EXPERIMENTAL STUDY OF DISSOLVED MtBE REMOVAL FROM A SATURATED MEDIA BY CHEMICAL OXIDATION

In the last decades groundwater contamination by MtBE due to fuel spills or leakage from fuel underground storage tanks has become a highly sensitive environmental issue. Among all the in-situ groundwater remediation treatments, the In-Situ Chemical Oxidation (ISCO) is remarkable for its effectiveness, ease of handling and low associated costs. Since the efficiency of In-Situ Chemical Oxidation strongly relies on site-specific conditions, which affect the oxidant delivery and the geochemical reactions within the subsoil, experimental tests at intermediate scale may help to evaluate the effectiveness of the technology at conditions similar to the field ones, prior of its implementation on site. In this paper experimental tests on MtBE oxidation with Fenton reagents are presented and discussed. Tests were carried out in a laboratory apparatus consisting both of beakers (to carry out preliminary batch tests) and of a steel tank that replicates, at a smaller scale, an In-Situ Chemical Oxidation system applied to a saturated porous media (intermediate scale test). The results of oxidation tests revealed a general effectiveness of In-Situ Chemical Oxidation at removing MtBE from water, especially in the bench scale tests where MtBE residual concentration were much lower than the ones reached at the intermediate scale test. In this latter, however, the highest decrease of MtBE concentrations was recorded where the contaminated pore water was directly impacted by the injection of oxidants, thus confirming that the delivery of the oxidant solution through the porous media plays an important role in the overall removal efficiency of In-Situ Chemical Oxidation. Kinetic tests also showed that, at the investigated experimental conditions, MtBE undergoes to a degradation process which involved the formation of oxidized by-products (TBF, TBA) and the final transformation into acetone, the most abundant and persistent by-product.