Princeton grads fight microplastic pollution with new filtration system

💧 Microplastics are found in 93% of our bottled water

💧 Two Princeton grads developed a system to filter out harmful microplastics

💧 The system is being tested in Atlantic City

ATLANTIC CITY — Two former Princeton University graduate students are testing a filtration system in Atlantic City that would, for the first time, filter microplastics out of the water.

Why microplastics?

Microplastics are found in all of our oceans and in more than 93% of our bottled water, said Yidian Liu, co-founder and co-creator of The Polygone System.

So, they are hard to avoid. The problem is that microplastics are very small, “microscopic” if you will, less than 5 millimeters in diameter. They enter the body at about one millimeter, almost invisible to the naked eye, Liu explained. They are small they can penetrate our cells and stay in our bodies for a long time.

Microplastics are bacteria that carry other harmful bacteria.

“We found out this year that microplastic quantity and sizes that are found in human bodies have really increased in comparison to many years ago. That data is very alarming because we don’t know what is the threshold for microplastics to actually cause fatal health threats to our next generation,” Liu said.

Microplastics can cause metabolism and reproduction dysfunctions, so they are very harmful, she added.

“We don’t want to wait for this to become a confirmed threat so that is why we picked microplastics as our mission,” Liu said. The “we” she is referring to is her co-founder and co-creator, Nathaniel Banks.

The Polygone System

Liu and Banks created the Polygone System when they were graduate students at Princeton University in 2021. They were first going to look into waste infrastructure to collect larger plastic waste from the waterways.

But, they found there was a system already out there that sorts and collects plastics. What was missing was a system focused on microplastics, so that became their aim.
The goal of Polygone is to educate the public about the harm of microplastics, and remove microplastics from the water, Liu said.

How does Polygone work?

The filter looks like a fibrous brush, which is a biomimetic form of aquatic plant roots. Aquatic plant roots have many fibers, and they often attract smaller particles in the water, including microplastics.

“Our system is called an artificial root filter. It’s designed to collect the top layer of microplastics without interfering with aquatic wildlife,” Liu said.

Since most plastic is either neutrally buoyant or lighter than water, they are usually concentrated either on the surface level or in the first 30 centimeters of the water column, she said.

The Polygone System will be deployed towards the top level of the water column, and collect microplastics while the fish and other wildlife can still swim around it.

Why Atlantic City?

Liu and Banks were trying to find partners. The Atlantic City Utilities Authority (ACUA) was interested.

Liu said it was the perfect part because ACUA already has a water treatment plant on the site plus a commercial windmill farm. So, they were very open to forming a partnership with Liu and Banks to move forward with the system.

Polygone System is funded by several grants. The biggest one is The NOAA Sea Grant Marine Debris Challenge, which supplies systems in a coastal state for removing larger marine debris or microplastics, Liu said. Another big grant comes from the NJ Commission on Science, Innovation, and Technology.

Future of Polygone

Currently, Polygone is deployed in the ACUA water treatment plant site for a 12-month pilot program, where water samples are taken continuously. Afterward, the hope is to keep the system in place there permanently.

About 720 filters have been installed, which covers the entire width of the channel. That means the water will pass through the filter, and microplastics will be filtered out, Liu said.

So far, Liu has collected 900,000 microplastics every week, so the system is working.
The goal is to have a network of barriers to stop microplastics from entering broader water channels.

“We want to be strategic where we place our systems. Wastewater treatment plants are big contributors to microplastic emissions. We want to set up our systems in as many possible,” Liu said.

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