**4. Conclusions**

The present study assessed the feasibility of performing soil flushing treatment with EDDS solution for remediating natural soils contaminated by Cu and Zn. An almost total removal of the bio-available fractions of these metals was achieved. Although the main factor that influenced the metals removal efficiency was the EDDS concentration in the extracting solution, this study proved that the effectiveness of the soil flushing was also dependent on several other factors, including contaminated soil depth as well as the different PTEs-EDDS complexes affinity. Moreover, tests under EDDS-deficiency conditions have further demonstrated that the Cu and Zn removal efficiency was lower due to their re-adsorption onto the soil and/or because of the occurrence of metal exchange processes. In order to take into account all of these aspects, it is essential to carry out bench-scale tests before performing a full-scale soil remediation treatment. Finally, the study proved that soil flushing, besides having a lower environmental impact and lower operative costs compared to soil washing (e.g., no soil excavation is required), is capable of achieving the same high removal efficiency, producing a smaller volume of contaminated spent solution and consuming a minor amount of chemical agents.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1660-4601/15/3/543/s1, Figure S1: Cu and Zn removal by soil flushing treatment at different times. 48 h; 96 h and at different values of bv—(a) Cu 4 bv; (b) Zn 4bv; (c) Cu 8 bv; (d) Zn 8 bv.

**Acknowledgments:** This study was carried out within the EUProject LIFE11 ENV/IT/000275 (ECOREMED).

**Author Contributions:** Marco Race and Alberto Ferraro performed all the tests, conducted all the analyses, and contributed to writing the manuscript. Massimiliano Fabbricino designed the study and participated in performing the tests as well as in writing the manuscript up to its final version. Antonio Panico supervised the whole work, edited the manuscript, and revised it critically. Alice Tognacchini participated in writing the manuscript and conducting analyses. Danilo Spasiano participated in performing the chemical analyses and edited the manuscript. Francesco Pirozzi participated in designing the study as well as in writing the manuscript and revising it critically.

**Conflicts of Interest:** The authors declare no conflict of interest.
