Evolution of saturated hydraulic conductivity with compression and degradation for municipal solid waste.

Municipal solid waste (MSW) specimens were created from synthetic fresh MSW degraded in a laboratory scale enhanced degradation reactor. The degree of degradation and saturated hydraulic conductivity ks were measured to study the effects of compression and degradation on ks of MSW. The degree of degradation was characterized through the ratio of cellulose content to lignin content (i.e., C/L) and the loss ratio of volatile solid (i.e., DOD). ks of MSW specimens with different degrees of degradation was measured through triaxial permeameter tests under different confining pressures. It was found that, when the degradation time increased from 0month to 18months, ks decreased less than 1 order of magnitude for specimens with the same porosity (i.e., n=0.63 or 0.69). However, for specimens with the same degradation time, the decrease of ks could reach 2 orders of magnitude with n decreasing from 0.8 to 0.6. It indicates that compression has much greater influence on the reduction of ks than that of degradation. Based on the Kozeny-Carman model and first-order kinetics, a prediction model related to n and C/L (or DOD) of MSW was proposed to analyze the evolution of ks with compression and biodegradation. The methods to determine the values of model parameters were also proposed.