Researchers aim to clean up toxic Athabasca water

Northern Alberta is home to some of the fastest-growing bodies of water in the world. Every day roughly two billion litres of water – enough to fill 800 Olympic swimming pools – are added to these lakes, which are already over 11.5 trillion litres in volume.

The largest one, located near Mildred Lake just north of Fort MacMurray, is big enough to meet the water needs of a town of 70,000 people for 50 years.

But none of the artificial lakes are fit for human consumption – they’re filled with water that’s been diverted from the Athabasca River and used to extract bitumen, a viscous, tar-like form of petroleum found in the Athabasca oil sands.

As a result, the water is toxic to humans, fish, birds, and even bacteria. Covering an area of more than 130 square kilometres, these tailings ponds are far from scenic – but they’re the easiest, most efficient way to deal with the toxified water.

“In bitumen processing water is a big, big problem,” said Greg Dechaine, a researcher at the Centre for Oil Sands Innovation at the University of Alberta. Scientists are trying to find better ways to clean up the water and avoid using so much in the first place.

Heavy, viscous fluid

Their advances so far have been modest — water will probably remain a key environmental issue for the oil sands for the foreseeable future, along with the greenhouse gases produced by the energy-intensive extraction process. But their work holds promise for a cleaner future for an industrial project the size of England.

Alberta’s oil sands are made of bitumen — a heavy, viscous fluid that is eventually refined into fossil fuels, mixed up with sand, clay, and water in the ground.

About 20 per cent of the bitumen in the oil sands is close enough to the surface that companies such as Syncrude and Suncor get at it using giant shovels and dump trucks in open pit mines. The remainder is so far underground that it has to be pumped to the surface using steam and suction.

Once the sand is out of the ground, companies use a bitumen extraction process developed by Karl Clark at the University of Alberta in the first half of the 20th century.

Actually, calling it a process might give the wrong impression – essentially, the sand is simply blasted with hot, pressurized water. Dechaine described it as “like taking a plate and running it under the tap and you just basically blast all the bits and pieces off.”

The amount of water required to do this varies based on the origin of the sand. If it comes from an open pit, it takes between two and 4.5 barrels of water to obtain one barrel of bitumen. But if the sand is extracted from deep underground, about one barrel of water total is required.

Once separated from the sand, water, and clay, the bitumen goes on to be processed into usable fossil fuels. The water is recycled until it is saturated with so much hydrocarbons and metals from the sand that it cannot be used anymore. After that, it goes into one of the ever-growing tailings ponds.

A dirty problem

The tailings ponds’ water use “is the equivalent of the use of a city the size of Calgary,” said David Schindler, a professor of ecology at the University of Alberta and a leading water scientist. “Right now, it’s just sitting there indefinitely.”

Schindler sees the oil sands as a threat to the long-term health of the Athabasca River. Taking water from the river when it freezes over in the winter lowers oxygen levels in the water, making it more difficult for fish to respire.

He also said that the tailings ponds may leak into the river and cause health problems for communities downstream, though no reliable statistics are available. He has called for a moratorium on the development of new oil sands extraction plants until more research is done into reducing their environmental impact.

Terra Simieritsch, an oil sands policy analyst at the Pembina Institute, a non-partisan think-tank in Alberta, agrees. Simieritsch said she would like to see a halt on new project approvals “so we allow some time to figure things out a little bit better and have better environmental management in place.”

While the mining continues, some scientists have dedicated their efforts to cleaning up the contaminated waters.

Richard Johnson, a biologist at the University of Essex, has discovered a way of using microbes to breakdown some of the toxic hydrocarbons found in the end-process water — specifically napthenic acids. Johnson treated a naphthenic acid solution with a cocktail of naturally-occurring bacteria, and found that the bacteria will totally metabolize some of the acids into water and carbon dioxide. However, the more complex, branched acid molecules did not breakdown completely.

Strangely, the acids Johnson’s bacteria ate are toxic to the microbes themselves.

“We’ve found in many of our experiments that the acids are toxic to the bacteria as well,” said Johnson. “So, if we add too much of the acid, the bacteria will just all die, and then not eat any of them. So you need to kind of strike the right balance.”

Finding that balance might be a bit of a problem. The microbes exhibited symptoms of toxicity at acid concentrations as low as five milligrams per litre, and naphthenic acid concentrations in tailings ponds can be up to 24 times that. Still, Johnson remains optimistic that microbes will be used to cleanup tailings ponds eventually, though he concedes it might be decades away.

Another approach to making the oil sands more water-friendly is to develop an extraction process that doesn’t require water. Researchers all over the world are exploring different ways of doing this.

Going dry

In a paper published in 2008 in the journal Ultrasonics Sonochemistry, four chemists at the Kurnakov Institute of General and Inorganic Chemistry in Moscow describe using ultrasound on oil sand to extract bitumen from oil sand.

By subjecting a sample of oil sand to sonic waves above 20,000 hertz – a sort of industrial version of the scanners used to determine the sex of a foetus – the Russians were able to shake the bitumen apart from the sand, clay and water in less than an hour.

However, the experiments were on samples of sand less than a half litre in volume, and extracted about 2.5 grams of bitumen from each sampled tested. According to the Canadian Association of Petroleum Producers, the oil sands produce over 1.3 million barrels of bitumen every day, and production is expected to nearly triple by 2025. No tests at that kind of scale have been done.

Non-aqueous extraction methods are also being explored at the University of Alberta. One is the the brainchild of environmental engineer Selma Guigard. Guigard’s method involves “supercritical” carbon dioxide – a heated, pressurized solvent that behaves somewhat like a liquid and somewhat like a gas.

Guigard’s method mixes supercritical carbon dioxide with oil sand and then de-pressurizes the slurry, forcing the bitumen to separate from the rest of the mixture. The carbon dioxide can be recycled indefinitely, and the only water involved in the process is that already naturally mixed with the bitumen, sand and clay.

Once again, though, the technique has yet to be tested at the sort of scale that would let it replace the Clark process in northern Alberta. Guigard has had difficulty obtaining the funding necessary to build a small pilot plant.

Murray Gray, the director of the University of Alberta’s Centre for Oil Sands Innovation, predicts that Guigard’s method won’t be used in industry any time soon because carbon dioxide simply doesn’t mix well enough with bitumen to be viable.

“Nothing that’s been published shows that you can get good dissolution of the bitumen in carbon dioxide,” he said. “Unless someone can lick the solubility problem, it won’t be used.”

Gray’s Centre is doing its own research into non-aqueous extraction using organic solvents like paint thinner. Currently, the Centre is trying to understand the fundamentals of how that might work.

“What we didn’t do was run into the lab with a bunch of pots and pans and start playing around with different solvents and additives,” said Gray. Instead, the Centre is focused on the basic research required to design a practical non-aqueous extraction process. Gray estimates that their method is six years away from being used by industry.

In the meantime, the tailings ponds continue to present a serious hazard to wildlife in northern Alberta. The Canadian Association of Petroleum Producers encourages mine operators to use “cannons, scarecrows, decoy predators and radar/laser deterrent systems,” but they don’t always work.

In April 2008 about 500 migrating ducks died when they landed on a Syncrude tailings pond, and according to the Pembina Institute about 100 wading birds mistake the ponds for mudflats every year and become covered in oil as a result.

As the tailings ponds continue to grow, environmentalists like Simieritsch and Schindler are pessimistic about the future of the Athabasca River. Schindler said he saw no new methods on the horizon that could operate at the needed scale.

“If they can go ahead with these non-aqueous bitumen extractions and they’re found to be safe, then that’s great,” said Simieritsch. “But, you know, we still see that current [mining] projects are going ahead with large volumes of water use.”