Quantitative Study On Permeability Of Municipal Refuse Landfill Body

Landfill method will generate large amount of leachate with high concentration of pollutant, long duration and uneven flow and water quality change. Whereas this sort of leachate, if not treat properly, will become the source of underground water contamination, causing secondary pollution. In order to reduce the contamination of underground water, water amount and quality should be predicted to select the engineering measures of leachate collection and treatment. Research on the regulation of leachate production and migration is necessary for controlling and disposing the leachate. While as the essential parameter for leachate production and migration, the permeability coefficient has a great impact on the study of production and migration.This dissertation uses the methods of data collection, theoretical analysis to determine the main impact of municipal solid waste landfill body permeability. Based on this, through the indoor physical simulation temperature change of MSW landfill body, waste degradation discipline, the change law of municipal solid waste landfill body permeability in the main compression settlement stage, a mathematical model of municipal solid waste landfill body permeability is built.By searching domestic and foreign literature and theoretical analysis, analysis were carried out on the impact the refuse physical nature and landfill operations in different environments on landfill body permeability, selecting waste density, landfill height, effective pressure, waste deposition, waste composition and other factors as the key point for analyzing and demonstration. By theoretical analysis, it can be considered that the permeability MSW landfill body change is mainly due to their skeleton, which could be observed as settlement when reflected in the macro-phenomena, whereas the settlement is closely related to landfill depth and biodegradation of the organic components. Therefore the main factors on the permeability are the landfill depth and biodegradation rate of organic ingredients.Select 29,33,37,41,45℃as the parameter values for the degradation rate experiments of the indoor physical simulation of municipal solid waste landfill body. By researching pH value, COD, NH3-N concentration in the leachate and CH4 concentration in the landfill gas, determine the stage of the refuse stated. And then use carbon atoms conservation to calculate the degradation rate of the MSW. After statistical analysis of the calculation data of MSW degradation rate, it concluded that degradation rate accord with growth curve in single temperature, and degraded the fastest at 41℃and 45℃, showing similar the degradation rate. When temperature is over 41℃, the degradation rate could be calculated according to that in 41℃.This study collected newly dumped refuses from Changan Landfill to set up indoor physical simulation column experiments on temperature variation, in which the temperature of refuse column, COD of leachate, NHx-N and concentration of CH4 were monitored. According to the refuse degradation processing, the whole experiment was divided into aerobic degradation stage, acidogenic stage of anaerobic degradation and methanogenic stage of anaerobic degradation). Temperature in refuse columns increased first and then decreased as a whole. Temperature increased drastically at aerobic degradation stage. During the acidogenic stage of anaerobic degradation, temperature changed repeatedly because of small amount of heat was released by anaerobic process, and the maximum temperature occurred at the first part of acidogenic stage of anaerobic degradation. While in the methanogenic stage of anaerobic degradation, the temperature kept decreasing.The variation of landfill's permeability could be divided into two stages:the main compression settlement stage and the second compression settlement stage. The main impact factors of these two stages were landfill height and refuse degradation rate, respectively. In lab simulation, landfills under four different pressure conditions were chosen to analyze the permeability characteristics during main compression settlement stage. It was shown that permeability analysis results under four pressures were consistent with Darcy's law and COD variation happened in acidogenic phase, whose influence could be ignored. With the exception of the experiment under no external pressure, the permeability characteristics in other landfill simulations during the main compression settlement stage were roughly following the natural exponential law. Under the assumption that permeability of landfill's body is kept essentially constant in horizontal direction, it can be assumed that the change of permeability conform to natural exponents in vertical direction; Based on the main factors'contributions to permeability in the two stages, the mathematical models of MSW permeability are established.