Study On Landfill Leachate Treatment By Three Dimensional Electrode Method With Activated Carbon Filler

Landfill leachate,as a kind of high concentration organic wastewater,has the characteristics of great variation of water quality,complex composition and difficult degradation.The direct discharge of landfill leachate without treatment or improper treatment will cause serious impact on the environment and human life.As an efficient and clean treatment technology,three-dimensional electrode method has the advantages of simple equipment,large capacity and no secondary pollution,etc.,and has been widely used in the treatment of high concentration and difficult degradation organic wastewater.At present,the research on 3D electrode method mainly focuses on the selection and optimization of anode materials and particle electrodes.There are many kinds of particle electrode materials,among which activated carbon is the most widely used.However,the contact of activated carbon with each other will produce a lot of short circuit current,which will reduce the degradation effect and increase the energy consumption.Therefore,many scholars improve the current utilization efficiency of the three-dimensional electrode system by filling insulating particles.In this study,silicone resin coated activated carbon was used to prepare insulating particles,and activated carbon three-dimensional electrode system was constructed to treat the effluent from the upflow anaerobic sludge bed（UASB）of the leachate treatment system of waste incineration plant.The removal effect of COD and ammonia nitrogen in wastewater,energy consumption and current efficiency before and after the addition of activated carbon were investigated.The main conclusions are as follows:（1）The removal effect of COD and ammonia nitrogen in the leachate by three dimensional electrode system before and after the addition of coated activated carbon was studied respectively.The results show that when the current density is 60m A/cm²,the Na₂SO₄dosage is 0.4g/L,the active carbon filling mass concentration is 800g/L,the initial pH is 5,the distance between the plates is 6cm,the COD removal rate of the pure activated carbon 3D electrode system is 68.5%,and the ammonia nitrogen removal rate is 99%after 6h of electrolysis.When the filling ratio of coated activated carbon to activated carbon is 1:2,the COD removal rate is 76.6%and the ammonia nitrogen removal rate is 90.3%after 6h of electrolysis under the same conditions.（2）By comparing the energy consumption and current efficiency in the treatment process of the two systems,it can be seen that the total energy consumption decreased from1792.9k·Wh/（kg COD）to 956.8k W·h/（kg COD）after 6h electrolysis under the optimized conditions after the addition of coated particles,which significantly reduced the energy consumption and increased the current efficiency.（3）The degradation mechanism of COD and NH₃-N in the coated activated carbon three-dimensional electrode system is roughly the same,which is mainly the direct and indirect oxidation in the electrochemical reaction.In the early stage of the reaction,direct oxidation is the main method for COD degradation,and indirect oxidation is the dominant method for COD degradation.Because of the high concentration of Cl^-in the leachate,the degradation of ammonia nitrogen is dominated by indirect oxidation.（4）The conversion of ammonia nitrogen under different current density,electrolyte concentration,initial pH and plate spacing was studied.Under the action of strong oxidizing group and active chlorine,ammonia nitrogen was converted into nitrogen,nitrate nitrogen and chloramine,which was removed.Under different conditions,there is little difference in the conversion form of ammonia nitrogen after electrolysis for 6h,most of which is converted into nitrogen,and a few into nitrate nitrogen.A small amount of chloramine is accumulated in the electrolysis process.Among them,the main factors that affect the conversion form of ammonia nitrogen are the acidity and alkalinity of the solution,and the proportion of ammonia nitrogen converted to nitrate nitrogen increases under alkaline conditions.