The Freshman-project

The sweetness of brackish water

Water company Dunea supplies drinking water to 1.3 million people in the city of The Hague and surrounding municipalities (southwest Netherlands). Water supply is based on a managed aquifer recharge system, installed in the coastal dunes in the 1950s. Pretreated river water is infiltrated in the coastal dunes and pumped up again after a residence time of six weeks. The system is effective in maintaining a fresh groundwater body in the coastal dunes, however further expansion of this ‘strategic freshwater reserve’ is restricted by the presence of brackish groundwater underneath the freshwater body (Figure 1). We started a pilot project in February 2022 to investigate the potential of brackish groundwater as additional source of drinking water. Brackish groundwater is an excellent feedwater for medium-pressure reverse osmosis membranes and can be desalinated at acceptable energy input and costs. Extraction of brackish groundwater in the coastal dunes may also have strategic benefits, as it could result in a downward shift of the interface between fresh and brackish groundwater, enabling a gradual growth of the strategic freshwater body in the coastal dunes. This will increase the robustness of Dunea against potential interruption of river water supply to the dunes due to e.g. pollution incidents.

Brackish groundwater may thus provide an additional source of drinking water and its extraction may result in an increase in Dunea’s strategic fresh groundwater reserve1, 2. These combined benefits of brackish groundwater extraction are referred to as the Freshman concept (Figure 1) and have been tested in a field pilot in the coastal dunes of The Hague, lasting from February 2022 till July 2023 (1.5 years).

Methods

In 2021, a field pilot was set up at Dunea’s primary drinking water production site in the coastal dunes of The Hague (Figure 2).

The pilot consists of the following infrastructure (Figure 3):

Conclusions

About LIFE

The LIFE programme co-finances projects in the areas of resilience to water scarcity, droughts, forest fires or floods, adaptive technologies for economic sectors, and safeguarding natural resources. It provides action grants for best practice, pilot and demonstration projects that contribute to increased resilience to climate change. The climate sub-programme also promotes the development and implementation of EU policy on climate change adaptation, best practices and solutions for climate change adaptation, including ecosystem-based approaches and knowledge sharing.
In the programme this project is known as: LIFE19-CCA_NL_001222 LIFE_FRESHMAN.

Questions/contact

Nederlandse informatie over dit  project

Do you have questions about this project? Go to the questions and answers page to find an immediate answer. Do you have other questions or are you a journalist? Please send an email to communicatie@dunea.nl.