Monitoring nutrient measures

In many areas of the Netherlands the surface-water quality still does not meet the WFD targets. In the present project two catchment areas in the provinces of North Brabant and Flevoland are being intensively monitored for nutrients, and innovative measures aimed at reducing the outflow of nutrients into surface water are being tested in practice. This is providing new insights into the sources and routes of the nitrogen load of the surface water, and into the effectiveness of measures taken in Dutch agricultural practice.

Wood chip bioreactor

In September 2023, a wood chip bioreactor was installed in the Vinkenloop catchment area (east Brabant) (see Image 1 and 2). The purpose of a wood chip bioreactor is to remove nitrate from the drainage water before it reaches the surface water. A portion of the drainage water is directed through the bioreactor and the nitrate it contains is converted by bacteria in the wood chips into harmless nitrogen gas.

This end-of-pipe measure has been successfully implemented in Denmark and the United States. With this field test, its effectiveness and applicability in Dutch agricultural practice is being examined.

In addition to the wood chip bioreactor in the Vinkenloop catchment area, another bioreactor has been installed in Peelbergen (Limburg, WEnR), and one will also be soon installed in Anna Paulowna (North Holland, Deltares).

Image 1. Installation of the wood chip bioreactor in Westerbeek in Brabant.

Image 2. The wood chip bioreactor being covered.


The wood chip bioreactor is intensively monitored. This monitoring provides insight into the processes that take place in the bioreactor and the extent of the nitrate removal. The course of this conversion of nitrate into nitrogen can be effectively followed through the deployment of various mini-filters at different depths in the wood chip bioreactor. Moreover, the in- and outflow are continuously monitored using nitrate sensors, and samples are taken on a very regular basis.

In order to optimise the operation of the wood chip bioreactor, the volume of water and the speed with which it flows through the bioreactor are also continuously monitored.

Image 3. Mini-filters are deployed at different depths in the wood chip bioreactor.

Nitrate profiles

In addition to the wood chip bioreactor, this project also involves a continuation and supplementation of the monitoring of nitrate leaching that was started during the Water Quality Knowledge Impulse. This monitoring at two fixed measurement points consists of a series of mini-filters, through which the nitrate depth profiles can be followed over time. As a supplement, in the spring of 2024 ‘ad hoc’ profiles are to be measured by means of mechanical drilling. Nitrate depth profiles provide insight into the degree to which denitrification attenuates the passage of nitrate leaching to the deeper subsurface and to surface water. This information contributes to improving nutrient models and identifying land plots sensitive to leaching.