2 september, 2025
Interview Thijs Blom, data analyst at RIWA-Meuse: “This tool gives us an insight into the s... kopie
Which harmful substances have been present most in the river water in the Meuse basin in recent years and where? Also, what is the best way to analyse these trends to be able to tackle the presence of the pollutants in question? Four trainees from the National Water Traineeship developed a tool for this purpose.
The River Meuse is a crucial source of drinking water for more than 7 million residents in the Netherlands and Belgium. Discharges of substances that do not degrade, are difficult to remove during water treatment, and are harmful to both human health and the environment place increasing pressure on drinking water supplies.
According to Maarten van der Ploeg, Director of RIWA-Maas, “The Meuse is particularly vulnerable to discharges of harmful substances during periods of low river flow. Due to climate change, low-flow conditions are expected to occur more frequently and persist for longer periods. It is precisely under these circumstances that additional protection is needed.”
To assess whether this protection is adequately reflected in discharge permits, RIWA-Maas recently commissioned an independent study.
Discharge Permits Are Insufficiently Climate-Resilient
The study shows that the method currently used in the Netherlands to protect river water from pollutant discharges is not adequate in practice. Under the current approach, a discharge is required to comply with surface water quality standards for 90% of the year. During periods of low river flow—which are assumed to occur during the remaining 10% of the year—compliance is not necessarily required.
In reality, however, low-flow conditions can persist for much longer periods during dry summers. As a result, discharges may have a greater and more prolonged negative impact on water quality than anticipated when permits are issued. From a drinking water perspective, this is highly undesirable.
RIWA therefore calls for a revision of this assessment methodology and for a substantial tightening of requirements relating to hazardous substances.
Incidents and PFAS Discharges
Recent events highlight the urgent need to strengthen the protection of river water quality.
In August, a discharge of the pesticide propamocarb occurred near Liège. Concentrations were so high that Waterleiding Maatschappij Limburg (WML) was forced to suspend its intake of Meuse water. As a result, the river remained unsuitable for drinking water production in the Netherlands for an extended period.
In July, a draft permit was published authorising the discharge of industrial wastewater containing PFAS—substances classified as Substances of Very High Concern (SVHCs)—into the sewer system in Weert. This wastewater ultimately enters the Dutch section of the Meuse, with potentially far-reaching consequences for both the environment and society.
Permits for such discharges are granted more frequently than many realise and run counter to the fundamental principle that pollution should be addressed at its source.
Transparency as a Prerequisite
According to RIWA, it is essential to obtain a comprehensive overview of the substances that companies discharge into the Meuse basin through their wastewater. A key requirement is the inclusion of an expiry date in all discharge permits. This would ensure that, upon permit renewal, authorities verify which substances are actually being discharged and assess whether those discharges remain acceptable during periods of low river flow.
In the Netherlands, little to no information is available on companies that discharge waste substances through municipal sewer systems. In contrast, such information is often available in Flanders.
Van der Ploeg states: “RIWA calls on Dutch municipalities and provincial authorities to take their duty of care seriously and provide this transparency. It is essential that competent authorities make every effort to prevent emissions of hazardous substances. Without such commitment, effective protection of the Meuse as a drinking water source for 7 million people will be impossible.”
About RIWA-Maas
RIWA-Maas represents the interests of drinking water companies in the Netherlands and Belgium that collectively abstract approximately 500 billion litres of water from the Meuse each year to produce drinking water for around 7 million customers. This drinking water is supplied to consumers in and around Rotterdam, The Hague, Brussels, Antwerp, parts of Limburg, Zeeland, and West Flanders. The stringent quality standards that drinking water must meet require a preventive approach to the protection of surface water resources.