Design of Soil Remediation Techniques from Column Leaching Test Results

Abstract

T he soil remediation at a contaminated site requires knowledge of contaminant transport parameters and processes. T his paper presents the determination of transport parameters from column leaching tests in context with two soil remediation techniques i.e., soil washing and immobilization. To evaluate the soil washing technique, t he column leaching tests on the polluted soil were conducted with diluted acid solutions of hydrochloric acid, ethylene diamine tetraacetic acid and ferric chloride to evaluate the leaching efficiencies of the selected leaching solutions. It was observed that the efficiency of diluted ferric chloride solution was higher as it removed the higher percentage of metals from the soil. From these test results, the contaminant transport parameters i.e., retardation factor and dispersion coefficient were determined which are useful to calculate the volume of leaching solut ion that will be required for soil washing at a site. As part of immobilization study on this soil, the soil was mixed with the selected amendments (lime, sodium hydroxide and cement) to increase the pH of the soil to 10 and the retardation factors were estimated through batch leaching test results. The retardation factors of different metals obtained with lime addition were found higher than the other amendments.To analyze the long-term stability of the amended mixtures, the leaching tests were conducted on amended soil samples and the immobilization efficiencies were estimated. It was found that the immobilization efficiencies were higher with lime addition and also concluded that the immobilization effiencies are directly related to retardation factors.