Long-term column leaching study of centrifuged oil sands fine tailings

摘要

In 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.