Siti contaminati. Esperienza negli interventi di risanamento

Applicazione di tecnologie innovative alla bonifica di siti contaminat

Effective decontamination of low dielectric hydrocarbon-polluted soils using microwave heating: Experimental investigation and modelling for in situ treatment

This work aims to obtain essential data for the in situ application of microwave (MW) heating for hydrocarbon-polluted soil remediation. For this purpose, lab-scale experiments were performed and a dedicated computer code was developed and applied to simulate the phenomena induced by a MW treatment. MW process was modelled by means of the mono-dimensional transient equations of energy taking into account the interaction between the electromagnetic field and soil and conductivity phenomena. The model was validated by comparison with results from lab-scale experiments. Main results indicate that, after a MW irradiation of 6 days, the electric field was reduced by about one third of its initial value at a distance of 60 cm and, as a consequence, soil temperatures equal to and lower than 180 °C were observed. Overall, the thermal effect of the MW treatment was observed to affect a maximum distance of about 120 cm, and this allows the achievement of the contaminant removal in the range 50-99% for a maximum distance of 80 cm from MW source. Results are of scientific and practical interest and can be used to guide the design of in situ MW treatments. The proposed model provides good prediction of the experimental data and it can be applied to investigate further operating conditions (soil types, incident electric field applied, remediation time). It represents a powerful and suitable tool to predict the effectiveness of the MW techniques

Lab-scale investigation on remediation of diesel-contaminated aquifer using microwave energy

Aquifer contamination with diesel fuel is a worldwide environmental problem, and related available remediation technologies may not be adequately efficient, especially for the simultaneous treatment of both solid and water phases. In this paper, a lab-scale 2.45 GHz microwave (MW) treatment of an artificially diesel-contaminated aquifer was applied to investigate the effects of operating power (160, 350 and 500 W) and time on temperature profiles and contaminant removal from both solid and water phases. Results suggest that in diesel-contaminated aquifer MW remediation, power significantly influences the final reachable temperature and, consequently, contaminant removal kinetics. A maximum temperature of about 120 °C was reached at 500 W. Observed temperature values depended on the simultaneous irradiation of both aquifer grains and groundwater. In this case, solid phase heating is limited by the maximum temperature that interstitial water can reach before evaporation. A minimal residual diesel concentration of about 100 mg kg-1 or 100 mg L-1 was achieved by applying a power of 500 W for a time of 60 min for the solid or water phase, respectively. Measured residual TPH fractions showed that MW heating resulted in preferential effects of the removal of different TPH molecular weight fractions and that the evaporation-stripping phenomena plays a major role in final contaminant removal processes. The power low kinetic equation shows an excellent fit (r2 > 0.993) with the solid phase residual concentration observed for all the powers investigated. A maximum diesel removal of 88 or 80% was observed for the MW treatment of the solid or water phase, respectively, highlighting the possibility to successfully and simultaneously remediate both the aquifer phases. Consequently, MW, compared to other biological or chemical-physical treatments, appears to be a better choice for the fast remediation of diesel-contaminated aquifers