Canadian researchers have developed a process to remove contaminants from oil sands wastewater using only sunlight and nanoparticles.

According to the University of Waterloo, the new method is more effective and less expensive than conventional treatment methods such as chlorine or membrane filtering.

Tests carried out by the research team showed that photocatalysis — a chemical reaction that involves the absorption of light by nanoparticles — can completely eliminate naphthenic acids in oil sands wastewater within hours.

Publishing their findings in the journal Chemosphere, the researchers said that one day of solar photocatalytic treatment eradicated naphthenic acids and other acid extractable organics from raw oil sands wastewater.

Nanoparticles become extremely reactive when exposed to sunlight and break down the persistent pollutants in their individual atoms, completely removing them from the water. This treatment uses only sunlight for energy, and the nanoparticles can be recovered and reused indefinitely.

Naphthenic acids pose a threat to human health and the environment and are the most significant environmental contaminants that result from petroleum extraction from oil sands deposits. They remain in tailing pond wastewater for decades.

“With about a billion tons of water stored in ponds in Alberta, removing naphthenic acids is one of the largest environmental challenges in Canada,” said lead author Tim Leshuk, a PhD candidate in chemical engineering at Waterloo. “Conventional treatments people have tried either haven’t worked or if they have worked, they’ve been far too impractical or expensive to solve the size of the problem. Waterloo’s technology is the first step of what looks like a very practical and green treatment method.”