Control of hydraulic conductivity and chromium mobility in soil-drilling fluid mixtures by polyacrylamide

Abstract

Land disposal of water-based oil and gas well drilling fluid is an cause of environmental concern due to the high salt concentration and potential chromium (Cr) contamination of groundwater. Safe land disposal of waste drilling fluid and remediation of drilling fluidaffected soils require an adequate hydraulic conductivity for the leaching of excessive salt accumulation and immobilization of Cr to prevent groundwater contamination. Anahuac and Crowley sandy loam surface soils sampled near the southern Louisiana-Texas state line were treated by a batch method with the drilling fluid and two cationic polyacrylamides (PAMs). The PAMs were used as amendments to increase the hydraulic conductivity and the adsorption capacity of the drilling fluid-affected soils for the Cr organic complex. Hydraulic conductivity of the soil-drilling fluid mixtures and light transmittance of the leachates increased, while the Cr mobility decreased by the PAM treatment. The larger PAM molecules were more effective in improving the hydraulic conductivity of the soil-drilling fluid mixtures than the smaller molecules. The Anahuac soil-drilling fluid mixtures showed a higher hydraulic conductivity and lower Cr mobility than the Crowley soil-drilling fluid mixtures apparently because of the higher organic matter content and lower sodium adsorption ratio (SAR) of the former. The hydraulic conductivity, light transmittance, and Cr mobility data indicated that the PAM treatment and soil organic matter enhanced the flocculation and aggregate stability of the soil-drilling fluid mixtures and contributed to the immobilization of the Cr added as lignosulfonate to the soils.