A Study On Leachate Migration In MSW Landfill Under Biodegradation Effect

The hydraulic characteristics of the landfill body and the physical characteristics varied with the biochemical degradation of the municipal solid waste, which increased the difficulty of the leachate migration model establishing. By means of theoretical analysis, simulated experiment and numerical simulation, the effect of biodegradation on the solid matrix of the landfill body and the characteristics of leachate were analyzed. Then the author studied the water and solute migration rules considering the degradation of landfill body.Based on the dynamics of water and solute in soil, the author first analyzed the basic theories of leachate migration in landfill body, including the mechanisms of water and solute migration in landfill body. Then the simulated experiment was conducted, analyzing the initial characteristic of the municipal solid waste, the landfill settlement, leachate density and the dominant pollutants concentration in leachate. Based on the experimental study and theoretical analysis, the effect of degradation of organic waste on leachate migration was studied from the aspects of the solid matrix of the landfill body and the characteristics of leachate. Finally, the one-dimensional migration model of leachate in landfill body was established. At the same time, the difference method and the method of finite elements were employed to solve the model of the water and solute migration respectively. Then the water migration model was verified and analyzed by the data from simulated experiment.It was shown from the simulated experimental study that: the variety of the hydraulic characteristics of landfill body due to the degradation of the organic waste and landfill settlement, is the domination factor to affect the migration the leachate migration. On the other hand, the hydraulic conductivity of the landfill body was less affected by the density and viscosity.Taking in account of the variety of porosity and hydraulic conductivity in the process of the degradation of organic waste, the water and solute migration model in landfill body was established. The one-dimensional compress model and some reasonable hypothesizes was employed in this thesis. At the same time, taking the COD concentration in leachate as an example, the migration equation of organic pollutants in leachate was established taking in account of degradation of organic waste.The leachate quantity was predicted by the mathematical model. The results showed that due to the obvious heterogeneous of the municipal solid waste in landfill in the initial time, the experimental value and the predicted value had some difference. But in the later time, the experimental value and the predicted value was closer. This research exerts positive effects on the prediction of leachate quantity and quality in landfill and effective control measures for leachate pollution.