Water quality issues associated with implementation of composite tailings (CT) technology for managing oil sands tailings

摘要

In the oil sands industry, Composite Tails (CT) is an attractive tailings management approach. In the CT process, the fines or clay fraction of extraction tailings are mixed with the coarse sand fractions, such that, with the addition of a coagulant aid, a non-segregating deposit is produced. Various coagulant aids have been tested and have been shown to destabilize suspensions of fines and clays. After treatment, the fines aggregate and with the stress or load of the coarse sand fraction will dewater, with the fines remaining trapped with the coarse fraction, and particle-free water being released. The rate and degree of water release determine when the resulting deposit can be classed as a solid or dry landscape for reclamation. The coagulation of the clays can be accomplished with a variety of chemicals, both organic and inorganic, that initiate clay destabilization and affect water quality. Depending on the coagulant aid, changes in pH, salinity, cation and anion levels, buffering capacity and toxicity have been observed. The impacts on water quality with the use of several chemical treatments are described and potential influence of the CT release waters on operational aspects and reclamation issues are discussed.