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

摘要

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_s were measured to study the effects of compression and degradation on k_s 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_s 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 0 month to 18 months, k_s 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_s 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_s 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_s with compression and biodegra-dation. The methods to determine the values of model parameters were also proposed.