Process water treatment in Canada’s oil sands industry: I. Target pollutants and treatment objectives

Abstract

Process water treatment has become a critical issue for Canada's oil sands industry. Continuous recycling of tailings pond water (TPW) has contributed to a decline in water quality that has consequences for bitumen recovery, water consumption, and reclamation efforts. Potential roles for water treatment were assessed through a review of process water quality and toxicity data from two long-term oil sands operations. Target pollutants were identified according to exceedances of environmental and industrial water quality guidelines. From 1980 to 2001, the salinity of TPW increased at a rate of 75 mg/L per year. Recent increases in hardness, sulphate, chloride, and ammonia have raised concerns over scaling and corrosion. Naphthenic acids released during bitumen extraction are the primary source of toxicity in TPW. Biodegradation of naphthenic acids has been demonstrated in pond experiments; however, recalcitrant compounds may contribute to chronic toxicity in reclaimed environments. Water treatment objectives established in this review provide benchmarks for the selection of candidate water treatment technologies.

Oil sands development contributes elements toxic at low concentrations to the Athabasca River and its tributaries

“…In addition to watershed disturbance, the process of upgrading bitumen to synthetic crude oil involves coking, coke combustion, and production of wastes and fly ash that contain PPE (15)(16)(17). Environment Canada's National Pollutant Release Inventory shows that upgrading is a substantial and increasing source of PPE to air.…”

Impact of petroleum coke characteristics on the adsorption of the organic fractions from oil sands process-affected water

“…While studying the effect of inorganic anions on vanadium leaching from PC in water which contained sulfur, chloride, and bicarbonate ions, Puttaswamy and Liber (2012) showed that bicarbonate ions increased the release of vanadium from PC. Since the concentration of bicarbonate ions in OSPW is very high (775-950 mg/L) (Allen 2008a), this may also promote leaching of vanadium from PC upon its contact with OSPW. In addition, the organic fraction of OSPW contains large variety of compounds which could stabilize vanadium in the aqueous phase and increase its equilibrium concentration as compared to Milli-Q water.…”

“…As a result, it becomes corrosive and highly toxic due to high concentrations of salts and refractory organic compounds such as naphthenic acids (NAs) . The storage of OSPW has raised several environmental concerns, including the presence of trace concentrations of NAs in surface waters around the oil sands operation facilities due to their leaching from tailings ponds (Allen 2008a).…”

Assessing the sublethal effects of in‐river concentrations of parameters contributing to cumulative effects in the athabasca river basin using a fathead minnow bioassay

“…This OSPW contains several inorganic and organic constituents, some of which have been shown to be acutely toxic to aquatic life. Some of these constituents include high levels of salinity, sulphate, ammonia, conductivity, and naphthenic acids [6]. There is the potential for some of these components to make their way into the Athabasca River through seepage and air deposition [7].…”