When waste is dumped in a landfill it undergoes aerobic phase initially and then an anaerobic phase which is dominant. During the anaerobic phase, organic material is converted to methane which forms more than 90% of the landfill gas. Leachate formation is the result of the removal of soluble compounds by non uniform and intermittent percolation of water through the refuse [El-Fadel, Met al.1997]. Laboratory and field studies have shown that there is microbial degradation of the organic content in the leachate under both aerobic and anaerobic conditions are less toxic [Pohland, F. G.1986].