| Landfill leachate is a kind of high concentration organic wastewater with many components and difficult biodegradation in the process of landfill.Landfill leachate has the characteristic of high concentration of CODcr and NH3-N,and the proportion of the nutrition were imbalanced which can inhibit the activity of microorganism and lead to low efficiency of biological treatment,especially for the late leachate.So proper physicochemical method is needed to pretreat the leachate.If the landfill leachate is not properly treated,it will cause serious harm to human and ecological environment.Therefore,how to deal with landfill leachate economically and effectively has become a hot and difficult problem in the field of water treatment at home and abroad.In this paper,the landfill leachate from a domestic waste landfill is taken as the research object.Through the analysis of the water quality and comparative study of existing treatment processes,the coagulation-ClO2 oxidation-MAP process and the Fenton-MAP process were proposed.?1?Coagulation-ClO2 oxidation-MAP process:?1?Coagulation pretreatment:FeCl3 was selected as the coagulant,and the reaction conditions were optimized by single factor test:pH=4,FeCl3 dosage was 1.5g/L,and PAM dosage was 10 mg/L,precipitation time was 30minutes.Under these conditions,the removal rate of the CODcr and turbidity reached 36.93%and 84.69%,respectively.?2?ClO2 oxidation was used to treat the coagulation effluent:the dosage of ClO2 was 1000 mg/L,and reaction for 20 minutes,CODcr removal rates was45.73%.The chromaticity removal rate was 94.37%.?3?ClO2 oxidation-coagulation pretreatment:under the optimum conditions,the removal rate of CODcr and chromaticity is25.89%and 85.39%respectively.Comparison?2?shows that the degradation of landfill leachate by coagulation-ClO2 oxidation was better.?4?MAP process was used to treat coagulation-ClO2 oxidized water:Na2HPO4·12H2O+MgCl2·6H2O combination was selected.Under the condition of pH=9.5,n(Mg2+):n(PO43-):n?NH4+?=1.2:1.1:1.0,reaction for 20 min,the removal rate of NH3-N was 96.57%.?2?Fenton-MAP process:?1?Fenton pretreatment:the reaction conditions were optimized by single factor test:pH=4,H2O2 dosage was 20 mL/L,n?H2O2?:n(Fe2+)=4:1,and the reaction for 60 min.Under these conditions,the removal rate of CODcr reached 70.18%.According to the orthogonal experiment,the relationship of the four factors to the removal rate of CODcr in landfill leachate is as follows:pH>H2O2 dosage>n?H2O2?:n(Fe2+)>reaction time.?2?Fenton-MAP process:Na2HPO4·12H2O+MgCl2·6H2O combinat-ion was selected.Under the condition of pH=9.5,n(Mg2+):n(PO43-):n?NH4+?=1.2:1.0:1.0,reaction for 20 min,the removal rate of NH3-N was 98.13%.According to the orthogonal experiment,the relationship of the four factors to the removal rate of NH3-N in landfill leachate is as follows:pH>n(PO43-):n?NH4+?>n(Mg2+):n?NH4+?>reaction time.The coagulation process has the advantages of simple operation and low cost,which can remove the coarse suspended matter in leachate,organic matter in colloid state and heavy metal,etc.ClO2 oxidizing organic matter does not produce carcinogenic substances such as trihalomethanes.It is a kind of green oxidant and has broad application prospects.Fenton process can effectively remove the high concentration of CODcr in the leachate and reduce the chromaticity and turbidity.MAP process can remove NH3-N from leachate and generate magnesium ammonium phosphate precipitation.It is a kind of slow-release fertilizer with economic benefits,which realizes waste treatment and waste conversion.Therefore,the two technical routes of coagulation-ClO2 oxidation-MAP method and Fenton-MAP process proposed in this paper are feasible. |
PDF Full Text Request