Permeability Of Municipal Solid Waste In Bioreactor Landfill With Degradation

Bioreactor landfills are operated and controlled to accelerate refuse decomposition, gas production and biological stabilization of the municipal solid waste (MSW). Leachate recirculation in bioreactor landfill creates a favorable environment for rapid microbial decomposition of the biodegradable components of solid waste. Therefore, clear understanding of the mechanism of moisture movement within the solid waste would be necessary for successful design and operation of the bioreactor landfill. Permeability is an important parameter during the design of leachate collection and recirculation system. In the current study an experimental program was designed to determine the variation of coefficient of permeability of MSW with degradation and to determine the influence of density and cover soil on permeability of MSW. MSW samples representing various stages of decomposition were generated in eight laboratory scale reactors operated under conditions designed to simulate decomposition in bioreactor landfills. The reactors were destructively sampled at the end of each phase of degradation based on the reactors methane production rate curve, PH and volatile organic content. A series of constant head tests were performed on the representative MSW samples at different stages of decomposition to determine the variation in permeability with degradation. Tests were repeated at three densities and two percentages of soil. Test results indicated a decrease in particle size with degradation which was mainly due to the breakdown of matrix structure of individual components within MSW. The coefficient of permeability of MSW decreased from 0.0088 cm/s (Phase I) to 0.0013 cm/s (Phase IV). There is an overall decrease in the permeability with increase in density and percentage soil. The trend is the same for the samples at each phase of degradation. The percentage decrease in permeability is much higher when there is combined effect of both increase in density and increase in percentage of cover soil.