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TitleLong-term column leaching study of centrifuged oil sands fine tailings
AuthorUtting, NORCID logo
SourceEnvironmental Earth Sciences vol. 80, 462, 2021 p. 1-21,
Alt SeriesNatural Resources Canada, Contribution Series 20210290
Mediaon-line; digital
File formatpdf
NTS82; 83; 84; 72E; 72L; 72M; 73D; 73E; 73L; 73M; 74D; 74E; 74L; 74M
Lat/Long WENS-120.0000 -110.0000 60.0000 49.0000
Subjectsfossil fuels; Science and Technology; oil sands; reclamation; tailings; tailings analyses; water quality; leaching
Illustrationsphotographs; tables; photomicrographs; histograms; plots
ProgramCanmetENERGY - Devon Director, Upstream and Environmental Impacts - Upstream and Environmental Impacts Operations
Released2021 07 04
AbstractIn northeastern Alberta, oil sands deposits are mined and processed to extract bitumen, which is then converted to synthetic crude oil, a waste stream of this extraction process is fluid fine tailings. Seepage and leaching from these tailings have the potential to negatively impact surface and groundwater quality. This research focuses on improving and understanding dissolved ions that may seep from treated oil sands fine tailings using long-term column leaching experiments. Concentrations of dissolved ions in water leaching from the columns were measured over nineteen months. For most ions, changes in concentration were as expected, generally decreasing once a peak concentration was reached soon after the start of the experiment. However, some ion concentrations, particularly those of magnesium and strontium, increased late in the experiment. When at maximum concentration, for two to three pore volumes, the leachate (or eluant) from the columns exceeded Alberta Tier 1 guidelines (groundwater remediation guidelines for sodium, arsenic and zinc). The Tier 1 guideline for sodium is 200 mg/L and was exceeded during discharge from all four columns for at least some part of the experiment. Leachate also exceeded Canadian Council of Ministers of the Environment water quality guidelines for protection of aquatic life for manganese and occasionally for cadmium, copper, lead and nickel.
Summary(Plain Language Summary, not published)
In northeastern Alberta, oil sand deposits are mined and processed to extract bitumen. The extraction leaves large areas of land that will need to be reclaimed following mining. Waste produced by the oil extraction process include fluid tailings, which, even with treatment, can take many years to settle to be strong enough to support vegetation. Without treatment, the solids do not settle beyond a still-fluid state. Additionally, the tailings contain contains trace metal contaminants, elevated total dissolved solids (TDS) and dissolved organic such as naphthenic acids. This research focuses on improving our understanding of what elements will leach from oil sands tailings over time. The study presented in this paper presents a long terms column leaching test of dewatered fine oil sands tailings. For most elements measured the concentration leaching decreases over time, however the concentration of some elements increase late in the experiment. This may be related to degradation of polymer used to treat tailings.

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