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Engineers at the University of Alberta, Canada, have developed a process that uses solar energy to treat waste water created by the oil sands extraction process.
Contaminated water from oil sands mines is contained in large “tailings ponds” with sand, clay and any residual oil to allow it to settle and solidify. Although it can take up to 30 years for the bottom layers to separate and dry out, the water in the ponds is processed to remove harmful chemicals. These include various salts, benzene, acids and hydrocarbons that are toxic to fish and waterfowl.
The tailings ponds at the Alberta oil sands mines cover an area of more than 100 square miles. Current treatment processes to treat the oilsands “tailings” use UV lamps as a light source, are seen as expensive and energy intensive.
Researchers at the University of Alberta have developed a process that uses sunlight and chlorine, that is cheaper and can be applied to the tailings immediately.
The sun's energy partially removes organic contaminants due to the direct sunlight. When the sunlight reacts with the chlorine added to the wastewater, it produces hydroxyl radicals, powerful oxidative reagents, that remove the remaining toxins more efficiently. The chlorine leaves no residuals as the sunlight causes it to decompose.
In laboratory-scale tests the solar UV/chlorine treatment process was found to remove 75 to 84 per cent of these toxins.
Gamal El-Din, a researcher on the project from the University of Alberta, said: “This solar process is treating the wastewater on the top of the tailings ponds right now. 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.
"Because we are limited by the sunlight's penetration of the water, 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 water 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.”
“This process has been gaining a lot of attention from the oil sands industry. We're now seeking funds for a pilot-pant demonstration and are looking at commercializing the technology.”