In-Situ Landfill Gas Permeability Of Older Municipal Solid Waste In An Arid Region

摘要

An experimental study was performed at the City of Phoenix Skunk Creek Landfill to determine the in-situ gas permeability of 22 to 27 year old municipal solid waste. The permeability of old waste in an arid environment is not well known and there are few related studies on this topic. The study area receives average annual precipitation of only 7.66 inches. Two sets of experimental probes were installed adjacent to gas collection wells in different closed waste cells at the landfill. Waste in both study locations was dry, and moderately to poorly compacted. The field data was analyzed using a one-dimensional radial flow equation. The resulting values were verified using an axi-symmetrical vapor flow computer model. Computer modeling also provided an estimate of the gas flow pattern in the area of the collection wells. The values obtained from this study indicate that older solid waste has relatively high gas permeability. In addition, the 27-year-old waste was more permeable than the 22-year-old waste. The study results suggest that, in addition to variations in waste density, decomposition of the organic portion of the waste mass may increase the waste's void ratio, resulting in greater permeability. The study data was also used to estimate the radius of influence of the gas collection wells installed in these closed cells, based on vacuum distribution in the waste. The results of this experiment lead to some conclusions concerning the design of landfill gas collection systems in arid regions.