Analysis on contaminants transport process through clay-solidified grouting curtain in MSW landfills

摘要

Clay-solidified grouting curtains are commonly used for remediation by containment or pollution prevention, in addition to their use as a barrier to water flow in municipal solid waste(MSW) landfills. A hydrologi-cal model of water flow and a hydrodynamic model of contaminant are presented to simulate the migration of leachate through clay-solidified grouting curtain in MSW landfills, with particular attention paid to the role of diffusive and adsorptive fluxes in contaminant transport. The models were applied to simulate the sensitivity of the curtain's behavior to changes in parameters, such as thickness, depth, permeability coefficient, diffusion coefficient, resistance coefficient and concentration, and also to demonstrate the contaminant distribution on the evolution of travel time and offset distance of clay-solidified grouting curtain in landfills. It is found that a part of leachate components stays or is retarded in clay-solidified grouting curtain by precipitate or exchange, the retention rate is closely related to composition of clay-solidified grouting curtain, more than 80%, and the maximum occurs at the cement-clay ratio of 2 : 4 under experimental conditions. Contamination distribution is variable on travel time and offset distance, the highest concentration takes place where the contamination intensity is nearest to the pollution resource or takes place at early middle period of transport, and the pollutant attenuates gradually. The results indicate that clay-solidified grouting curtain with a proper thickness, a low permeability coefficient and a high resistance coefficient might serve as a sufficiently effective vertical barrier against leachate seepage and contamination migration in MSW landfills.