Water Framework Directive: time is running out

Include drinking water goals in approach to nitrogen emissions

Ecohydrologist Arnaut van Loon works at KWR in the areas of restoring groundwater levels, freshwater management and groundwater protection. He says: “To comply with the WFD guidelines for surface-water and groundwater quality, the upper limit for nitrate in groundwater is 50 mg/litre. The Netherlands is required to protect water (including groundwater) intended for drinking water production in such a way that its quality does not deteriorate and to reduce the amount of treatment required for the production of drinking water”.

After an initial decline, the agricultural nitrogen surplus appears to have been increasing again since 2010. That also results in more leaching of nitrate to groundwater. Particularly in the southern and eastern parts of the Netherlands, this means that additional treatment in drinking water production will be required because the soil in that region is naturally susceptible to nitrate leaching.

According to Van Loon, the current situation emphatically requires the inclusion of drinking water objectives in the national approach to nitrogen emissions. “Robust and rapidly implemented measures are needed that also provide farmers with prospects for the future. In this playing field, the National Programme for Rural Areas opens up opportunities to include drinking water objectives in existing measures for nature restoration, water quality and climate adaptation. The required strategy means an approach to agriculture with low emissions that meets all the environmental objectives, including those for the sources that supply our drinking water”.

Figure 1. Nitrate threatens groundwater quality. To maximise crop growth, nitrogen is applied to the soil as a fertiliser and in animal manure. Some of the nitrogen is absorbed by the roots of crops and removed during harvesting. Most of the residue washes out to groundwater as nitrate. That has a negative effect on the quality of groundwater for drinking water production. For drinking water production from surface water, nitrogen is not relevant.

Emerging substances: adequate source approach as the leading priority

The WFD requires new emerging substances that may threaten the drinking water supply to be monitored. When the threshold value of 0.1 microgrammes a litre is reached, risks associated with the substance must be described quickly, including (where necessary) a safe target value for drinking water derived from that description. “Although the drinking water does comply with the standards,” says Inge van Driezum, a researcher in groundwater and surface water quality on the Ecohydrology team, “the amount of treatment required to produce drinking water is increasing.”

“We are finding emerging substances in almost all surface water and bank filtrate, which together account for 40 percent of our Dutch drinking water sources,” continues Van Driezum. In addition, a number of groundwater sources – which supply the remaining 60% – are also threatened in this way. While drinking water companies can still comply with the quality requirements for drinking water, this sometimes involves using more treatment technologies. This is diametrically opposed to the objectives of the WFD.

“To prevent further deterioration in the quality of the groundwater and surface water, action at source has the highest priority, both in Europe and the Netherlands,” says Van Driezum. “This fits in well with basic European principles such as the precautionary principle and the ‘polluter pays’ principle. For this source approach, regulations (including European regulations) will have to be tightened up and adequately implemented within our national borders.”

Figure 2. Groundwater and surface water quality is deteriorating. Water utilities regularly stop the intake of river water from the Meuse and Rhine because the surface water quality is not up to standard due to the presence of ‘emerging substances’: unknown substances for which there are no standards (statutory or otherwise) and for which the harmfulness has not yet been (fully) determined (such as GenX). Emerging substances are also found in groundwater. Drinking water complies with the standards but, if no improvements are made to the sources, producing drinking water will involve more and more treatment.

Highest priority for additional treatment in the fight against pharmaceutical residues

Thomas ter Laak, senior researcher in Chemical Water Quality at KWR, talks about developments relating to pharmaceutical residues in the water chain. “Every year, about 190 tonnes of pharmaceutical residues enter our surface water in human urine and faeces. This amount is increasing in line with medicine consumption in the Netherlands. More and more medicines are being added to the mix as well. Despite treatment at wastewater treatment plants, pharmaceuticals enter the water chain. That is a particular concern during dry periods because that is when the proportion of waste water in most surface waters increases, and therefore the concentrations of pharmaceutical residues increase as well.”

With extensive monitoring, a threshold for pharmaceutical residues of 1 microgramme a litre, and good drinking water treatment, drinking water quality is not currently at risk. But to maintain that situation in the future, more action is needed.

Figure 3. The levels of pharmaceuticals from production, use and the water chain to drinking water fall from 100% to less than 1% and then, as a result of drinking water treatment, a long way below the risk thresholds.

The biggest gain in terms of surface water quality can be achieved with additional treatment at wastewater treatment plants, where pharmaceutical residues from households and healthcare facilities meet, Ter Laak believes. “This is also the most practical operational option. However, this means that the water authorities have to act, even though they do not cause the emissions. On the basis of the ‘polluter pays’ principle – which is part of a stricter European Commission directive that is expected to take effect in 2024 – producers, the medical sector and households will have to contribute.”