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Laboratory remediation experiments were carried out through the use of Prefabricated Vertical Drains (PVDs) to remediate soil contaminated with heavy metals. In the ground with lower permeability, the extraction of contaminants and the transmission of fluids are difficult; thus, to improve the injection or extraction of surfactants and to overcome difficulties due to micro pores in the soil, PVDs were used. For band-type drains, experiments comparing the effectiveness of filters coated with reactive material with the effectiveness of uncoated filters were conducted, and for cylindrical-type drains, experiments comparing the effects of the injection of surfactants were carried out. The heavy metal contaminants used in the experiments were Cu, Pb, and Cd, and concentrations over time were measured to assess the remedial efficiency. In the experiments, the initial concentrations were determined in consideration of the Korean Soil Contamination Warning Standards. The results from the experiments showed that the removal rates for Cd and Cu were 40% while that for Pb was 35% in the case of extraction alone. In the case of extraction with the application of reactants, the removal rates for Cu and Cd were 60% while that for Pb was 55%. In the case using both the reactant coating and cleansing agent injection, the removal rates were 74%, 65%, and 58% for Cd, Cu, and Pb, respectively.
Introduction The method for the remediation of contaminated ground should basically be determined according to in-situ conditions and the properties of the contaminants. Methods to remediate soils contaminated by heavy metals are classified into physiochemical treatment techniques (such as pump and treat, solidification and stabilization, and vitrification), phytoremediation techniques (such as land farming), and biological treatments. However, these techniques have disadvantages such as the long duration needed for remediation, high costs, and potential risk of secondary contamination from chemical agents applied, and in the case of the actual remediation of in-situ ground having lower hydraulic conductivity, the remedial efficiency may decline rapidly or even make it difficult to use a particular remedial approach. The transmission of fluids and extraction of contaminants from contaminated soils with high concentrations of heavy metals or harmful materials would be difficult, and the voids in soils of lower permeability, such as silt or clay, are typically very small, limiting the injection or extraction of surfactant or desorption agents. Thus, technical methods for the remediation of contaminated soils and construction techniques to perform the remediation of soils are required (Korean Ministry of Environment, 2009).
The adsorption capacity of Prefabricated Vertical Drains (PVDs) for contaminants was assessed by conducting adsorption experiments on reactive material coated on filters of the drains and by comparing the results of the experiments with the isotherm adsorption model. Regarding the remediation system with PVDs, the remedial efficiency was measured through cylindrical chamber experiments. The reactive material used in the experiments was a natural zeolite, and the contaminants were Cu, Pb, and Cd. The choice of three kinds of heavy metals was due to a contamination survey. Incheon was distributed in three heavy metal contaminated areas.
This study was conducted to determine basic data to be used for geotechnical remediation engineering by analyzing the characteristics of factors affecting the contaminated soils in the remediation process through the use of PVDs and by reviewing the removal effects obtained through laboratory experiments.
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