An investigation that began as a straightforward chemical analysis of oil sands tailings has yielded a patented method for turning this tainted material into a rich biological habitat.
It was not exactly what University of Windsor biogeochemistry professor Chris Weisener had in mind when he first tried out the idea of employing gamma irradiation (GI) to this waste product. The original goal was simply to get rid of whatever living specimens remained in those samples in order to measure the oxygen demand of the sediments, a key factor that could limit the success of soil reclamation efforts.
However, what he and UWindsor biology professor Jan Ciborowski found was that the GI treatment dramatically reduced the levels of organic pollutants — primarily naphthenic acids — concentrated in the tailings by the oil sand extraction process. Irradiation eliminated as much as 95 percent of those compounds that were floating freely in water and 55 percent of those bound within solid particles. The levels of these declines were high enough that it was expected that bacteria, invertebrates and plants could thrive if reintroduced into the material.
Companies working in the oil sands region, which have a vested interest in improving the future of this now-notorious landscape, wanted to know if this approach could provide them with a new remediation strategy. That interest became the basis of an NSERC Collaborative Research Development grant with Weisener and Ciborowski. The grant would support laboratory testing at the university’s Great Lakes Institute for Environmental Research as well as in on-site mesocosms in northern Alberta. “We started to monitor the process to see if plants and a healthy microbial and aquatic community would establish,” says Weisener, adding that the results thus far have been impressive. “This was like a virtual banquet for this GI-treated material.”
Weisener and Ciborowski subsequently took out a patent on the technique, then engaged some graduate students to explore its implications. Master’s student Danielle VanMensel has been assessing the response of microbiological communities in GI-treated tailings, while master’s student Chantal Dings-Avery and doctoral student Thomas Reid have been examining how these materials respond to the field environment.
Environment Canada has also helped the team get to areas near Fort McMurray that have remained untouched by any kind of human development. According to Reid, these sites serve as valuable biological and chemical reference points, demonstrating the kind of wetlands the region would naturally support.
Weisener points out that oil sands operators already spend millions of dollars restoring the places where they work, often turning what had been a near-desert before extraction into grassland, forest or wetlands. While the very term “irradiation” may not sit well with many critics of this branch of the petroleum industry, the process poses none of the long-term health hazards typically associated with nuclear products. It has, in fact, been long used for extending the shelf life of fruits and vegetables and for municipal wastewater treatment.
While many people may be more comfortable with treatment technologies such as ultraviolet light exposure or ozonation, Weisner points out that these familiar and well established methods are almost exclusively suited to water. “The advantage of GI is that it not only works on water but also opaque or translucent materials,” he says. “If you’ve got muddy waters or turbid solutions, sometimes UV treatments and ozonation won’t work in that kind of environment.”
Even more significantly, GI’s ability to restore tailings and sediments at the bacterial level could represent unprecedented progress for “kick starting” reclamation efforts. The working assumption behind this treatment strategy is that radiation efficiently disrupts the cyclic structure of constituents within naphthenic acids, neutralizing their toxic effect and leaving the local environment clear for biological activity.“This method could potentially help the whole ecosystem recover more quickly because bacteria are the front line,” Weisner says. “Bacteria are both consumers and producers and are the primary producers in chemosynthesis, so they will influence the chemical environment, which allows other forms of life to establish.”