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Scientists removing phosphate contamination in water with sponge filtering

Water Pollution Solution
Posted at 10:51 AM, Jun 14, 2021

EVANSTON, Ill. — Phosphorus is an essential nutrient. Every living organism on the planet requires it and there is no synthetic substitute. Half the world’s food supply is fertilized by its chemical derivative – phosphate. And we’re running out. Add to that, phosphate runoff in streams and lakes is causing toxic algae blooms killing aquatic life, and you find the catch-22.

Scientists say maintaining a delicate balance is important. Phosphorous normally occurs naturally in small quantities. But its increased use in fertilizer for agricultural purposes negatively impacts water quality and ecosystems.

“It can stimulate the growth of algae, too much is not good, and too little is not good,” said Craig Stow, a research scientist at the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory.

Increased temperatures, light penetration, and phosphate run-off pollution have caused harmful algae blooms in rivers, streams, and lakes for years.

“Very wet conditions cause a lot of runoff from agricultural yields, and that goes into the major rivers and tributaries,” said Stow. “So, some of wetter years tend to be worse years for algal blooms.”

Satellite imagery over Lake Erie shows some of the dangerous algae blooms that have killed aquatic life and contaminated drinking water.

But now, a team of scientists has developed a way to target and remove phosphate from polluted waters.

“Phosphate, in particular, is a very menacing problem,” said Vinayak Dravid, director of the Northwestern University Atomic and Nanoscale Characterization (NUANCE) Center.

He and his team have developed a membrane that they say can soak up 99% of the phosphate ions from water.

“Just like a household sponge absorbs water and soap and you can wash the dishes, this particular sponge membrane absorbs only phosphate,” said Dravid.

“This is going to be a lot like a conventional sponge, but it has a special coating on it,” explained Stephanie Ribet a Ph.D. student and study co-author. “We will load our column full of the membranes and then we will run our contaminated water with a pump through the column and then we'll get the water out.”

Last year, the team successfully used the same kind of nanotechnology to soak up oil from water.

“We have been expanding for a lot of pollutants right now, such as heavy metals, microplastics, as well as in soil and air also,” said Vikas Nandwana, a research assistant professor of material sciences at Northwestern.

In addition, the sequestered phosphate can be reused.

“You take that absorbed phosphate to another tank and slightly change the condition to basic and all the phosphate gets released,” said Dravid. “And that allows it to be used many times potentially.”

The research, which was published in "The Proceedings of the National Academy of Sciences" could provide the kind of new filtration technology that they say is sustainable and inexpensive.

“I think there's an opportunity to show that not only is it the right thing to do, but it is scalable, and it has a business proposition,” said Dravid.

It’s a possible lab innovation that could help preserve life as we know it.