Minor attention was reserved in the past to the environment, due mainly to a profit logic prevalence combined with a limited knowledge on the negative effects introduced in the environment by the actions made. This led to the deterioration of aquifers and soil quality in different regions of Italy and worldwide. Long targeted legislative initiatives at national and European level tend to promote recovery actions by combining the protection of natural resources with the economic regeneration of contamination affected areas. It is now particularly necessary to develop and promote in situ remediation technologies, directly in the areas to be reclaimed, such as groundwater or contaminated soil. In situ remediation technologies, which avoid the handling and transfer of large material amounts, are therefore less invasive than traditional dig / dump or pump and treat technologies. To be effectively applied, in situ remediation technologies must be based on a thorough knowledge of the conditions that determine the contaminants spread and diffusion in the site: for that reason these technologies are also called “knowledge intensive” as opposed to the traditional ones called “waste and energy intensive”.
Bioremediation of contaminated aquifers
Bioremediation of contaminated sites represents the main European need demanding immediate action. Particular attention is given to in situ bioremediation processes acting directly on the contamination plume and/or source. Among different contaminants, chlorinated compounds, aromatic solvents (BTEX), pesticides and recently human and veterinary pharmaceuticals are an important source of soil and water contamination. Particular attention is paid to the definition of the biodegradation kinetics (microcosm studies, field test) as well as to the identification/quantification of involved microorganisms. Treatability studies, which require a deep knowledge of the involved mechanisms, employ advanced biomolecular tools allowing the monitoring of the microbial degrading populations using in situ hybridization techniques as well as quantitative PCR.
Innovative chemical-physical technologies (AOT, Advanced Oxidation Technologies) based on the use of hydroxyl radicals, able to oxidise a wide variety of contaminants, are needful when the remediation process require a relatively short cure time or when the application of alternative biotechnological strategies is troublesome. In particular, the processes based on the use of UV rays and H2O2 are suitable for treating groundwater because the good water penetrability (UV treatment) or because commonly considered as environmental friendly techniques (H2O2 treatment). The technical and economic feasibility of the above described processes has been proved in recent experiences carried out at IRSA.
Bioremediation of soil contaminated by a wide range of pollutants may be faced by environmentally friendly and cost-effective technologies such as landfarming and biopiles. The application of such methodologies requires preliminary laboratory and field tests assessing the feasibility of remediation and evaluating the potential interactions of contaminants. A landfarming process has been simulated at IRSA to study the remediation of a site contaminated by high molecular weight hydrocarbons and Cr(III). Results showed that aerobic oxidation of hydrocarbons, sustained by indigenous bacteria and enhanced by the addition of amendments, led to residual concentrations below the more stringent limits imposed by legislation. Moreover, taking into account that potential changes of chromium speciation in soil matrices might increase its mobility and bioavailability, it was also assessed that the applied landfarming procedures had no effects on the mobilization of chromium, that remained in its stable form of Cr(III).