The treatment of excavation by-products has been studied using Fenton and Heterogeneous Fenton processes, by the addition of zero-valent iron nanoparticles (nZVI) as catalyzer. This study demonstrated that both methods could significantly reduce the organic content of the liquid extract from excavated soils. Operating parameters, such as pH and catalyzer/oxidant (w/w) ratio, were varied to investigate their influence on the Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) removal efficiency. In addition, Biochemical Oxygen Demand (BOD) was evaluated before and after the treatment. The optimal conditions found for conventional Fenton process were: H2O2/COD= 1 (w/w), Fe(II)/H2O2= 0.1 (w/w) and pH= 2.5, whereas for Heterogeneous Fenton were: H2O2/COD= 0.75 (w/w), nZVI/H2O2= 1.5 (w/w) and pH= 3. Heterogeneous Fenton resulted more efficient with respect to conventional Fenton, leading to a TOC and COD removal efficiency equal to 75.95 and 85.52%, respectively. The BOD28/COD ratio after Heterogeneous Fenton increased by about 200%, indicating the suitability of this oxidation process to achieve a biodegradability increase.