Gestione sostenibile di un plume di contaminazione da solventi clorurati combinando interventi in situ fisici, chimici e biologici

The presence of chlorinated solvents in groundwater in industrialized and urbanized areas represents an environmental problem. An industrial plant in a densely populated urban neighborhood of a large Italian city has historically generated a widespread plume of tetrachlorethylene (PCE) in the downgradient aquifer. The management of the plume in the external areas required a thoughtful approach due to the complex hydrological context and limited accessibility. Through a multiscale and coupled hydrogeochemical approach, a remediation strategy was developed consisting in the application of different technologies that intercept the plume in consideration of the level of concentration and of the specific logistic and hydrogeological characteristics. On the one hand, coaxial groundwater circulation wells (CGC) coupled with air sparging (AS) have been used, in the areas with the highest concentration, to promote the in situ transfer of PCE from the contaminated matrices into a gaseous flow which is then treated on site. On the other hand, the injection of reagents into the groundwater has the aim of stimulating chemical reduction combined with rapid adsorption in situ, creating adsorbing areas of contaminants and stimulating the dechlorinating activity, in areas of intermediate concentration. The monitored natural attenuation was instead used in areas with a lower concentration. The development of an integrated conceptual model of the site (MCS) captures the specific geological and hydrochemical peculiarities of the site and supports the decision-making process. The multi-source model guides the configuration and localization of an advanced remediation strategy that is adapted to particular physicochemical conditions. The encouraging results obtained in the first phase of the activity show how, on the basis of a sufficiently robust conceptual model of the contaminated site, it was possible to identify the most suitable intervention technologies in a residential urban area with logistical constraints and particularly challenging potential secondary impacts.