Ultraviolet light is an economical and simple way to clean up the residue, or “tailings,” left over from extracting oil from Canadian tar sands. But now scientists at the University of Alberta have found an even cheaper way: Ditch the UV lamps and replace them with sunlight.
Ponds containing oil sands tailings have various contaminants, including suspended solids, salts and other soluble material such as acids, benzene and hydrocarbons. Using conventional decontamination methods on “oil sands process affected water” (OSPW), as it’s known, takes at least 20 years to get it clean.
Using UV lamps and chlorine makes the process virtually instantaneous. And now professors Mohamed Gamal El-Din and James Bolton have found that using sunlight instead of UV lamps does the job just as efficiently but at a much lower cost.
In an article published in the journal Environmental Science & Technology, the researchers explained that direct sunlight removes organic contaminants, and adding chlorine, or simple bleach, to the mix removes the toxins more efficiently. The chlorine itself isn’t left behind because the sunlight causes it to decompose.
This method works well in the laboratory, where tests found that solar UV and chlorine removed between 75 percent and 84 percent of the toxins in the tailings. Decontamination in the field, though, is a bit more difficult. Tailings are contained in and on the surface of ponds of water.
“With this solar process, right now, the wastewater on the top of the tailings ponds is being treated, Gamal El-Din told University of Alberta News. “But because we have nothing in place at the moment to circulate the water, the process isn’t being applied to the rest of the pond.”
That doesn’t daunt the research team. “We know it works, so now the challenge is to transfer it into the field,” Gamal El-Din said. “This alternative process not only addresses the need for managing these tailings ponds, but it may further be applied to treat municipal wastewater as well.”
Besides, because the process is solar-driven, its cost would be minimal compared to all known alternatives.
According to Gamal El-Dinthe project has already attracted industry attention and the team is working to raise money to make the technology commercially viable.
“Because we are limited by the sunlight’s penetration of the water,” Gamal El-Din said, “we now must come up with an innovative design for a mixing system like rafts floating on the ponds that would circulate the water. Installing this would still be much more cost effective for companies.
“It is expected that the UV/chlorine process will treat the OSPW to the point that the effluent can be fed to a municipal wastewater treatment plant, which will then complete the purification process sufficiently so the water can be discharged safely into rivers,” he said.
By Andy Tully of Oilprice.com
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