Bubble Barrier
Vila do Conde

The Bubble Barrier Vila do Conde has been implemented as a pilot for the EU project MAELSTROM. If the pilot is successful the project will be adopted by the city of Vila do Conde.

The pilot part of the project is funded for 70% by the EU. The remaining 30% and the additional costs to make the project permanent are supported by the municipality of Vila do Conde, and our partners outside of the MAELSTROM consortium: Schmidt Marine Technology Partners, Stop!MicroWaste and the Engie Foundation.

The Location

Ave River,
Vila do Conde

The problem of riverine plastic pollution is universal: plastic debris is transported by rivers, crossing national and political borders, before reaching oceans.

The Municipality of Vila do Conde has taken a proactive approach to plastic pollution by partnering with the MAELSTROM team to co-design and implement a Bubble Barrier in the Ave River.

The Ave River has its source in the Cabreira Mountain (Serra da Cabreira) in the Minho Region. In its course it passes through the cities of Guimarães, Vizela, Santo Tirso, Trofa and Vila do Conde, before it flows into the Atlantic Ocean.

The Ave River was chosen because the river needed a solution to plastic pollution without interfering with daily river activities.

Bubble Barrier Vila do Conde is the first Bubble Barrier in Portugal, and the first Bubble Barrier to stop plastic pollution from flowing into the Atlantic Ocean.

The Project


MAELSTROM – Smart technology for MArinE Litter SusTainable RemOval and Management – is an EU-H2020 project bringing together 14 partners including research centres, recycling companies, NGOs, marine scientists, and robotic experts from 8 European countries.

The project is coordinated by the Italian National Research Council (CNR) and aims to implement innovative multi-level solutions for the sustainable removal and recycling of marine litter in coastal environments.


The waterway

A Bubble Barrier in an estuary

The Ave river is an estuary with high stratification (having a saltwater and freshwater mix throughout the water column). This results in estuarine circulation, meaning the incoming tide brings a flush of salt water into the river mouth twice a day, thereby reducing or even reversing the flow direction, and increasing the water level by roughly 2.5 metres. Furthermore, there will be a difference in water density between the saltwater and freshwater, which impacts the flow patterns across the water column.

The Bubble Barrier is placed in the estuarine zone of the river, and the design is adapted to all of the above-mentioned factors. Together with Deltares we have researched the impact of the changing flow velocity- and direction at our system in Amsterdam, of which the results have been translated to the design in Vila do Conde.

The Bubble Barrier Vila do Conde is the first Bubble Barrier project in an estuary. The results of the pilot will be evaluated after 1 year of operation. With this project, we aim to realise a standard design for more estuary rivers in the future.


1. Plastic in water

Plastic in the Ave River reaches the Bubble Barrier and is guided by the bubbles into the Catchment System.

2. Bubble Barrier

The Bubble Barrier is placed diagonally in the river, in a precisely calculated angle for the highest possible capture of plastics.

3. Boat traffic

Boats can pass through the Bubble Barrier without hinder.

4. Catchment System

The floating Catchment System retains the plastic catch until removal and works along with the fluctuating tides.

5. Solar panels

Solar panels – floating and roof top panels – placed in partnership with University of Malta provide part of the energy used to power the system.

6. Compressor

An electric compressor supplies compressed air for the Bubble Barrier and is placed in a container made from recycled plastic. 

MAELSTROM Consortium Partners

Bubble Barrier Vila do Conde is part of project MAELSTROM, which is co-funded by the EU and consists of the partners:

Supporting Partners

The partners outside of the MAELSTROM consortium that have supported Bubble Barrier Vila do Conde are:

Press and Media

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