Rewarding: closing water and nitrate cycles in greenhouse horticulture

The greenhouse horticulture sector in the Netherlands is working on circular food production. On the road to achieving this goal, the sector must focus on, among other things, supplying enough irrigation water in sustainable ways and reducing nutrient emissions to groundwater and surface water. Several greenhouse horticulture businesses in the Netherlands still rely heavily on the desalination of groundwater for irrigation, with concentrated salt streams as a by-product. In addition, concentrated streams are formed after irrigation. The discharge of these streams and the (sometimes unintended) discharge of irrigation water constitute the main emission routes from greenhouse horticulture to the environment.

Project idea

In this project, our aim is to provide technological solutions that will help the greenhouse horticulture sector to use water more efficiently, reducing dependence on groundwater. A second goal is to help reduce nutrient emissions. This dual objective means that we will be applying an integrated approach to the treatment of discharge water, including concentrate treatment, water recovery, and nitrogen removal and recovery (mainly nitrates).


We want to develop and evaluate integrated systems consisting of selected water treatment technologies for discharge water from greenhouse horticulture. This water is released from both the production of irrigation water and the discharge of wastewater. Most available technologies have already been tested with water streams with low to moderate salinity. In this project we will be adapting and improving these technologies, and also applying new technologies that are not (yet) used in greenhouse horticulture. We will be focusing on water streams with increasing salinity, even up to the level where those streams are saturated with salts. Our goal is not only to achieve high levels of water recovery and minimal liquid runoff, but also to selectively recover or remove nutrients.


The intended outcome of this project is a broad assessment of the technical possibilities and economic feasibility of the integrated system proposed here, including the individual treatment technologies. It is expected that all stakeholders, including policymakers, will be able to draw on this assessment to identify opportunities for the practical application and further development of this system.