A Study On Treatment Of Mature Landfill Leachate By Coagulation And Electrolysis Process

Mature landfill leachate is a kind of high concentration organic wastewater produced during 5?10 years of landfilling that contains high concentrations of ammonia nitrogen.pollutants,and a certain amount of heavy metals.However,due to the poor biodegradability of the mature landfill leachate which most organic pollutants are bio-refractory organic,and the toxicity of high concentrations of ammonia and heavy metals,it is hard to treat the mature landfill leachate effectively with the traditional biological treatment.This may cause a lot pressure to the membrane treatment in the post-treatment.In this study,the mature landfill leachate which produced from the landfill was chosen as the research object and treated with the combined treatment of coagulation and electrolysis.The polysilicate aluminum ferrite?PSAF?was chosen as the coagulant to add into the mature landfill leachate for the coagulation treatment.And the orthogonal test method was used to determine the optimal the dosage of PSAF.The effluent of coagulation treatment was electrolyzed with Sn O₂electrode to further remove organic pollutants and ammonia remained in the landfill leachate.And the response surface method?RSM?was used to analyze the optimal electrolysis conditions and the significant factors affecting COD_Crremoval rate.Furthermore,GC-MS and 3D fluorescence spectroscopy were used to analyze the water quality.The main conclusions of the experiment are as follows:1.As PSAF was used as coagulant to pretreat late landfill leachate,the removal rates of COD_Cr,TOC and UV₂₅₄were 52%,62%and 42%respectively when the dosage of the dosage of PSAF was 5.1 g/L,the initial p H was 6,and the dosage of polyacrylamide was 2mg/L.The results of orthogonal test showed the level of the influencing factors to coagulation were the dosage of PSAF>initial p H>the dosage of polyacrylamide.2.As Sn O₂electrode was used to treat the coagulation effluent of landfill leachate for electrolysis,Considering the comprehensive removal performance of pollutants,the current density was 180 m A/cm²,the initial p H was 7,and the electrode gap was 1 cm,the COD_Crremoval rate reached to 89.3%after 4 hours of electrolytic treatment,means the COD_Crremoval rate of the landfill leachate in entire process was 95.4%,and the concentration of COD_Crremained in the effluent reduced to 160 mg/L.In this electrolysis condition,the ammonia nitrogen in leachate was completely removed within 3 hours,and the removal rate of TOC and UV₂₅₄after 4 hours of electrolytic treatment were 60%and 73%,respectively.As current density,initial p H value,electrode gap and reaction time were chosen as the control factors,and COD_Crremoval rate was chosen as response variable,response surface method?RSM?was used to analyze the experiment and reasonable fitting is obtained.3.The analysis results of GC-MS showed the organic pollutants in leachate were greatly reducd after the combined treatment,in which the macromolecular refractory organics were degraded into micromolecular organics.The results of three-dimensional fluorescence spectrum showed the fluorescent pollutants in leachate were greatly reduced after coagulation and electrolysis treatment,which Humic acids and fulvic acids were almost completely removed.By analyzed the evaluation of ammonia during the treatment process,due to the generation of active chlorine?HCl O/Cl O^-?with strong oxidization,most of the ammonia in the leachate was converted into nitrogen,and a small amount of ammonia was converted into nitrate nitrogen remained in the leachate.