Closing the water cycle in North-Holland

After medicines are used, pharmaceutical residues end up, via the toilet and the wastewater treatment plants (WWTPs), in surface water. Today’s WWTPs do not specifically focus on the removal of micropollutants. Pharmaceuticals are also transported by river water from other countries into the Netherlands, while other changes impact drinking water sources, such as fluctuating river discharges caused by climate change and the growing use of pharmaceuticals associated with ageing. As a result of the increase of pharmaceutical residues in surface water, initiatives are beginning to get underway in Europe (Switzerland, Germany, France) targeting the removal of pharmaceuticals and other ‘contaminants of emerging concern’ (CECs) at WWTPs. The goal is to prevent these substances from getting into the surface water. The EU has recently added a number of substances, including diclofenac and two hormones, to its Watch List of priority substances (WFD).

A great deal of research is being conducted into effective low-cost removal technologies.

In Switzerland, the government recently decided over the long term to equip an important WWTP with an extra treatment step. Germany and France are also considering taking similar initiatives, while in the Netherlands the problem is receiving more attention.

As soon as the CECs are removed at the WWTP, the water quality of the plant’s effluent will likely be higher than that of the receiving surface water stream. This is positive from an environmental perspective and would improve the ecosystem, but good quality WWTP effluent also opens the door to exploring the possible reuse of this water.


To improve the water quality of WWTP effluent with a view to reusing the water requires an extension of the treatment – among others, CECs and pathogens will need to be removed. The question is what CECs and pathogens are present in the WWTP effluent, and what treatment is needed to render the effluent reusable. Both questions depend on the purpose of the water’s reuse, which could for instance take the form of process water in industrial applications.


In this project we will establish the possibilities for closing the water cycle following the removal of CECs, using proven drinking water technologies, at the Wervershoof WWTP in North Holland. The presence of CECs (including micro- and nanoplastics) in the WWTP influent, effluent and the receiving stream will be monitored. The removal of a number of indicator components will be determined in a pilot installation by means of an innovative combination of ozonisation, followed by ceramic microfiltration and biologically activated carbon filtration. Preliminary ion exchange might be used for purposes of optimisation. The ozonisation will also allow us to determine whether – and, if so, which – oxidation by-products are formed, using bioassays and suspect chemical screening.


In the project, we will explore the possibilities that exist for high-quality reuse in the water cycle following the removal of CECs at the Wervershoof WWTP in North-Holland. Whenever possible, the results will be translated into general conclusions about closing the water cycle through the reuse of WWTP effluent.

In April 2018, the above-mentioned possibilities for closing the water cycle were discussed with the project partners and water laboratories in North-Holland, including the initial contours for a measurement programme at the Wervershoof pilot.