Redox Biogeochemistry and Oxygen Consumption Rates Associated with Oil Sands Fluid Fine Tailings (FFT)

English Abstract:

The first pilot scale end pit lake (EPL) is now being assessed in Canada’s oil sands region, using water capped tailings technology (WCTT) for fluid fine tailings (FFT) management. Oil sands tailings are non-cohesive, fine-grained, materials that host highly active and diverse microbial communities in addition to substantive organic carbon, Fe and S constituents capable of consuming oxygen. The key to the viability of EPL as a reclamation strategy will be the evolution of the water chemistry such that the EPL is capable of supporting aquatic biota. Critical to achieving this goal is the extent and evolution of oxygen demand, both biological (BOD) and chemical (COD) associated with the subaqueously deposited tailings layer over time. The objectives for this study are to: 1) determine in-situ oxygen consumption rates in the oxic layer and associated with FFT transferred up into the oxic layer at 3 sites over ice off and annual time frames and 2) determine concentrations of redox reactive constituents (SO₄^2-, CH₄, CH₂O, Fe³⁺) to establish the impact that each has in the oxygen consumption of the water column., As a lead to in situ determination starting in 2015, results from laboratory based, sterile (abiotic reactions only) and biotic (endemic microbial activity possible) mesocosm experiments evaluating the rates of oxygen consumption using oil sands tailings and process water will be presented.