SOIL BENTONITE LINER TO CONTROL MIGRATION OF POTASSIUM IONSMEGHA N KULKARNI1, C. RAMAKRISHNEGOWDA2, H. S. NANDA AND PUVVADI V. SIVAPULLAIAHAbstract Compacted soil liners amended with bentonite are widely used to minimize migration of pollutants. The thickness of the liner is designed based on the rate of migration of contaminants through the selected liner. The rates of transport of contaminants depend both on the hydraulic permeability of the compacted liner and diffusion rates of pollutants. The advection diffusion mathematical model is used to assess the rates of transport of contaminants through the soil liner. The rates of migration of ions by advection process can be assessed knowing the porosity of the soil, hydraulic head and permeability of the soil. But the rates of migration by diffusion depend on diffusion coefficient and retardation factor of the ions for the selected liner. These transport parameters can be obtained by performing soil column tests and obtaining breakthrough curve. In this study, it is proposed to obtain breakthrough curve of potassium ions in locally available soil amended with 10% bentonite. Theoretical breakthrough curves can be generated using mathematical models with a set of assumed values of diffusion coefficient and retardation factor. The actual values are those which yield the theoretical curves close to experimentally determined Break through curves from column test. These values are determined for potassium ions, which is not retarded heavily and hence give more conservative values. The thickness of the liner is decided for any given designed life of the liner. The locally available soil which is not directly suitable as liner due its higher permeability is amended with bentonite is selected as liner and thickness is established for different designed periods.
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