NEW ORLEANS — Feb. 24, 2016 — Wastewater treatment plants catch 90 percent or more of the tiny pieces of plastic in wastewater, but they still release a huge amount into rivers, according to a press release.

Researchers found that the amount of microplastics being released daily with treated wastewater into rivers ranges from 15,000 to 4.5 million microplastic particles per day per treatment plant.

The new findings were presented last week at the 2016 Ocean Sciences Meeting, co-sponsored by the Association for the Sciences of Limnology and Oceanography, The Oceanography Society and the American Geophysical Union.

Timothy Hoellein, an assistant professor at Loyola University Chicago, and colleagues studied urban rivers in Illinois and found that wastewater treatment plants were a source of microplastics in 80 percent of the rivers, regardless of the size of the river or the size and type of wastewater treatment plant.

What’s more, these tiny plastic particles carry potentially harmful bacteria and other pollutants on their surfaces.

The researchers found that in each river, the microplastic particles discharged from wastewater treatment plants were home to bacterial communities that were more likely to be potentially harmful than the bacteria found in the rivers.

“[Wastewater treatment plants] do a great job of doing what they are designed to do — which is treat waste for major pathogens and remove excess chemicals like carbon and nitrogen from the water that is released back into the river,” Hoellein said in the release. “But they weren’t designed to filter out these tiny particles.”

Scientists are now working to establish how much plastic stays in the rivers and how much ends up in the oceans. Studying microplastics in rivers could help scientists better understand the entire lifecycle of these tiny pieces of plastic — from land to the ocean, Hoellein explained in the release.

You can find the entire release here.