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 k were measured to study the effects of compression and degradation on k 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). k 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, k 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 k 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 k 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 k with compression and biodegradation. The methods to determine the values of model parameters were also proposed.