Unique cooperation between Belgium and the Netherlands creates new natural filter to purify historically polluted groundwater in Grenspark Kalmthoutse Heide
In the Grenspark Kalmthoutse Heide, on the border between Flanders and the Netherlands, an innovative phosphate filter was officially delivered today. Thanks to close cooperation between the two countries, historically polluted groundwater will now be purified in a natural and energy-free way, before it drains into the vulnerable Dutch nature reserve the Groote Meer. The project shows how cross-border cooperation can contribute to sustainable nature and water management in a shared landscape.
Historic soil pollution tackled
The Steertse Heide, a subarea of the Grenspark Kalmthoutse Heide, is a former agricultural area that today functions as one large water collection basin. Rainwater collects there and drains via ditches towards the Groote Meer in the Netherlands. Due to intensive agricultural use in the past, the area became heavily laden with fertilisers, hindering the development of valuable heath and fen vegetation.
"Long-term agricultural use has led to high loads of fertilisers such as phosphates and nitrates. As a result, fast-growing species start to dominate in De Groote Meer. You see that evolving from reed formation to the rise of birch and pine trees, and so step by step a large part of the biodiversity is disappearing." - Jan Weverbergh
Although nitrates disappear from the soil relatively quickly, phosphates are particularly persistent and remain present in the water system for a long time. To tackle that load, a first phosphate filter was already installed on Dutch soil in 2020. That installation purifies water from the northern part of the Steert Heath. The success of that first filter gave the confidence to expand the project.
Natural water purification through unique collaboration
The operation of the system is technically simple but effective. Rainwater is collected and flows through a filter layer of iron sand, a residual product from drinking water extraction. Phosphates bind to that sand, without pumping or energy consumption. Thus, the water is sustainably purified before crossing the border.
The new, second phosphate filter focuses on the southern part of the area. It is located on Belgian territory but is financed by the province of North Brabant, an investment of no less than €1.4 million. This investment is the result of years of cross-border cooperation within the Grenspark Kalmthoutse Heide. Flemish and North Brabant governments, site managers and water partners have been working together for years to create one coherent landscape, without being hindered by administrative borders.
"The Grenspark is an example of how cooperation across borders can lead to better nature quality and sustainable water management," said Lukas Jacobs, chairman of the Grenspark. "This project shows that shared responsibility also leads to shared benefits, for people and nature."
"The Groote Meer is a vulnerable nature reserve threatened by phosphates and dehydration. With these measures, we provide the area with clean water that benefits biodiversity in the Groote Meer and further in the Brabantse Wal nature reserve. Water management has also been improved, making the new ecosystem much more resilient. I am proud of the years of close cooperation with the Flemish and North Brabant partners. Everyone has taken responsibility for this robust nature area. After all, nature and water do not stop at national borders."- Hagar Roijackers, member of the Provincial Executive for Nature, Environment and Rural Development
More than water treatment
The completion of the phosphate filter is part of a broader nature restoration operation. At the same time, the Evertandven, a four-hectare filled-in fen, was rearranged. Natural fluctuations in the water level will recreate a dynamic ecosystem with a greater variety of plant and animal species.
Cooperation
The completion is the result of a collaboration between the following parties.
· Grenspark KalmthoutseHeide coordinated the project as project manager.
· Province of Noord-Brabant provided the funding
· Water board Brabantse Delta was involved for expertise, as responsible for water quality and for monitoring after completion.
· The Flemish Government's Agency for Nature and Forests provided expertise and also made available the plot on which the filter is built.
· Witteveen + Bos provided study and design work and site supervision.
· As a specialist in hydraulic engineering, Heyrman-De Roeck took care of implementation on site.
· Some volunteers provided site knowledge and expertise from a background as engineers.
