Soil and groundwater at many existing and former industrial areas and disposal sites is contaminated by petroleum hydrocarbons that were released into the environment. Among those petroleum hydrocarbons, fuel oil is more difficult to treat compared to gasoline and diesel fuel due to its characteristics of low volatility, low biodegradability, and low mobility. Thus, a combination of several different treatment technologies is required to remediate fuel oil contaminated soil or groundwater. The objective of this study was to assess the potential of applying Fenton-like oxidation process to remediate fuel-oil contaminated soils. The following tasks were performed in this study: (1) determination of the optimal oxidation conditions, (2) evaluation of the efficiency of chemical by Fenton-like process after the pretreatment of surfactant flushing, and (3) evaluation of the stability of H2O2 by the addition of potassium dihydrogen phosphate (KH2PO4). Total petroleum hydrocarbons (TPH) in soil were analyzed to determine the effectiveness of the oxidation treatment. Results from this study show that the highest TPH removal efficiency (84.8%) was obtained for soils containing 3%(w/w) of fuel oil when 3% of H2O2 was applied followed by 0.05% of H2O2 with 56.7% of TPH removal. Results also show that approximately 69.1% of TPH removal was detected with soils containing 5%(w/w) of fuel oil when 6% of H2O2 was applied followed by 3% of H2O2 with 56.7% of TPH removal and 0.05% of H2O2 with 32.6% of TPH removal. Results also indicate that Fenton-like process has much higher oxidation efficiency than using H2O2 alone. The oxidation efficiency was significantly affected when the contaminated soils were pretreated with surfactant. Results reveal that the maximum allowable surfactant addition was approximately 0.7% (w/w) for soils containing 0.5% (w/w) of fuel oil when 6% of H2O2 was applied. Addition of 2.2 mM of potassium dihydrogen phosphate influence could increase the stability of H2O2, but caused the decrease in the efficiency of TPH removal. During the Fenton-like reaction, pH values were close to 6 to 7. The neutral to slightly acidic conditions caused the decreased dissolution rate of iron minerals. This would also cause the decreased production of hydroxyl radicals from the surface of iron minerals. Results from the byproduct analysis show that the oxidation potential of Fenton-like process is not strong enough to completely destroy the fuel oil to non-toxic end products. The oxidation process produced byproducts containing carboxyl groups with molecular weights similar to their parent compounds.

Sediments are transported by the flowing water then build up on the bottom of water bodies as the materials settle. Contaminated sediments are composed of soils, sand, organic matters, and other minerals that accumulate on the bottom of water bodies and contain toxic or hazardous materials at levels that may adversely affect human health or the environment. The contaminated deposits can be decomposed and released into liquid phase by dramatic changes on environmental conditions. However, the contaminated deposits have a potential of causing changes of nature water system, especially for aquatic livings. Sediments contaminated by light non-aqueous-phase liquids (e.g., fuel oil) and heavy metal are prevalent and of a great concern. The major advantage of Fenton-like oxidation process is that the reagent components are safe to handle and environmentally benign. However, protective enclosure of contaminants with aged sediment matrices and the hydrophobic nature of contaminants limit their accessibility to treatment agents; these obstacles prevent treatment efforts from widespread successes. The interactions of hydrophobic contaminants with the soil matrix in various ways often limit contaminant availability for remediation. In order to overcome this limitation and increase contact, a novel extraction technique that utilized oxidation agent and elevated pressure in consecutive cycles of compression and decompression was developed and applied to soil slurry in the presence of chelating or oxidation agent. The objective of this study was to design a pressure-cycling system that integrates the oxidation agent. This system has the following advantages over traditional chemical treatment: (1) increased process speed, (2) lower operating costs, and (3) the transition metal elements can catalyze the oxidized pollutants. In this study, fuel oil was selected as the target compounds to evaluate the effectiveness of pressure-cycling system on the treatment of fuel oil contaminated sediment. The oxidizing agent used in this study was H2O2. The operating parameters included system pressure, pressure cycles, oxidizing agent concentration, and reaction time. Results show that approximately 38% of TPH was removed after 120 min of reaction with Fenton-like oxidation without pressurization. However, the removal efficiency increased to 47% under the pressure of 10 bar. Thus, pressure-assisted oxidation system is able to accelerate the oxidation reaction, and cause the remove the removal of TPH more effectively. To enhance TPH removal efficiency effectively and reduce the oxidant amount used, water flushing combined with pressure-assisted system as a pretreatment process was applied. Results show that TPH removal efficiency can be significantly enhanced and the amount of oxidant usage can be reduced when the pressurized water flushing was applied before the oxidation process.