Water Sector

Consortium researches impact of ‘Bubble Barrier’ on microplastics in treated wastewater

A research consortium, comprising the water utility PWN, Hollands Noorderkwartier Water Authority (HHNK), The Great Bubble Barrier and KWR, will start a project on 1 June which should curb the flow of microplastics from treated wastewater into surface water. Concretely, a Bubble Barrier will be installed at the wastewater treatment plant in Wervershoof, in the Province of North-Holland. The consortium is thus taking a step towards understanding and reducing the presence in surface water of microplastics, which could represent a hazard for human health and the environment.

The partners will research the amount of microplastics present in the treated wastewater (effluent), the performance of the Bubble Barrier regarding microplastics with a length of 0.5-0.02mm, and the improvement and standardisation of microplastic measurement methods. The project has been prompted by the growing use of microplastics and plastics, which end up in surface water via wastewater, and the possible implications for public health. Because of the societal importance of this research, it is being co-funded by the TKI Water Technology programme of the Ministry of Economic Affairs and Climate Policy and by the PWN water utility.

Invisible wall of bubbles

This project will make use of the Bubble Barrier, which is a proven technology for the removal of plastics larger than 1mm from flowing rivers and canals. One of the research questions to be answered is whether this screen is also suitable for intercepting microplastics.

A pilot carried out in the IJssel showed that the Bubble Barrier intercepted an average of 86% of the test material. The Bubble Barrier’s tube has holes in it through which air is pumped out, creating a wall of bubbles. Thanks to a river’s natural current and the diagonal positioning of the Bubble Barrier, the plastic is guided to the river bank. There, the plastic can then be removed from the water, without interfering with the fish or vessels, thus preventing it from flowing into the sea.


A similar set-up will be used during the research at the HHNK wastewater treatment plant in Wervershoof, which will measure whether the Bubble Barrier also intercepts microplastic particles of down to 0.02mm in length. ‘There’s an urgent need to fight against the presence of microplastics in fresh surface water,’ says Philip Ehrhorn, Co-Inventor and Head of Technical Development at The Great Bubble Barrier. ‘Now that we know that the Bubble Barrier has an impact on plastics larger than 1mm, we feel that the most logical next step is to further research the possibilities and limits of the Bubble Barrier to increase our impact.’

HHNK manager, Ruud Maarschall: ‘Our wastewater treatment plants (WWTPs) remove nitrate, phosphate and suspended particles from wastewater. But we still don’t know a lot about the amount of microplastics in the treated wastewater. Nor do we yet have an adequate method to determine their precise amount. And since we work on producing clean and healthy water every day, this research is really a must for us.’

Protecting the IJsselmeer source

‘PWN produces healthy drinking water for the population of North-Holland province,’ says Joke Cuperus, the water utility’s CEO. ‘Our water source is lake IJsselmeer, which receives treated wastewater. We want to care for and protect this source, and we also want to keep the cost of drinking water as low as possible. The treatment process should not become more complicated than it is already.’

Water research institute KWR has been studying the impact of plastics in surface water for a long time. ‘Within the European TRAMP project, for instance, we are mapping out the extent to which Dutch inland waters are polluted with extremely small plastic particles,’ says KWR’s Frank Oesterholt. ‘It’s becoming increasingly clear that microplastics are also present in fresh surface water. These particles come from personal care products, cleaning products and synthetic clothing, or result from the degradation of larger plastics. We want to gain more insight and find effective solutions to stop the proliferation of these microplastics.’

The Great Bubble Barrier won the 2016 Plastic Free Rivers Makathon, an initiative of PWN and Rijkswaterstaat. The mission of The Great Bubble Barrier is to free rivers and canals of plastic, and thereby prevent the pollution of the oceans and protect the global ecosystem.

It is expected that the conclusions drawn from the project’s initial results will be made known this year.