Five years ago, Claire Els van Delft began suspicious of plastic waste on Katwick Beach in Holland It did not come from visitors or the sea, but from the mouth of a nearby river.
“We started collecting trash and noticed, near the entrance to the river, bits of fresh water coming in — all kinds of plastic,” she says. “Tampun cases, brush bristles, but also fragile packages, drink packages, everything.”
Sure enough, when the volunteers sifted in an oil barrel filled with the waters of the Oude Rijn, they saw small plastic particles in the duckweed. “We saw so much pollution, we were shocked,” says Van Delft, co-founder of a local charity. Coast Busters.
Fast forward to July 2022, and Katwijk is the site of the world’s first river”bubble barrierAn experimental concept where a 120m stream of rising bubbles, along with a stream of water, pushes plastic waste to one side to be collected.
“We put a perforated tube at the bottom of the waterway, at an angle, and then pump it through compressed air: The rising air bubbles create an upward current that lifts the plastic from the water column to the surface, and then at the surface—along with the river flow—everything is pushed to one side,” he explains. Philip Ehrhorn, chief technology officer of Dutch startup The Great Bubble Barrier. “Here, we get the flow from the pumping station, or the wind can also push the garbage into the water collection system.”
The company, which is run by a team of sailors, surfers and water enthusiasts, has won an international award Green Challenge Zip Lottery In 2018, its first permanent courses began pilot in channel in Amsterdam the following year. So promising is this experience that it convinced the Rijnland Water Board and the 12 municipalities and regions of Holland Rijnland and Zuid-Holland – along with Coast Busters and local fundraisers – to invest €470,000 to build river bubble roadblock.
Jacko Naip, deputy mayor of Katwick, said he saw the local plastic problem with his own eyes when he was called to clean up trash on the beach. “Plastic pollution is a growing problem worldwide, affecting societies as well as the environment, [and] Unfortunately, your case is no exception. “We notice plastic contamination by beach visitors, leaving behind wrappers and other plastics, but we are also the last stop before all the plastics are collected along the Oude Rijn flowing into the sea. With this bubble barrier, we can stop those plastics.”
Bas Knapp, executive board member of the Rijnland Water Board, believes the bubble barrier will not prevent fish migration, and is investing €42,000 per year to operate it. “We did a test that showed that in the pumping station, only 1 out of every 233 pieces of plastic larger than 1 mm is removed from the water. [by its filter]But with the bubble barrier in place, we expect to remove between 86% and 90% of the plastic pollution. The trial was incredibly promising. This is one of our biggest estuaries, and it’s a really good place to put a promising pilot to work to try and reduce Plastic seeps into the sea.”
Anne-Maric Evelyn, co-founder of The Great Bubble Barrier, is working on scaling up this technology, discussing a potential barrier in an estuary in Portugal and another project in Southeast Asia. “One of the requests that we sometimes get is a big international port like Rotterdam – there, it’s 20 meters deep but that’s [currently] Out of range,” she admits. “It’s also hard if there are a lot of ships, and they’re dredging a few times a year.”
But many believe this technology is still promising for specific scenarios. Dr. Frans Buschmann, a researcher in environmental hydrodynamics from the independent Deltares Institute, tested the barrier in Amsterdam, using about 1,000 tagged tangerines. “We released them at several points and counted the number of those captured,” he says. “On one side of the watershed system it was up to 90%; sometimes on the other side, we noticed it was much lower, probably because there was one spot where the bubble density was not very high, and some tangerines were going through there.”
He adds that items that were fully floating can be blown over the bubble barrier by wind, making them less effective, but he believes it’s still a “promising technology.” [with] Great potential.”
However, some researchers point out that Plastic in rivers doesn’t necessarily end up in the oceanin spite of It can still damage ecosystems and human livelihoods. River systems differ, too, says Tim van Emerek, associate professor in the Hydrology and Water Quantity Management Group at Wagengen University. “When thinking about rivers globally, just imagine how diverse they are, from the narrow canals of Amsterdam and Leiden, to deltas as large as the Mekong,” he points out. “Most tech solutions, like the Bubble Barrier, only cover a range of them, emphasizing that there will always be a need for a set of solutions. Of course, consuming and polluting less plastic will help no matter where you go, and it may actually have biggest impact.”
Back in Katwijk, there are plans to build a visitor and education center next to the bubble barrier to do just that, and hopes are high. Under the summer sun, a stream of gentle bubbles flows on the surface of the river, like a jacuzzi. “We were looking forward to opening with a swimsuit!” Van Delft says, quite seriously.