Combined Application of Ozone and Hydrogen Peroxide to Degrade Diesel Contaminants in Soil and Groundwater

Environmental pollution has been a major concern in recent times, and soil and groundwater pollution are areas which have received particular focus. This has led to the development of various remediation techniques such as excavation, soil vapor extraction, bioremediation, chemical oxidation, and so on. Among all remediation techniques, chemical oxidation has been proven to be the most effective and feasible technique around the world. In this study, various combinations of ozone and hydrogen peroxide were used to treat diesel-contaminated soil and groundwater in an experimental setup. Experimental soil and groundwater were prepared with properties similar to the contaminated soil. An ozone generator and a pump injection system were deployed for combining ozone and hydrogen peroxide. Five different experiment batches were prepared based on the hydrogen peroxide concentration and its ratio to the soil. The diesel concentration in the water dropped from 300 mg/L to 7 mg/L in the first hour of treatment, which dropped below the detection limit (0.01 mg/L) thereafter. Similarly, 63.9% degradation was achieved with the combined sparging of ozone and hydrogen peroxide in the soil. Ozone combined with 7% hydrogen peroxide was the most promising combination for removing the contaminants. In addition, this research explored the hydroxyl radical conversion rate of ozone and the perozone, the difference in order of magnitude is greater than one which shows that the perozone has better oxidation capacity than ozone only. The findings of this study show that combining ozone with hydrogen peroxide is a competent and feasible onsite remediation method for diesel contaminants in soil and groundwater. Thus, this method can be applied in local gas stations, accidental spillage sites, and small-scale refineries for onsite treatment in a cost-effective and technically sound way within a short time span.

Determination of concentration-dependent dispersion of propane in vapor extraction of heavy oil

Vapex (vapor extraction) is a solvent-based non-thermal in-situ heavy oil recovery process. In Vapex process, a vaporized hydrocarbon solvent is injected into an upper horizontal well where the solvent mixes with the heavy oil and reduces its viscosity. The diluted oil drains under gravity to a bottom production well. Two mechanisms control the production rates of heavy oil in Vapex: mass transfer of solvent into heavy oil, and gravity drainage. Both are governed by dispersion, which is composed of molecular diffusion, convection, and other mechanisms that enhance mixing in porous medium. The accurate determination of solvent dispersion in Vapex is essential to predict effectively the amount and time scale of oil recovery as well to optimize the field operations. Motivated by limited dispersion data in the literature, a novel technique is developed to determine experimentally the concentration-dependent dispersion coefficient of propane in Vapex process, The technique employs live oil production rates obtained from Vapex experiments at 21ºC and 0.790 MPa. The salient feature of this technique is that it does not impose any functional form on dispersion as a function of concentration, but allows its natural and realistic determination. The technique could be applied to determine other solvents dispersion coefficient used in the in-situ recovery of heavy oil. Propane dispersion coefficient is determined by the minimization of the difference in experimental and calculated cumulative live oil produced. The necessary conditions for the minimum are fundamentally derived, utilizing the theory of optimal control. A computational algorithm is formulated to calculate the propane dispersion function simultaneously with propane-heavy oil interface mass fraction. Physical models of glass beads of different permeabilities (204-51 Darcy) and drainage heights (25-45 cm) were used to conduct the Vapex experiments. The results show that dispersion of propane is a unimodal function of its concentration in heavy oil, and lies in the range, 0.5x10⁻⁵- 7.933x10⁻⁵ m²/s. Convectional mixing is promoted by higher model drainage heights and lower permeability. Finally, propane dispersion is correlated as a function of propane mass fraction in heavy oil and the packed medium permeability, as well as the drainage height.

Determination of concentration-dependent dispersion of propane in vapor extraction of heavy oil

Vapex (vapor extraction) is a solvent-based non-thermal in-situ heavy oil recovery process. In Vapex process, a vaporized hydrocarbon solvent is injected into an upper horizontal well where the solvent mixes with the heavy oil and reduces its viscosity. The diluted oil drains under gravity to a bottom production well. Two mechanisms control the production rates of heavy oil in Vapex: mass transfer of solvent into heavy oil, and gravity drainage. Both are governed by dispersion, which is composed of molecular diffusion, convection, and other mechanisms that enhance mixing in porous medium. The accurate determination of solvent dispersion in Vapex is essential to predict effectively the amount and time scale of oil recovery as well to optimize the field operations. Motivated by limited dispersion data in the literature, a novel technique is developed to determine experimentally the concentration-dependent dispersion coefficient of propane in Vapex process, The technique employs live oil production rates obtained from Vapex experiments at 21ºC and 0.790 MPa. The salient feature of this technique is that it does not impose any functional form on dispersion as a function of concentration, but allows its natural and realistic determination. The technique could be applied to determine other solvents dispersion coefficient used in the in-situ recovery of heavy oil. Propane dispersion coefficient is determined by the minimization of the difference in experimental and calculated cumulative live oil produced. The necessary conditions for the minimum are fundamentally derived, utilizing the theory of optimal control. A computational algorithm is formulated to calculate the propane dispersion function simultaneously with propane-heavy oil interface mass fraction. Physical models of glass beads of different permeabilities (204-51 Darcy) and drainage heights (25-45 cm) were used to conduct the Vapex experiments. The results show that dispersion of propane is a unimodal function of its concentration in heavy oil, and lies in the range, 0.5x10⁻⁵- 7.933x10⁻⁵ m²/s. Convectional mixing is promoted by higher model drainage heights and lower permeability. Finally, propane dispersion is correlated as a function of propane mass fraction in heavy oil and the packed medium permeability, as well as the drainage height.