Rivers of plastic bits
MILLIONS of tiny pieces of plastic are escaping wastewater treatment plant filters and winding up in rivers where they could potentially contaminate drinking water supplies and enter the food system.
Microplastics – small pieces of plastic less than 5mm wide – are an emerging environmental concern in seas, where they can harm marine animals. Although the majority of ocean debris – including plastics – is transported to oceans from rivers, much less is known about how microplastics are entering rivers and affecting river ecosystems, according to Timothy Hoellein, an assistant professor at Loyola University Chicago.
Fish and invertebrates eat the tiny pieces of plastic in rivers, which then make their way up the food chain – possibly ending up on our dinner plates, he said. Like microplastics in the ocean, plastics found in rivers carry potentially harmful bacteria and other pollutants on their surfaces.
Hoellein previously found that water downstream from a wastewater treatment plant had a higher concentration of microplastics than water upstream. His new research on 10 urban rivers in Illinois supports this initial finding. Although initial estimates suggest that wastewater treatment plants are catching 90% or more of the microplastics, the amount being released daily with treated wastewater into rivers is significant, ranging from 15,000 to 4.5 million microplastic particles per day per treatment plant.
Wastewater treatment plants were a source of microplastics in 80% of the rivers studied. The research also found the tiny plastic particles to host bacterial communities.
“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. “But they weren’t designed to filter out these tiny particles.”
The research also found that microplastics not only stay in ecosystems for a long time, but travel a long way from their point of origin – some as far as 2km downstream.
This supports the idea that rivers can transport plastic and pathogens over long distances and eventually, introduced into various ecosystems, Hoellein said. Scientists are also studying how much plastic stays in rivers and how much ends up in oceans to better understand the lifecyle of these tiny pieces of plastics. – American Geophysical Union