Research For Absorption Degradation And Catalysising Oxidation Technology Of Domestic Landfill Leachate

Landfill leachate is a kind of organic wastewater producing during the course of rubbish landfill, pollutants concentration of it is very high and constituent of pollutants is perplexed. Furthermore, leachate yield and water quality change very large. So leachate treatment is always a difficulty all over the world. According to actual demand for leachate treatment, in order to reduce leachate yield, lower leachate treatment cost, improve leachate treatment effectiveness, this thesis research the ways of reducing leachate yield and chemical catalysis oxidation technology for leachate treatment. The effect of fillers with absorption on leachate yield, velocity of rubbish degradation and water quality of leachate were studied by adding fillers in rubbish landfilled. Then, the thesis researched the effect and cost of polymer aluminum chloride (PAC) coagulation and Fenton oxidation for leachate treatment, determined dosage of Fe²⁺, H₂O₂ and PAC for optimal leachate treatment effect. Moreover, a lot of metal ions catalyst were synthesized and used to treat leachate with ozone, catalyst with better treatment effect was selected. On the basis of the reaearch results, the optimal reaction conditions of metal ions catalysis and ozone oxidation for leachate treatment were determined. The experimental results can supply the academic and technological direction for engineering application of reducing leachate yield technology and catalysis ozone oxidation technology for leachate treatment.In the research of reducing leachate yield, saw powder, activated carbon, zeolite and waste newspapers were added into rubbish separately, at the same time, the same condition landfill rubbish layer no fillers adding was taken as contrast reactor, leachate yield, velocity of rubbish degradation, COD and NH_3-N concentration of leachate were measured. The experimental results indicate that fillers can reduce leachate yield and accelerate rubbish degradation, as for one liter rubbish, adding saw powder in mixed style into anaerobic landfill rubbish can reduce 100-200mL leachate. Furthermore, after 180 days, increased volume for fillers accelerating rubbish degradation was larger than decreased volume for fillers occupying.The research results show that fillers can reduce content of COD and NH_3-N in eachate. There isn't obvious difference from capability of absorpting organic pollutants among saw powder, activated carbon and zeolite. But saw powder has stronger ability in absorpting NH3-N than activated carbon and zeolite. Dissolved heavy metal ions, such as Cu²⁺, Fe²⁺, Zn²⁺ can be absorpted easily by saw powder and activated carbon, which can lower heavy metal ions concentration in young leachate. In total, saw powder is more suitable filler than activated carbon, zeolite and waste newspapers. The experimental result of saw powder obsorption pollutants in leachate indicate that saw powder can complete absorpting COD in leachate in 3 hours at the temperature of 20℃, the relationship of absorption quantity and COD equilibrium concentration of leachate conform Freundlich absorpting isthermal formula. The capability of saw powder absorpting COD is 142.44mgCOD/g saw powder; saw powder can complete absorpting NH3-N in leachate in 1 hour at the temperature of 20℃, the capability of saw powder absorpting NH3-N is 36.36mg NH3-N /g saw powder, available absorpting isthermal formula cannot express the regular of saw powder absorpting NH3-N.The experimental results of PAC coagulation and Fenton oxidation treating leachate show that the optimal reaction conditions for Fenton oxidazing pollutants in leachate are pH=3.5, the mole ratio of H₂O₂ and Fe²⁺ is 0.6, the mass ratio of H₂O₂ and COD is 3.0, reaction time is 4 hours; the optimal dosage of PAC for removing pollutants in leachate by coagulation is mPAC/mCOD(the mass ratio of PAC and COD)=0.6. As for the same water quality of leachate, there isn't obvious different from COD removal rate of leachate. But the cost of coagulation/Fenton process for leachate treatment is generally lower 62.6 yuan than the cost of Fenton/coagulation process for one ton leachate.In order to synthesis high efficiency catalyst to catalysis ozone oxidation pollutants in leachate, Cu²⁺, Ni²⁺,Co²⁺, Cd²⁺, Cr³⁺ loading-ions catalysts were made with carrierγ-Al₂O₃. The experimental result of the five kinds of catalysts catalysis ozone oxidation pollutants in leachate indicate that Cu²⁺ catalyst catalysis ozone oxidation can remove most COD of leachate in the five catalysts, Ni²⁺ catalyst can remove most NH3-N of leachate in the five catalysts. On the basis of the research result, 75 kinds of Cu²⁺/ Ni²⁺ double component catalyst were made under different impregnant concentration and mole dosage to take advantage of Cu²⁺ catalyst and Ni²⁺ catalyst separately in catalysising ozone oxidation pollutants in leachate. The experimental result indicate that in the 75 kinds of catalysts, the catalyst which can remove most COD and NH_3-N of leachate was made on the condition of impregnant concentration was 0.25 mol/L, mole ratio of Cu²⁺ and Ni²⁺ was 1, roasting temperature was 800℃. Metal ions mole loading-rate of this catalyst is 2.6764%. Further experiments for catalysising ozone oxidation pollutants in leachate show that this catalyst can remove COD in leachate on the condition of pH=9, the ratio of ozone dosage and COD content in leachate is 0.55, the ratio of catalyst dosage and COD content in leachate is 3. On this condition, COD removal rate is 75-25.2% corresponding COD concentration is 515-12115mg/L in leachate. Biodegradability of leachate can be improved obviously through Cu²⁺/ Ni²⁺ double component catalyst catalysis ozone oxidation pollutants in it. Before catalysis ozone oxidation, BOD₅/COD of leachate is 0.085-0.145, it increases to 0.31-0.475 after catalysis ozone oxidation.