology based on sulfate radical has the advantages of high efficiency,green and stability,which has attracted more and more attention in the field of refractory organic wastewater treatment,and has a good application prospect.At present,however,the research on advanced persulfate oxidation technology mainly focuses on the treatment of simulated wastewater in laboratory,but seldom on the treatment of landfill leachate,so it is of great practical significance to study the advanced treatment of landfill leachate by advanced persulfate oxidation technology,which is helpful to develop a new advanced leachate treatment technology with high efficiency and easy practical engineering application.In this paper,the effluent of biochemical treatment of landfill leachate in advanced treatment transfer station withα-MnO₂/PMS persulfate system was constructed,and the effect and influencing factors of advanced treatment of leachate by this reaction system were investigated.On this basis,the changes of physicochemical properties of catalystα-MnO₂ before and after use and the removal efficiency of organic matter by oxidation and adsorption of catalystα-MnO₂ were explored,and the mechanism of advanced treatment of leachate biochemical treatment byα-MnO₂/PMS system was explored.The main conclusions of this paper are as follows:（1）According to the experiment,the optimal conditions of advanced treatment of leachate biochemical treatment effluent byα-MnO₂/PMS persulfate system are as follows:pH=7,stirring speed 180 rpm,reaction time 3 h,PMS dosage:PMS:19CODcr0=1.25:1（weight ratio）,andα-MnO₂ dosage:α-MnO₂:PMS=0.75:1（molar ratio）.Under the optimal working conditions,the removal rates of CODcr and TOC are 54.2%and 38.7%,respectively,the reverse utilization rate of PMS is 90.5%,and the CODcr concentration of effluent reaches the Class C of emission standard specified in the《Water Quality Standard for Sewage Discharge into Urban Sewers》（GB/T31962-2015）.（2）The effects of PMS:19CODcr0（weight ratio）,α-MnO₂:PMS（molar ratio）,reaction time and pH on the organic treatment efficiency ofα-MnO₂/PMS persulfate reaction system are in the order of PMS:19CODcr0（weight ratio）>α-MnO₂:PMS（molar ratio）>reaction time>pH.（3）After the catalystα-MnO₂ was reused for 4 times,its physical and chemical properties remained stable,and its activation performance for PMS remained good.The removal effect of organic compounds in leachate byα-MnO₂/PMS persulfate reaction system also remained stable.（4）Most of the organic matter in the effluent of landfill leachate biochemical treatment is fulvic acid refractory organic matter;Theα-MnO₂/PMS advanced oxidation system has a good oxidation effect on fulvic acid.Under the experimental conditions:the concentration of fulvic acid is 100 mg/L,the concentration of PMS is 10 m M,and the dosage ofα-MnO₂ isα-MnO₂:PMS=0.75:1（molar ratio）,the removal rate and mineralization rate of fulvic acid can reach 85%.（5）Common anions Cl^-,CO₃^2-,NO₃^-in leachate will reduce the treatment effect of organic matter byα-MnO₂/PMS system,but will increase the consumption rate of PMS and the final utilization rate of PMS.（6）Organic nitrogen and NH₄⁺-N in leachate can be oxidized to NO₃^--N by SO₄·^-.（7）The free radicals that degrade organic matter in the reaction system are SO₄·^-and·OH,and SO₄·^-plays a major role.The mechanism of activation of PMS byα-MnO₂ is discussed as follows:in the catalytic process,Mn（Ⅳ）first reacts with PMS to form Mn（Ⅲ）,and then reacts with PMS to form Mn（Ⅳ）and SO₄·^-,and Mn（Ⅲ）plays a decisive role in the catalytic process.