Double liner systems are now required for new hazardous waste landfills and impoundments to prevent groundwater contamination causedby leachate. However, uncertainty always exists about the longevityof the synthetic flexible membrane liner, and the compacted clay components of the liner system may release some seepage in time under a sustained hydraulic head. The mechanisms of contaminant retention by clay minerals are not fully understood, and the attenuation capacity of any containment system is finite. In addition, diffusion through the clay liner under a concentration gradient may increase the rate of contaminant migration into the environment above that owing to advection alone. Electro-kinetic counterflow may be an effective measure to stop the migration of contaminants under a hydraulc gradient. An electro-kinetic fluid flow barrier can be created by the continuous or periodic application of an electrical gradient across a compacted clay liner. A coupled flow theory to describe the simultaneous flows of water, electricity, and contaminant ions under the influences of hydraulic, electrical, and chemical gradients has been developed by using the formalism of the thermodynamics of irreversible processes. An experimental testing program demonstrated the existenceof electro-osmotic flow in partly saturated compacted clay and provided a basis to evaluate the validity of the theoretical predictions. An electrical gradient may move some inorganic species in soils much more effectively than hydraulic gradient. An electro-kinetic flowbarrier halted the migration of the cation but accelerated that of the anion under laboratory testing conditions. This paper appears intransportation research record no. 1288, Geotechnical engineering 1990.
Samenvatting