Hydraulic Performance of Organo Clay Enhanced Sand Bentonite as Secondary Liner

Abstract

The leakage of petroleum from the storage tanks poses a serious threat to soil and groundwater. Hence an additional layer of impermeable material is usually provided as secondary containment systems in underground and above ground storage systems meant to store petroleum products. However the use of conventional mineral liner material is found to be ineffective for their use in secondary containment system to contain organic fluids. The conventional liner materials such as compacted sand–bentonite (SB) mixtures needs to be amended with materials of high organic sorption capacity. Therefore studies were carried out to assess the hydraulic performance of sand bentonite mixture amended with different percentages of organo clay (SOB) and to evaluate their possible use in secondary containment of petroleum product. The hydraulic conductivity of different SOB mixtures compacted at optimum conditions was evaluated with water and diesel as permeants. The coefficient of permeability was measured for various mixtures under different loads varying from 0 to 300 kPa. The permeability coefficient was evaluated both for loading and unloading cases. A decrease in the coefficient of permeability with diesel by an order of two, was observed on increasing the organo clay content from 0 to 10% in SB mix, where as a reverse trend was noted with water as permeant. The hydraulic performance of SOB mixture was found to be largely influenced by the proportion of organo clay, the nature of pore fluid and the applied pressure suggesting a need for careful proportion of mixture to be used as secondary liner.