| The content of water and average degradable organic matter in the components of domestic waste in the loess area of Northwest China is low.The landfill generally uses loess as the covering material,and the output of landfill leachate is small.The leachate can be absorbed,deposited and combined by the overburden and the waste.The complexation fixes organic and inorganic pollutants;the heavy metals in the leachate can be controlled by chemical leaching and electric remediation;the landfill gas can be collected by the drainage system and then centrally treated,and the domestic waste pollutants are treated in situ disposal technology is a cost-effective way to achieve in-situ pollution control in landfills.There are a large number of iron sources in the landfill,and the dissimilar iron reduction reaction widely occurring in the anaerobic zone provides a feasible solution for in-situ pollution control of the landfill.The iron in the landfill consists of two parts,of which a small amount of natural iron source exists in the soil,and the remaining iron source is composed of metal components in domestic waste.The anaerobic landfill provides a suitable living environment for dissimilated iron-reducing bacteria,and Fe（Ⅲ）in domestic waste provides electron acceptors for the dissimilated iron reduction reaction of microorganisms.The complexed Fe（Ⅲ）can realize the vertical migration in the landfill with the leachate.Therefore,through the technical means of iron-containing leachate refilling,the fixation of heavy metals,the adsorption and purification of the leachate,and the domestic waste can be realized.CH4 reduction and other effects.The thesis studied the Fe content and morphological characteristics of the domestic waste landfill in Lanzhou New District,built a laboratory simulation landfill column as a bioreactor,simulated the degradation process of domestic waste in an anaerobic environment,and studied the degradation characteristics and characteristics of domestic waste.The layered distribution law of endogenous iron and heavy metals.By testing the adsorption and purification effect of different iron sources on the leachate and the fixing effect of heavy metals.On the basis of the reduction mechanism of dissimilated iron,we further explored the effect of different external iron sources on the control of CH4 produced by domestic waste in anaerobic landfill columns.Taking the domestic waste landfill in Lanzhou New District as an example,the effect of adding iron sources to CH4 The control effect of iron is calculated,and the application method of strengthening Fe recycling based on iron-containing leachate is studied.Research shows:（1）Research on the content and distribution characteristics of total iron in the domestic waste in the landfill of Lanzhou New District,the results show that the total iron content is between 15.7 and 24.5 g/kg.For waste samples with a landfill age of 2to 5 years,the proportion of Fe（Ⅱ）gradually increased with the increase of landfill age,from 43.8%to 58.0%,and the content rose from 7.6 g/kg to 13.4 g/kg.The four proportions of Fe in the landfill age of 0-5 years（acid soluble state,reducible state,oxidizable state,residue state）content ranges from 1.35%to 8.48%,14.69%to 33.22%,respectively,17.64%～38.45%,21.37%～65.66%.（2）Through the research on the environment of iron in the landfill column,the results show that the relationship between the natural settlement of domestic waste and the landfill age can be expressed by an exponential function to express the minimum degradation rate of the middle layer of the waste,and the fixed effect of heavy metals under high temperature and aerobic conditions better.The residual content of heavy metals in the middle layer of the waste was higher than that of other layers at 30 days of landfilling,and the level of heavy metals at the bottom of the waste was higher at the time of landfilling for 180 days.The content of heavy metals in each layer was positively correlated with the depth of landfill.（3）The experimental study on purification of leachate by adding iron source shows that the adsorption and purification effect of polyferric sulfate on leachate is better.The appropriate dosage is 100 mg/L,and the initial COD value is 3560 mg/L.The COD removal efficiency of L leachate is 72.92%.Ferric citrate has a better fixation effect on heavy metals.The effect of different iron sources on the control of CH4 production from domestic waste is determined by the presence of iron.The iron oxide group gradually enters the CH4 production stage at 10 d and reaches the maximum value of 25.95%at80 d.The methane production process is relatively prolonged.The CH4 concentration in the ferric citrate group was very low,reaching a maximum of 7.45%on the 30th day,indicating that the production of CH4 was inhibited to a greater extent.（4）Calculating the CH4 production process of the domestic waste landfill in Lanzhou New District,the results show that theoretically all Fe in the domestic waste participates in the reaction process of the CH4 precursor to reduce CH4 by 0.99～1.67 g,calculated according to the model The reduction of CH4 from the domestic waste sanitary landfill in Lanzhou New Area is 5.23×109～8.82×109 g,accounting for2.06%～3.47%of the total CH4 generation.Using technology based on the circulation of iron-containing leachate to increase the circulation efficiency of Fe,the final reduction effect can reach 5.93%～8.67%. |
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