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Tailings ponds in Canada’s oil sands development area are a focus for environmentalists and regulators, requiring new technology and regulations to reduce fluid tailings and reclaim them.
Developing Canada’s oil sands deposits, which constitute the world’s third-largest proven reserves of crude oil, is a challenging process that requires advanced technology and continuous improvement. Unlike light crude, bitumen has low gravity and high viscosity, which means that it does not flow at ambient temperatures – in fact it ranges in consistency from thick molasses to hard rubber.
Operators use two main methods for extracting the bitumen from the ground – surface mining and in situ extraction. In surface mining, the bitumen, which is close to the surface, is mined with shovels and trucks, then taken to a facility where the oil is separated from the sand and clay through a water-assisted process.
About 80% of the resource, though, is too deep to mine and is extracted in situ through a steam-assisted process. The bitumen is softened by injecting steam into the ground, and the steam-bitumen emulsion is then lifted to the surface for processing.
Surface facilities that process the emulsion are, in essence, water-treatment facilities that separate the oil from the water and then clean the produced water to high standards in order to turn it into steam for injection back into the ground.
Stringent water use regulations
The oil sands industry is subject to stringent environmental scrutiny, with government, regulatory bodies, academia, and industry groups working together to minimize the environmental impact of such operations and return the disturbed areas back to their natural state at an operation’s end of life.
Water use and recycling are the focus of both regulators and industry since water is the solvent of choice for the mining and in situ processes. Current mining operations recycle 80% to 90% of the produced water, while in situ operations recycle between 90% and 95%.
Alberta’s Energy Resources Conservation Board (ERCB) sets target rates on individual projects to drive continuous improvement in water recycling technology. Water lost to the process needs to be replenished, but new regulations require that operators minimize the use of freshwater sources for makeup.
As a result, new projects have focused on using saline aquifers, groundwater, or treated produced water from other sources in their operations. Tailings ponds, which are the man-made ponds where mining operators separate the water from the leftover mixture of water, sand, fine clay, and residual bitumen produced during the extraction process, have become the focus of a number of technology projects and new regulations.
The ERCB’s Directive 74 establishes new rules for accelerating the reduction of fluid tailings and reclamation of tailings ponds. Suncor Energy Inc., the first Canadian company to begin developing Canadian oil sands, has developed a new tailings management approach, called the TRO process, which dries the tailings into a material that is solid enough to be reclaimed in less time than available technologies require.
This technology has enabled Suncor to cancel plans for five additional tailings ponds and project the elimination of all but one of the eight existing ponds at its Alberta mine site. The process will cut the standard life cycle for tailings ponds – from initial land disturbance to reclaimable surface – by two-thirds in about 10 years.
In 2010, Suncor became the first oil sands company to achieve surface reclamation of a decommissioned tailings pond – now known as the Wapisiw Lookout – and is transforming it into a revegetated mix of forest and small wetland that supports a variety of plants and wildlife.
Responding to water-use challenges
Industry associations, government-funded research associations, operators, and suppliers of technology to the oil sands also have taken on the challenge of developing advanced technologies to minimize water use, accelerate tailings ponds reclamation, improve recycle rates, and ultimately reach the coveted zero-liquid discharge.
For example, Alberta Innovates, a government-funded research center, is collaborating with companies like Suncor and GE on a technology program that is finding innovative ways to recycle water. A collaborative network of oil sands operators called the Oil Sands Leadership Initiative (OSLI), which is comprised of six energy companies, also is funding and piloting specific programs to reduce intensity of water use without environmental burden-shifting.
One such program is OSLI’s Regional Water Management Solutions initiative, which aims to produce a more economically attractive solution with lower environmental impact and a high degree of security of make-up water supply and tailings water disposal.
It also intends to reduce industry’s current water use and increase overall water recycling by expanding water reuse across mining and in situ operations throughout the watershed. (A video about GE’s work with OSLI on a pilot project determining the feasibility of recycling tailings water to generate steam at in situ facilities is available at osli.ca/media-resources/tailings-treatment.)
Operators like Suncor Energy work directly with technology providers like GE to reach their environmental stewardship goals. In 2010, Suncor and GE embarked on a number of innovative technology-development programs aiming to increase the water treatment reliability of in situ facilities.
As a member of OSLI, Suncor worked with GE’s Heavy Oil Center in Calgary and its Water and Process Technologies business to determine the feasibility of using tailings water to generate steam at in situ facilities.
Suncor’s Firebag and MacKay River in situ sites already are implementing this sustainability breakthrough, which incorporates GE’s ultrafiltration, reverse osmosis, and ZeeWeed 500 reinforced hollow-fiber membrane technologies. The sites use recycled water from a closed system for steam generation with minimal makeup.
For example, at the other end of oil sands production is refining, and Suncor made use of GE’s skid-mounted reverse-osmosis system to furnish its 135,000 b/d Edmonton refinery with recycled wastewater from the local Gold Bar treatment plant.
The arrangement, which supplies the refinery with half of its water, meant that Suncor could avoid drawing 56.5 MMcf of water from the North Saskatchewan River for the refinery’s operations. A full-scale pilot plant, based on GE’s membrane technology, established the parameters for the final wastewater treatment plant design. This early involvement also helped identify potential downstream issues that could impact treatment.
With GE’s assistance, Suncor and the city of Edmonton enjoy a responsibly operated facility that contributes to industrial and community growth.