Treatment Of Biochemical Tail Water In Landfill Leachate By Magnetic Coagulation/Catalytic Oxidation

Landfill leachate is a type of wastewater that highly polluted and rich in organics.It is difficult to meet the standard emission standards by using the cu_crent conventional biochemical treatment methods,and to perform advanced treatment of biochemical tail water according the latest revision?Standard for pollution control of municipal solid waste landfills??GB16889-2008?.Leachate biotreated tailwater from MaiYuan landfill being studied on the target,establishment of enhanced coagulation,catalytic oxidation,and coagulation-catalytic oxidation coupling process to treat leachate.Single factor experiments were used to optimize the treatment process,and important factors were selected.Response surface methodology was used to establish a mathematical model for the degradation of leachate by important influencing factors.Based on the experimental data,the interaction between various factors in the model was analyzed and the response surface methodology was used to determine the best operating parameters for each process.3DEEM,FTIR,GC-MS and other microscopic characterization methods were used to comprehensively analyze the content,types and functional groups of organic pollutants in water.In this paper,the following conclusions were drawn from the deep treatment of leachate by coagulation and oxidation.Flocculation treatment leachate optimization experiment parameters,the increase of PAC and pH,the removal rate of COD_crr and UV₂₅₄54 in the coagulation process showed a trend of first increase and then decrease.When the PAC dosage was 1 g/L,the highest COD_crr removal rate was 40.2%,and the UV₂₅₄54 removal rate also reached the maximum,and a better color removal,from the optimization experimental parameters on leachate.COD_cr,color removal effect showed a trend of first increase and then decrease,it strengthens the flocculation of polyaluminum chloride through Fe₃O₄ magnetic material.When Fe₃O₄ dosage was 1.5 g/L,the COD_crr removal rate of leachate was 59.6%,which was higher than the effect of adding flocculant alone,indicating that Fe₃O₄ played a heterogeneous nucleation function and provided for the formation,aggregation,and sedimentation.The results show that the treatment effect of Na₂S₂O₈/H₂O₂ coupling system is obviously better than that of adding one oxidant or adding two oxidants in succession.Therefore,the dual oxidant system is effective and feasible on oxidation treatment of landfill leachate.Optimizing the leachate treatment process parameters by the response surface method has a good technical guidance value and is optimized within the selected range to obtain the optimal treatment effect.The optimum process parameters for fe_crous catalysis are:COD_crr removal rate of leachate is reached 70%under the condition that the fe_crous dosing amount is 2 g/L,the amount of sodium persulfate is 1.75 g/L,and the amount of hydrogen peroxide is 3 mL/L.The optimum process parameters for zero-valent iron catalysis are as follows:ZVI concentration31.3 mM,pH 4.4,andS₂O₈^2-/1 2COD₀1.14 reaction conditions,the best effect of COD_crr removal rate is 72%.Analysis of variance showed that three important factors affecting the interaction of leachate COD_crr removal between two two significant.When both oxidation and coagulation were combined,COD_crr removal efficiency was 21%and oxidation was 42%.Comparing the two treatment methods,it was found that COD_crr removal efficiency of landfill leachate after precoagulation oxidation was slightly higher than COD_crr removal rate of landfill leachate after preoxidation followed by coagulation.When the optimum dosage of flocculant was added at 1 g/L,the efficiency of the former was 14.3%higher than that of the latter.In the combined process of coagulation/oxidation stabilization of landfill leachate,the COD_crr removal rate averaged over 70%and the highest reached 85.6%,indicating that the oxidative coagulation achieved a good treatment effect.The characteristics of water samples before and after coagulation and oxidation treatment were characterized by 3DEEM and other methods.The results showed that the degree of dissolved organic matter?DOM?pollution in the treated water samples was reduced and the humic acids were largely degraded into small-molecular-weight fulvic acids;The condensation degree and aromaticity of organic molecules in water samples decreased The determination of the organic functional groups and structures in the water samples before and after treatment by FTIR showed that the main functional groups and structures of the water samples had some changes before and after treatment.