Persulfate Ex-Situ Chemical Oxidation of Petroleum Hydrocarbon Contamination in Soil under Relatively Dry Conditions
Chemical oxidation is a technology used for the remediation of contamination in various media and under different conditions. It is commonly used on in-situ treatments for the remediation of ground or ground water contaminations. This application is limited to sites presenting appropriate subsurface conditions and allowing sufficient water circulation. The ex-situ application of chemical oxidation on soil contamination is not as common because the infrastructure needed for such a treatment is considerable due to the slurry conditions this treatment is usually set up under. The laboratory study presented in this report is an investigation of the persulfate chemical oxidation of TPH contaminated soil under relatively dry conditions. The limited amount of liquids added was based on the handleability of the soil during the treatment. This limitation was applied to develop a remediation technology which would allow exsitu treatment of contaminated soil to be undertaken without the need for large equipment mobilisation as the treatment could be set up as soil piles in the same manner applied to bioremediation. The variation in different parameters was studied by setting up a series of treatments presenting various conditions using two different media (spiked garden soil and spiked sand). The activation route and the addition of methanol as a solvent to the system were the main variable parameters. The results of the research proved the importance of the stoichiometry applied to the amounts of reagent added under such unfavourable conditions. The reduction of the liquid amount in the chemical oxidation system is a strong limitation which implies that no other limitation should be applied to the system to allow the oxidation to be effective. Under the applied conditions, the remediation of the contamination was unsatisfactory for the application to a large scale remediation project. Further investigation is needed to optimise the stoichiometry of the reagents and increase the efficiency of the treatment to permit an up- scaling of the method. A rapid and simple method for the measurement of the persulfate concentration in the media was developed to permit the monitoring of the oxidant in the treatments. The method is based on a published method for the measurement of persulfate concentration in aqueous media (Liang, Huang et al. 2008).