Experimental Study on Chromium Containment by Admixed Soil Liner

Chrome tanneries generate large quantities of chromium-laden sludge that require proper disposal in engineered landfills to prevent contamination of subsurface soils and groundwater and reduce the risk to public health and the environment. This study investigates the feasibility of using a fine-grained soil as a suitable landfill liner material for the effective containment of chromium in the sludge leachate. Several series of laboratory permeability, adsorption, and column tests were conducted using soil without and with selected additives (rice husk, bentonite, and fly ash) to determine permeability and adsorption and transport of chromium in the soil. Permeability tests showed that the field soil amended with 17% rice husk and 2% bentonite provides the desired hydraulic conductivity of 10(-7) cm/s (or less) to minimize the leachate migration into the surrounding subsurface environment. The rice husk and bentonite admixtures significantly reduced the hydraulic conductivity of the soil from 3 x 10(-7) to 2.8 x 10(-9) cm/s, and this admixture was further tested for its effect on the adsorption and transport of chromium in the soil. The batch kinetics and column tests results showed that the soil possesses relatively high chromium adsorption capacity under natural or slightly alkaline condition. The batch tests showed that the amendment marginally improved the chromium adsorptive capacity of the soil. The column tests showed a slight increase in breakthrough time due to the presence of the amendment. The inclined base column tests showed that a mildly inclined liner configuration has a marginal effect on the chromium attenuation in the soil. Overall, this study showed that soil amended with 17% rice husk and 2% bentonite significantly decreased the hydraulic conductivity of the soil and slightly increased the adsorption of chromium, and therefore, has the potential for usage as a landfill liner in a landfill system to contain chromium contamination