Water plays a central role in open pit mining of Canadian oil sands (Figure 1). Vast quantities of water from the Athabasca River are used and recycled for processes such as extracting bitumen (heavy, thick form of crude oil) from sand. Bitumen extraction and upgrading processes generate wastewater (known as process-a ected water) that contains elevated levels of constituents that are toxic to aquatic organisms including: naphthenic acids (NAs), salts, polycyclic aromatic compounds, metals and others. Since process-affected water is toxic to aquatic organisms,it cannot be safely discharged into the Athabasca River andneeds to be temporarily stored on-site in previously mined pits or tailings ponds. Once mining operations have ceased, the site will be reclaimed using dry and wet landscape strategies. Wet strategies include placement of process-affected water and/or tailings to create shallow wetlands in some areas and large end pit lakes in previously mined pits. Eventually, this network of reclaimed wetlands and lakes will be connected to the watershed. Understanding the chemical nature and e ects of NAs is one of the greatest challenges for wastewater management in the oil sands. There are concerns that NAs in process-a ected water could hinder the environmental health of aquatic reclamation options or escape into the Athabasca River. Insu cient past monitoring by outdated and inaccurate analytical methods has provided little valuable data to make scienti c evaluations of safety and risk. The multi-disciplinary team brought together for this research, which was funded in part by Canadian Water Network, developed and executed a wide range of projects to address knowledge gaps in the chemistry of NAs and the fate and the effects of these compounds in aquatic environments. Projects were conducted under laboratory-based conditions and/or field-based conditions to address environmental issues associated with wastewater storage (e.g. oil sands tailings ponds) or the use of wastewater in reclamation (e.g. experimental wetlands and ponds constructed in 1980s and 1990s).
The research conducted covers a broad range of questions relevant to wastewater management in the oil sands from environmental assessment to remediation. The following examples highlight some of the studies conducted, the findings and the significance of these findings for wastewater management and regulatory agencies.