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Grasping at straws

It’s all in the eye of the beholder.

Where some see waste moving out the back end of combines, Catherine Hui Niu sees great opportunity.

“Can we explore new use of those materials? Can we make better use, discover new technology to reuse those materials, recycle them, or add value to them?” asked Niu, associate professor in the Department of Chemical and Biological Engineering at the University of Saskatchewan.

In particular, barley straw has caught the eye of Niu and her team of researchers.

When pre-treated, it is showing potential as an environmentally friendly material that could be used to help soak up certain types of antibiotics and other industrial organics polluting waterways.

She said pharmaceuticals cannot be completely metabolized by animals or humans, and these have become an increasingly common pollutant in water systems.

In particular, large amounts of antibiotics go into water and currently there are no effective methods to remove them.

“Nowadays, the methods to treat antibiotics are very limited. The majority of antibiotics are not removed from water after treatment from a regular wastewater treatment plant. There’s no strict policy regulation for that, but it doesn’t mean it’s healthy for humans and animals,” she said.

Excreted traces of pharmaceuticals end up in sewage and from there into the environment, which has raised concerns about potential risks to human health and ecosystems.

“It can contaminate the water and also the soil because farmers may reuse the water. It goes back to the land,” she said.

“If there’s antibiotics those bacteria can pick them up and they develop resistance. Also, if you water the crops it may later affect the food.”

Barley straw attracts pharmaceutical pollutants by adsorption.

However, adsorption capacity needs to be enhanced to make them useful for large-scale clean-up efforts.

To do that, the barley straw is treated with phosphoric acid and heat so it can more effectively take on compounds from contaminated water.

“We found that treated barley straw, the adsorption capacity for antibiotics is much higher than raw barley straw. It’s also quite stable and absorbs water quickly,” she said.

Researchers are also experimenting with canola meal, oat hulls, flax shives and wheat straw.

“If we put these raw materials into water directly there’s some component release. The water becomes slightly yellow, so that means organics are being released. But after our treatment you won’t see those releases. It’s quite stable,” she said.

Using the Canadian Light Source at the University of Saskatchewan, the research team discovered the mechanisms of how the pre-treated barley straw works as a medium.

Adsorption qualities improved after subjecting the straw to chemical and microwave heating.

Researchers studied samples of pre-treated barley straw exposed to norfloxacin, a type of quinolone antibiotic frequently used to treat bladder infections, which has been detected as a pollutant in some water and sewage samples.

She said the capacity is about six times higher than untreated raw barley straw and considerably higher than many other materials.

Niu foresees a finished product that will resemble a flow through column filter where antibiotics are removed from the contaminated water.

Once the filter is saturated, a small amount of acid solution put inside could partially desorb or elute the antibiotics and regenerate the column.

Niu is optimistic that a wide-scale filter system can be developed, but she cautions that the researchers are at least three years away from commercialization testing.

However, she can see the day when crop debris will be used more extensively.

“If those technologies are really successful, finally the farmers can sell those products. We can manufacture them. It’s another revenue stream.”

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