A MORE SUSTAINABLE WATER CYCLE

If it is developed in the Netherlands, it sells itself

Roelof Kruize - Director of Waternet

In the area surrounding Amsterdam there are hundreds of hectares of polder land, some six metres below the water level. Every year, some 10 million cubic metres of what is called seepage water rise to the surface here. This seepage water is less salty than seawater, but still disastrous for agriculture. It is a headache for farmers in the area and for Waternet. Kruize: “We flush the ditches with water from the IJsselmeer. Ten times the amount of water is needed to clean them. This means more than 100 million cubic metres of IJsselmeer water per year.

A changing climate is a cause for concern

The problem is growing: as the summers become drier, the polders are sinking further due to subsidence. Ever more IJsselmeer water is needed to keep the polders usable for agriculture, warns Kruize. “We would benefit from using IJsselmeer water with care.

For this reason, Waternet set out in search of a structural solution that takes account of the changing climate and is both sustainable and affordable. “We are going to pass seepage water – water that is currently disposed of as if it were waste water – through a membrane to turn it into drinking water.”

Filtering seepage water in this way produces drinking water. And ditches no longer have to be flushed with water from the IJsselmeer.

The application affects all areas where Waternet is active: purifying wastewater, making drinking water, cleaning the surface water as well as ensuring that the surface water is neither too high nor too low. A pilot scheme is already in progress and this year the technique will be applied for the first time outside in one of the deeper polders. Kruize: “And not at laboratory scale.

Cross-pollination between disciplines

In the United Arab Emirates, among other places, salt water is already being purified by means of membranes, but the application to brackish water is new. The fact that several disciplines are combined within Waternet fosters knowledge sharing and, consequently, innovation, according to Kruize. “The most interesting innovations are at the interfaces.

Because Waternet deals with both surface management and drinking water, questions are easier to answer: “How much salty seepage is there? What is the effect of this on the surface water? How are we going to meet the standards for drinking water provision with this technique?

In the Netherlands, drinking water is currently still softened with environmentally harmful caustic soda in order to comply with NEN standards. Waternet has found a solution that is better for the environment and also complies with NEN standards. With the membrane technique, the use of caustic soda is no longer necessary. What is more, total costs are lower. Kruize: “It is more sustainable and we amply recoup the costs.

The Netherlands is a land of water

Kruize sees possibilities for the international application of the approach, for example in Bangladesh or Egypt. “The large metropolises lie in the delta and the population is moving to the cities.

Partly due to the high standards that the Netherlands sets for water quality, he expects that it can also play a guiding role here. “Around the world, the Dutch are looked to where water is concerned. It comes as no surprise that water is one of our top sectors. If it is developed in the Netherlands, it will sell itself.

View here the projects and standardization initiatives related to water.

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