Reuse and disposal of EDDS solution after chemical washing of contaminated soils

The paper investigates the most prominent aspects of the soil washing technique applied to lead contaminated soil, using Ethylenediamine-disuccinic acid (EDDS) as a chelating agent. The entire treatment cycle is investigated in the laboratory using a continuos stirred -tank reactor. Different molar concentrations of the washing solutions and the efficiencies of varying slurry concentrations are examined, varying also the pH conditions. The regeneration and re-use of washing solutions are also tested. Finally disposal of washing solution is investigated and ecotoxicity tests are performed on the decontaminated soil. Obtained results allow to define the parameter for the design and exercise of a full scale reactor for site decontamination, minimizing the cost-to-efficiency ratio, and to verify that EDDS-exhausted solutions are no longer biodegradable, while regenerated solutions can be easily disposed in a municipal wastewater treatment plants. Ecotoxicity tests confirm the reduced toxicity of decontaminated soil respect to the amount of extracted lead.