A Numerical Model of the Soil Flushing Remediation in Heavy Metal Contaminated Soil

This paper presents a 1D numerical model developed to simulate the EDTA chelation process of metal (lead) applied to a soil flushing remediation action. The model considers the non–stationary conditions, typical of unsaturated soil. Flow and transport equations are solved simultaneously. Metal mobilization is evaluated considering both the chemical aspects of chelating agents and the characteristics of the different soil fraction at which the metal can be bound. A system of first order reactions is implemented and, for each fraction, two different mobilization kinetics (slow and fast) are considered. The model was calibrated and validated using laboratory experimental data. Results confirm that the model can represent an evaluable tool to assess the feasibility of soil flushing application for heavy metals contaminated soil, especially in the case of surface layer contamination. It is useful to optimize the operating parameters (chelating dosage, application mode and treatment thickness) in order to achieve the maximum treatment efficiency while minimizing potential environmental impacts.