Sometimes the simplest discoveries can also be the most profound. That’s certainly the case with a promising new technology being pioneered by Syncrude that uses petroleum coke to treat and de-toxify tailings water.
As a young engineer working with Syncrude’s water recycling systems, Warren Zubot understood that one of the company’s key long-term water management challenges would be the ability to treat tailings water and, ultimately, return some of that water safely to the Athabasca River. Without this ability, the amount of water contained on site would become unsustainable.
The “eureka moment” for Warren came out of a graduate course he had taken in water treatment that dealt with the role activated carbon plays in filtering out contaminants, including through such basic devices as home water filters. Warren asked himself: could petroleum coke, an abundant byproduct of Syncrude’s upgrading process and a material that is almost pure carbon, be used to similarly filter out toxic contaminants in tailings water?
That particular mental light bulb lit up in 2006. It led to several years of laboratory study, followed by an initial field pilot project at Syncrude’s Mildred Lake site, starting in 2012. The research results were very encouraging and paved the way for the next big step—a larger-scale pilot plant, set to begin in 2018, that could eventually lead to commercial implementation of the technology.
“To naturally detoxify tailings water is a slow process, but what takes Mother Nature several years to do, this coke technology does more or less instantaneously.” – Warren Zubot, Syncrude
Just as a home water filter absorbs chemicals present in drinking water, the research to date has shown that petroleum coke can filter out suspended solids and absorb organics like naphthenic acids, the major components in tailings water that make it toxic to aquatic life. The water treated in this way is clear, clean and can support fish species such as rainbow trout.
The technology could play a critical role accelerating the rate of tailings reclamation—a key environmental challenge for the oil sands industry.
“As we find new and better ways to separate more water from tailings, we also need to find ways to manage that liberated water,” says Warren. “Syncrude is assessing ways to use it as process water to reduce freshwater withdrawals from the river, but ultimately we need to be able to return water to the environment.”
Tailings water will never be directly returned to the river, stresses Warren; it must first be treated to ensure it is safe and clean. Regulatory approval also must be obtained. “To naturally detoxify tailings water is a slow process”, he adds, “but what takes Mother Nature several years to do, this coke technology does more or less instantaneously.”
The technology has two inherent advantages, says Warren. The first is its relative simplicity. “In some ways, there is actually no new technology here,” he explains. “Humans have long known about carbon adsorption and filtration. We’re just using it in a novel way.”
The second advantage is that it utilizes a by-product that currently has little value, but is in plentiful supply; for every barrel of oil Syncrude produces, it generates about 20 kilograms of petroleum coke.
The next stage of research, also at Mildred Lake, is a step-change in scale; the pilot plant will encompass an area 5 football fields long by 1.5 football fields wide. The goal is to confirm previous learnings, to improve the process and inform water treatment practices.
The technology is specific to Syncrude as it is the only company to use fluid cokers. But the research findings are being shared with all COSIA members and its potential success would have industry-wide significance because it would provide a venue to develop water treatment criteria and demonstrate water can be safely returned to the environment.
“This would be the first time in the industry’s 50-year history that a company was able to return treated tailings water to the river,” says John Brogly, COSIA Director, Water and Tailings. “That’s significant because it’s something everyone will eventually have to do.”
The ability to return water, he adds, could also help address another common industry challenge, by helping to relieve salt buildup in mined and recycled water to speed up site reclamation.
For Warren, meanwhile, the slow-but-steady progress from an initial concept towards a potentially transformative technology is a reminder of why he became an engineer.
“What drives a project like this is the desire to improve our environmental performance,” he says. “It takes effort, time and patience. But ultimately, one hopes good ideas prevail.”
Contributors
Warren Zubot, M.Sc., P.Eng., Senior Engineering Associate at Syncrude Canada Ltd.
John Brogly, P.Eng, is the Director of COSIA’s Water and Tailings EPAs.