The Role of Natural Clays in the Sustainability of Landfill Liners

Abstract

Engineered synthetic liners on their own cannot protect the environment and human health against landfill leachate pollution. Despite their initial impermeability, they are susceptible to failure during and after installation and have no attenuation properties. Conversely, natural clay liners can attenuate leachate pollutants by sorption, redox transformations, biodegradation, precipitation, and filtration, decreasing the pollutant flux. Depending on the clay, significant differences exist in their shrinkage potential, sorption capacity, erosion resistance and permeability to fluids, which affects the suitability and performance of the potential clay liner. Here, the physico-chemical, mineralogical and geotechnical characteristics of four natural clayey substrata were compared to discuss their feasibility as landfill liners. To study their chemical compatibility with leachate and rainwater, hydraulic conductivities were measured every ≈2 days spread over 7 weeks of centrifugation at 25 gravities. At field-scale, this is equivalent to every 3.4 yrs spread over 80 yrs. All the clayey substrata had favourable properties for the attenuation of leachate pollutants, although different management options should be applied for each one. London Clay (smectite-rich) is the best material based on the sorption capacity, hydraulic conductivity and low erodibility, but has the greatest susceptibility to excessive shrinkage and alterable clay minerals that partially collapse to illitic structures. Oxford Clay (illite rich) is the best material for buffering acid leachates and supporting degradation of organic compounds. The Coal Measures Clays (kaoline-rich) have the lowest sorption capacity, but also the lowest plasticity and have the most resistant clay minerals to alteration by leachate exposure.

Hydraulic and Swell–Shrink Characteristics of Clay and Recycled Zeolite Mixtures for Liner Construction in Sustainable Waste Landfill

“…As it was previously reported [18][19][20][21][22] locally available clays are often suitable for compacted clay liner construction, mainly compacted wet of optimum (on wet side) of the Proctor curve, forming water content greater than the plastic limit [23]. However, in some cases, the local clay substrates may not allow reaching the required values of K s in the full range of molding water contents [24] or for the selected values of initial water content, usually after compaction dry from optimum (dry side of the Proctor curve) [18,20].…”

Study on Osmotic Consolidation and Hydraulic Conductivity Behavior of an Expansive Soil Inundated with Sodium Chloride Solution

“…Encroachment of seawater in coastal places during current or geologic eras, as well as salt dissolving in salt domes/salt beds, may result in saline water in aquifers [20,26]. When nonsaline clays (pore water salt concentrations ranging from 0 to 900 ppm) are utilized to build impermeable clay barriers, their pore water salinity may be lower than that of external chemical reservoir solutions [20,27]. Variances cause the osmotic suction difference between the two-solution phase dissolved salt content between the pore water of clay barriers and the chemical reservoir solution [3,28].…”