An estimated 170 million tons of municipal solid waste (MSW) were discarded in the United States in 1990. Of this amount, approximately 135 million tons (80 %) were ultimately disposed of in landfills (Franklin Assoc., 1988). Although landfills in the past have been associated with groundwater pollution and contamination of drinking water supplies, they remain the major municipal solid waste disposal method. Recycling is an important step in any solid waste management program, but to date, the amount of solid waste that is recycled is very minimal. Incineration appears to be currently in disfavor in the public's eye and relatively few incinerators are being constructed today. Therefore, landfill disposal of MSW will probably remain the major disposal option for the near future.
Today's state-of-the-art landfills are lined, often doubled lined, and are equipped with leachate collection systems. Leachate is the wastewater that forms as water percolates through solid waste. It can contain a wide variety of organic and inorganic compounds, some of which can be hazardous to human health and the environment. The current management practice for most landfills emphasizes minimizing the amount of moisture that enters the landfill. By doing so, the amount of leachate produced is decreased. In addition, the production of landflll gas, which contains potentially explosive methane and malodorous organic compounds is attenuated. Moisture is essential for the solid waste decomposition (stabilization) process in a landfill, a by-product of which is landfill gas. Minimizing the water entering a landfill will therefore suppress the production of both landfill gas and leachate and as an unintended side effect, diminish the rate of stabilization of the solid waste and extend the "active" period of the landfill.