Project: Seepage water | Status: completed

Client: Province of Fryslân

Project number: 000161

Description: In recent years, a great deal of work has been done on the infrastructure around the city of Leeuwarden to improve the flow of traffic and accessibility. The construction of the new ‘de Haak om Leeuwarden’ and ‘Noordwesttangent’ roads has caused groundwater problems in several civil engineering works.

Saline seepage water leaks to the surface constantly. Due to the high concentrations of macro-ions, this seepage water cannot be discharged into nearby surface water without negatively impacting nature and agriculture.

The Province of Friesland asked the CEW to research a sustainable ecological solution in combination with a technical application for the treatment of the saline water.

The CEW divided the research into an ecological solution into two parts:

– Saline nature
– Saline agriculture

The research showed that only one scenario offers
a sustainable solution for the “salty” seepage
problem that has arisen in the case of several
civil engineering works around Leeuwarden. If
the competent authority decides to carry out the
establishment of the Tearnzer Greide, it is important
to carry out additional and further investigation.
Important topics for this follow-up study are mainly
to collect more detailed and year-round data
concerning the current water system and
water quality.

For the province it is preferable to have pure salt and clean water after treatment. This water can be used again in the future in various ways, and the salt as road salt in the winter.

Seepage water can be cleaned with different types of wastewater systems. Think of membrane processes such as nanofiltration/reverse osmosis and electrodialysis, or distillation processes such as Multi Stage Flash Distillation (MSD) or Multiple Effect Distillation (MED).

The choice of system will depend on the needs of the city of Leeuwarden, other authorities and the requirements of the system. Costs and ecological aspects are important factors here; how much money does the city want to spend and which system can be used in which environment?

“Because of climate change and the related sea level rise in the future, there may be more issues with salt seepage in the coastal regions. The objective is to transform the salt issue from an obstacle into an opportunity through the application of innovative solutions.

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