Modeling Of Landfill Generation And Migration Process And Its Application

Pollution control of landfill gas and its recovery is a urgent problem in China,because over 90% municipal solid waste were disposed by landfill. Landfill gasproduction and migration were investigated by jointed methods of theory analysis andexperimental tests in this project. Waste decomposition and landfill gas generation process under differentcomposition and temperature conditions was investigated by a MSW landfill lysimeter.The experiment results show that higher temperature and adding wastewater sludge toMSW can accelerate organic wastes decomposition and landfill gas production. Thegas production rate declines rapidly is the significant feature of gas production processof MSW which major content is kitchen waste. This results is quite different from thatreported by abroad researchers. So the rapid decline of gas production after landfillclosure will cause a deep effect on the design and operation of LFG recoveryprojects. On the base of the conversion rate of biodegradable organic waste, a new methodfor calculating LFG production has been proposed, in which the biodegradation rate oforganic waste was estimated just by volatile solid content of MSW which can bemeasured easily. The method takes the advantage of simplicity, convenience and theeasiness of determining the input data. And LFG production at different decompositionphases of MSW also can be determined, by which relation between LFG production,and waste components was established. An experimental method for measuring air permeability Kh,Kv of compactedMSW under different compacted densities, water contents and decomposition stage bya landfill lysimeter has been proposed. The experimental results indicate that compacted MSW is a typical heterogeneous porous media, the average air permeabilityKh in the horizontal direction is 7.5~20.0 times of Kv in the vertical direction(compacted direction); Air permeability Kh,Kv decline with the increase of compacteddensity in exponential relation and with water content in liner relation; Airpermeability of moderate decomposed MSW is close to the fresh MSW, and both aremuch lower than the air permeability of decomposed MSW. A mathematical model for LFG migration under a vertical extraction well wasproposed. By using the model, pressure distribution of LFG around a verticalextraction well in a landfill can be calculated, and effects of permeability, radius of III英文摘要influence of extraction well, LFG flow and the buried depth of the well for collectionsystem design also be analyzed. The calculating results for the given LFG extractionsystem show that landfilled MSW is a typical heterogeneous porous media, it cannotbe taken as isotropy, else will cause significant errors; It was concluded that thereasonable radius of influence of a extraction well is 35.0~40.0m for most landfill sites,and the optimal buried depth of extraction well is about 80% of total depth of waste forvertical extraction system.