Design and optimization of surfactant based enhanced remediation of bunker C fuel oil contaminated soil

Soil pollution, particularly by petroleum compounds is a very important global issue. It is typically a result of improper storage and disposal, historic careless spills, accidental spills, and leaks from tanks. This environmental damage can result in wide spread groundwater and surface water contamination, and limit soil use for agricultural purposes. There are a large number of brownfield sites across Canada. These are sites that have been previously used for industrial and commercial activities and have been contaminated with hazardous wastes. Newfoundland and Labrador (NL) in particular, has numerous sites due to a legacy of fuel oil use for power generation at abandoned, old and emerging mining fields. Data from the federal contaminated site inventory indicate that on federal owned sites in NL, there are over 3000 m³ of oil-contaminated soil. It has therefore become necessary to develop remediation technologies that are economically and technically feasible, environmentally friendly, fast, and applicable in a wide range of physical settings. A wide range of technologies have been developed over the past few decades for the remediation of contaminated sites. Some of these processes have been found to be successful in removing only a specific group of contaminants from the soil. As a result, combinations of different approaches are usually adopted for more effective remediation thereby leading to more expensive remedial operations. Surfactant-enhanced remediation technology, otherwise known as soil washing has proven to be an effective method to remove a mixture of contaminants such as heavy metals, petroleum compounds, volatile organic compounds, pesticides and herbicides as well as other hazardous and non-degradable substances from contaminated soils. Surfactant remediation relies on the ability of surfactant formulations to remove both organic and inorganic contaminants from soil and sediments by desorbing them from the solid to liquid phase. The technology removes contaminants via two mechanisms; one occurs below the Critical micelle concentration (CMC) of the surfactants known as mobilization mechanism, and the other above the CMC known as solubilization mechanism. However, this technology has not been widely reported for the remediation of Bunker C fuel oil, a complex and recalcitrant petroleum compound that is persistent in the environment and extensively reported to be resistant to chemical and biological degradation, and therefore difficult to remediate. This research presents an assessment of the performance of soil washing technology for the remediation of Bunker C contaminated oil from weathered contaminated soil using patented surfactant formulations. Weathered soil are known to be more difficult to remediate than freshly contaminated soil hence, the study used weathered soil in order to be certain of the effects of soil washing on Bunker C removal. Specific research objectives include: (1) determining the micellar properties (Surface Tension and CMC) of the patented surfactants, (2) development of a reliable analytical method for the analysis of (heavy) petroleum hydrocarbons in soil, (3) evaluation of the parameters that govern the implementation of soil washing and an assessment of their effects on the washing of weathered Bunker C oil from contaminated soil at surfactants concentrations below the CMC (mobilization mechanism) using the multivariate experimental and statistical approach, (4) determination of the optimum conditions (optimization) for the removal of Bunker C oil with the tested surfactants. The research, in the course of analysing the Total Petroleum Hydrocarbon in the soil using the Canada-Wide Standard (CWS) for Petroleum Hydrocarbon in soil is used for the analysis of petroleum hydrocarbon compounds found considerable variability and inconsistencies in the results. This could be due, in part, to the different gas chromatography (GC) conditions, soil properties, as well as and other steps involved in the method. These differences impacts the determination of the effectiveness of remediation at hydrocarbon-contaminated sites. The thesis therefore, developed validated the analytical method for the quantitative analysis of TPH in (contaminated) soil. The newly developed method was successfully applied for a faster and more reliable analysis of TPH of Bunker C oil in contaminated soil. It is expected that this research will lay a road map for further studies on the application, optimization and development of a treatment system protocol for the use of soil washing for Bunker C remediation. It should be noted that although Bunker C is the contaminant, the hydrocarbon composition of Bunker C makes it a good surrogate for other heavy oils.

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