Contaminant Mobilization from Polluted Soils: Behavior and Reuse of Leaching Solutions

Abstract

Soil and water contamination by toxic elements or molecules cause risks of chemical pollutions. These pollutions can heavily affect resources and activities of humans and ecosystems. By nature, the remediation of environmental pollutions is a constraint, because its application is hampered by high costs. Soil and groundwater remediation implements a variety of strategies, technologies, and practices to face the diversity and the complexity of every cases. Contaminant recovery is among the three main strategies implemented for the remediation of contaminated soils, and contaminant separation or mobilization by water is widely used for this purpose. As water solubility is the driving force of dissolution, selective chemical agents are used to enhance the mobilization of a wide range of contaminants in aqueous solution from permeable soils. This chapter provides the basic principles about the distribution of contaminants between the soil compartments and the transfer kinetics between these pools. Extracting agents, technologies, and methods used to mobilize priority contaminants are reviewed, considering performances, benefits, costs, and risks within a sustainable approach of reuse and of waste recycling. On the basis of an analysis of the existing literature, the possibility to reuse effective extracting agents and solutions is discussed, considering the overall performances, the costs of the separative methods implemented as well as waste management. However, multi-contamination, restrictive regulations or specifications, availability of appropriate installations and the lack of reported full-scale assessments limit the use of this strategy for the remediation of polluted zones. An example of field test using ultrafiltration for the recovery and reuse of surfactant solutions to flush creosote-contaminated soils is presented. Field tests show that the part of costs dedicated to extracting agents is often minor. In the short term, it is hardly compensated for by capital and operating costs of the separative technologies implemented for extraction solution regeneration.