Field air permeability and hydraulic conductivity of landfilled municipal solid waste in China

摘要

The successful design and operation of in situ treatment systems using air and water additions for sustainable landfilling are constrained by a lack of knowledge of the key parameters, such as field air permeability and hydraulic conductivity of landfilled municipal solid waste (MSW). This work provides data on the field air permeability k_a and hydraulic conductivity K_w of MSW obtained by conducting short-term air and water injection tests at a landfill in Beijing, China. The k_a and K_w values are found to in the range of 1.2 × 10~(-13) -1.9 × 10~(12) m~2 and 5.9 × l0~(-7)-7.2 × 10~(-6) m s~(-1), respectively.Both k_a and K_w decreased significantly with landfill depth due to the increase in overburden pressure and the finer particles of the waste in deeper layers, leading to a lower porosity of waste. The higher moisture saturation in the deeper layers also contributed to the decrease in k_a. To compare the permeability with respect to air and water, the water permeability k_w was calculated based on the estimated K_w and was found to be approximately three orders of magnitude smaller than the corresponding k_a for waste at the same layer. The differences in k_w and k_a may be due to the relative air permeability, the potential short-circuiting of air and active production of biogas, which undermine the relationship between k_w and k_a. Therefore, to successfully design and operate air and water addition systems in a landfill, in situ measurements of the air permeability and hydraulic conductivity are essential.