Dunea working on future-resilient freshwater supplies – FRESHMAN

FRESHMAN

The innovative FRESHMAN project is studying the extent to which the dunes can contribute to a more sustainable and robust drinking water supply. That involves a three-year pilot project near Scheveningen. FRESHMAN, which stands for ‘sustainable FRESHwater MANagement in coastal zones’, was set up by Dunea in collaboration with KWR, Allied Waters, and two Belgian water companies (De Watergroep and IWVA).

Safeguarding drinking water supplies

At present, for the purposes of drinking water production, Dunea uses a freshwater lens that goes down to a depth of more than 90 metres in the dunes. Pre-treated river water is pumped from the Meuse and Lek to the dunes and infiltrated into the subsurface through infiltration ponds to replenish the freshwater lens. After passing through the soil, this water is pumped up again for use as drinking water. As river discharges become increasingly erratic and the risk of pollution increases, this source of water is becoming vulnerable. That is why Dunea is looking for additional sources and more treatment techniques in order to safeguard supplies of drinking water under all circumstances. The drinking water supply needs to be able to cope with factors such as population growth and climate change.

Pilot project with dual effect

The groundwater immediately below the freshwater lens used by Dunea is brackish and therefore unsuitable for conventional drinking water production. During the FRESHMAN project, this brackish groundwater will be taken from an extraction well for three years. It will then be desalinated using reverse osmosis (RO). That leads to two results.

Firstly, after desalination, brackish groundwater can be used as an additional source for the production of drinking water: the fresh permeate flow is added to the dune water that is pumped up as usual before going through the standard treatment process. The saline concentrate stream is discharged into the sewer.

The second effect of this extraction process is that pumping out the brackish groundwater creates more space in the subsurface for the freshwater lens and increases the strategic freshwater supply. The growth of the freshwater lens is closely monitored in different monitoring wells. KWR is closely involved in these geohydrological monitoring and analysis activities.

Pieter Dammers (Dunea; left) and Teun van Dooren (KWR; right) at the borehole of the first monitoring well, which has already been installed in the dunes at Scheveningen pumping station

One monitoring well has already been installed in the dunes near Scheveningen to determine the baseline situation. Applications will be submitted this year for all the permits required for the pilot project and the well field will take shape. After a test phase, the pilot project will begin in the second quarter of 2021 and continue until mid-2024.

LIFE FRESHMAN: Sustainable freshwater management in coastal zones

Concrete solutions for water and climate

FRESHMAN was made possible by LIFE, a European Union subsidy programme. LIFE supports innovative projects in line with European policy for nature, environment and climate. The FRESHMAN project was awarded in April 2019. It has a 360° focus on concrete solutions and practical applications in the field of water and climate. More than €3 million has now been released for innovative research into the extraction and treatment of brackish groundwater. In addition to the pilot in Scheveningen, the project will be replicated by the Flemish research partners in Avekapelle (Belgium) to investigate the potential of brackish water extraction in different conditions.

The first monitoring well in the dunes near Scheveningen pumping station, with monitoring well filters, mini-filters, a salt monitoring cable and a fibre-optic cable

Drinking water from brackish groundwater

Brackish groundwater for the production of drinking water is already being extracted in various locations worldwide and so this approach is not new. KWR has conducted a similar study with Vitens in Noardburgum and with Brabant Water in Zevenbergen. In FRESHMAN, we are moving ahead on the basis of exploratory research conducted by Dunea, KWR, Arcadis and Deltares as part of the COASTAR knowledge programme.

Brackish water extraction in the dunes as part of the COASTAR knowledge programme

COASTAR is also investigating the feasibility of brackish water extraction on a regional scale with geohydrological model calculations for the Meijendel and Berkheide extraction areas.

Long-term security

For Dunea, the research under the auspices of COASTAR and FRESHMAN represents an opportunity to make supplies of drinking water more secure in the long term. Depending on the results of FRESHMAN, it should become clear whether the extraction of brackish groundwater will be included in the robust source mix that the water company wishes to establish for the long term.