Calcium salts and cationic organic polymers as amendments for remediation of drilling fluid affected soils

Potential negative environmental effects of disposing waste drilling fluid (DF) on land are a concern due to the high content of salt and toxic metals such as chromium (Cr) and barium. Changes in physical and chemical properties of two Southern Coastal Plain sandy loam soils (Anahuac and Crowley) after the addition of finely ground hematite as an alternative DF weighting material for barite were determined. Also, the effects of amendments with calcium carbonate (CaCO{dollar}sb3),{dollar} gypsum, cationic organic polymers (494C and 587C produced by CYTEC Industries Co., Indianapolis, Indiana), and calcium phosphate (CaHPO{dollar}sb4){dollar} on the hydraulic conductivity (HC) and mobility of Cr of soil-DF mixtures were tested by column experiments in the laboratory. The oxidation of Cr (III) to Cr (VI) in soils was determined as a function of the addition of manganese oxide.; Addition of hematite to 3% increased the HC of soils but greater amounts reduced it. Hematite addition had no significant effect on aggregate stability and adsorption of zinc and phosphate.; Addition of 3% DF to soils changed them from being acidic and nonsaline to being saline (Anahuac) or to being saline-sodic (Crowley). Amendments of soil-DF mixtures with CaCO{dollar}sb3,{dollar} gypsum, and cationic organic polymers increased HC but decreased Cr mobility. The HC and Cr mobility of soil-DF mixtures were increased by treatment with CaHPO{dollar}sb4.{dollar}; The oxidation of Cr (III) to Cr (VI) in soils increased with increasing content of Mn oxide. Crowley soil with higher content of Mn oxide and lower content of organic matter had greater oxidation capacity for Cr (III) than Anahuac soil.; Results of this study indicate that amendments with CaCO{dollar}sb3,{dollar} gypsum, and cationic organic polymer for safe land farming of DF and reclamation DF-affected soils can be practiced. Application of phosphate fertilizer on DF-affected soils should be minimized to prevent the contamination of groundwater and surface water from Cr. Soils with high contents of organic matter and low contents of Mn oxide are recommended for potential land farming media of DF. Consideration should be given to the effects of hematite on the HC of soil-DF mixtures, when land farming of DF containing hematite.