Remediation of Flare Pit Soils Using Supercritical Fluid Extraction

Many sites are contaminated with petroleum hydrocarbons (PHCs). In some cases, these PHCs may be biorecalcitrant and therefore the soils contaminated with these PHCs are not amenable to remediation by biological treatment methods. Examples of sites containing biorecalcitrant PHCs are old flare pit sites. Flare pits are earthen pits that were once used for the storage and disposal of natural gas and crude oil wastes. Alberta’s oil patch contains thousands of flare pits that need remediation and reclamation. At some sites, the soils in and around these flare pits are highly contaminated with biorecalcitrant PHCs that current remediation technologies such as bioremediation and, more rarely, composting, may be limited. Remediation of sites containing high concentrations of biorecalcitrant petroleum hydrocarbons (PHCs) is usually performed by means of excavation and landfilling. New, more effective treatment technologies are therefore being investigated to treat these types of soils. Supercritical fluid extraction (SFE) is a potential treatment technology for the remediation of flare pit soils. This research focuses primarily on the use of a laboratory scale SFE system to investigate the extraction of PHCs from contaminated flare pit soils at various temperatures and pressures ranging from 40°C to 80°C and 9 MPa to 19 MPa, respectively. Preliminary experiments using flare pit soils obtained from sites across Canada are currently underway. The effects of pressure, temperature and extraction time on the extraction efficiency of the process will be investigated. It is anticipated that the highest supercritical fluid (SCF) density will yield the best extraction efficiency. Since the flare pit soils under investigation are aged and weathered soils, the effect of longer extraction times on the extraction efficiency will also be studied. The obtained results will allow the identification of optimum conditions for the SFE extraction. These results will provide the necessary information for potentially developing SFE as a fast and effective technology for remediation and decommissioning of flare pits in Alberta and elsewhere in Canada.