Evaluation of high density oil dissolution in saturated porous media for petroleum hydrocarbons contaminated sites

To better understand the environmental behaviour of fuel oil used in the power industry ( Fuel oil no.6), in case of accidental spilling in groundwater, a two-step experimental study with laboratory batch equilibrations and with a two-dimensional physical model of aquifer was carried-out. Preliminary characterisation of the the oil mixture included determination of boiling points distribution of homologue class of hidrocarbons, followed by determination of mass transfer coefficients at the water-oil iterface of relevant BTX, PAH and TPH substrates. Effective solubilities of SWSCs (Slightly water soluble compounds) were obtained and an empirical equation for evaluating partition coefficients of SWSCs compounds of environmental concern in the commercial Fuel oil no.6 samples was set-up and validated. In the second part of the investigation a physical model of an homogeneous sand aquifer was set up and, by following transport phenomena from oil pools (0.5-1 m long), laying on the water table of the saturated porous media, the influence of mass transfer and dissolution rates of specific compounds (benzene, toluene, naphtalene) were evaluated by continuous sampling of groundwater from the model at fixed contact times (7 and 28 days). Experimental data were correlated by assuming an analytical model for contaminants dissolution in the oil-water system and mass transfer rates for different contaminants were evaluated and compared with the experimental figures obtained after determination of the effluent concentration from the model. A practical relationship between dissolution time of contaminants and filtration velocity of groundwater, as a function of the extension of the pool and water-oil partition coefficient, was also obtained.