Applying The Physical-chemical Method To Treat The Effluent Of Biological Treatment Of Landfill Leachate

The research of applying physical-chemical method to treat the effluent of biological treatment of landfill leachate is introduced in this paper. The concentration of COD of the effluent of biological treatment is 1000¹500mg/L.Because the quality of the effluent can't meet the emission control standard, we choose the combination process of coagulation method, oxidation method and absorption of fly ash method to decrease the CODs, organic contaminations that can not be further biologically removed and heavy metal ions of the wastewater.In the experiment of applying coagulation method to treat the landfill leachate, Fe₂(SO₄)₃ was screened out from four coagulants (Al₂(SO₄)₃, FeCl₃, Fe₂(SO₄)₃, PAC). The main optimized parameters including the dose of coagulant, KMnO₄ and PAM, and pH were explored and optimized. When the experiment was operated according as the optimized parameters, the decrease ratio of COD is 27.4% by using coagulation as deep treatment and is 11.4% by using coagulation as pretreatment. At the same time, the absolute decrease value of COD by using coagulation as pretreatment is 600mg/L higher than by using coagulation as deep treatment. Accordingly coagulation can be used as pretreatment to lighten the organic load of the latter biological treatment and improve the character of landfill leachate, which can make it is easy to treat by biological treatment.There are many hazardous organic contaminations in landfill leachate;some physical-chemical method can not eliminate the contaminations completely. Oxidation treatment can decompose part of the organic contaminations and reduce the pollution radically. A series of test was done to improve the efficiency of H2O2, reduce the cost and confirm the optimized parameters of the oxidation. In the forepart of the process, oxidation treatment can insure the water quality meet the emission control standard. Furthermore, oxidation treatment can be used as pretreatment to improve the efficiency of biological treatment. In the experiment, oxidation treatment was used as deep treatment to treat the effluent of biological treatment and the decrease ratio of COD is 66%. Some heterogeneous catalysts were also attempted to catalyze hydrogen peroxide to produce·OH, but the efficiency is low.The adsorption treatment by using fly ash was tested after oxidation treatment, and the parameters that can influence the decrease ratio of COD were optimized. The results of theadsorption with fly ash coincide with Freundlich adsorption isotherm and Langmuir adsorption isotherm.The landfill leachate after coagulation, oxidation and adsorption treatment can meet the second emission standard. The biological treatment efficiency was improved by oxidation treatment. Fly ash can reduce the toxicity of the animalcule by decrease large part of heavy metal ions. The CODcr of landfill leachate can be sequentially decreased by using routine biological treatment.