Effluent Reuse: European Opportunities for a Resilient Water System

To foster knowledge exchange and cooperation between European countries, Dutch Water Authorities launched a new initiative: a series of webinars with international experts. The first event took place on 20 November at Engage! TV Studio in Amsterdam. The webinar series was kicked off with a webinar on effluent reuse because, while this practice is gaining attention in the Netherlands, countries like Spain and Portugal have already implemented reuse projects on a larger scale. What can the Netherlands learn from their experiences? What challenges did they face, and what advice can they share? Conversely, what insights from the Dutch context might benefit them?

Effluent reuse: technology, challenges and solutions

Rather than focusing solely on technology and success stories, the webinar explored the challenges and solutions surrounding effluent reuse. It was examined how regulations, societal acceptance, and collaboration are key to making this innovation possible. Experts from Spain, Portugal, and the Netherlands shared their experiences:

Spain (Barcelona): Clara Corbella from the Catalan Water Agency shared practical experiences and challenges in using treated wastewater during drought in Barcelona. She shared how effluent is being considered as an alternative water source in a region facing increasing drought.

Portugal (Algarve): Antonio Martins from Águas de Portugal explained how effluent reuse was implemented for irrigation in the Algarve region. He shared how insights from a water reuse program are already underway and how effluent use can be implemented effectively.

The Netherlands (Westerschouwen, Zeeland): Daniëlle Lens, Water Advisor at the Province of Zeeland, presented the Westerschouwen case in Zeeland, highlighting dilemmas such as water pricing and governance roles. She explained that effluent could serve as a source for irrigation, but that roles, responsibilities, and regulations create uncertainty about what the future will look like.

Roundtable discussion

The session concluded with an interactive roundtable discussion, where participants reflected on next steps for the Netherlands and Europe. Panellists included Suzanne Giardina (OmgevingsdienstNL), Sophie Melchers (Utrecht University), and Sandra Sikkema (KWR). Together with the presenters they reflected on the presentations and discussed guiding questions and online audience input. Sikkema shares her thoughts on this subject.

Image: Sandra Sikkema at the table in Engage! TV Studio in Amsterdam.

Regulations and acceptance differ for surface water and reused water

“The roundtable discussion showed that currently there are very strict norms for the reuse of treated effluent in agriculture, even though surface water is also widely used for irrigation. These stricter requirements can hinder the adoption of effluent reuse, despite its potential benefits. Of course, quality standards are essential, but they should not be so rigid that they completely discourage reuse. In fact, it seems inconsistent that surface water—often polluted—is accepted and regulated differently, while effluent faces far more scrutiny. The practice of surface water use for agriculture has become normalized and legitimized over time, whereas effluent remains subject to stricter controls.”

Risk-based approach

At KWR, we emphasize a comprehensive risk-based approach that should apply to every water source, not just effluent. Regulations should ideally be tailored to the intended application and destination rather than the source itself. KWR research on acceptance shows that public support for reuse increases when people understand that “de facto reuse” already exists—meaning water is already being reused through surface water which includes treated effluent. This awareness helps normalize effluent reuse and makes it more acceptable. Beyond the Technological Readiness Level (TRL) of water reuse, we also need to consider the Societal Readiness Level (SRL)—how prepared society is to adopt and integrate a new technology, process, or innovation. SRL complements TRL by focusing on non-technical aspects such as social acceptance, ethical considerations, legal frameworks, and stakeholder engagement. Public and institutional acceptance are critical components; SRL encourages strategies for engagement, transparency, and trust-building. Societal acceptance consists of both public and institutional acceptance.

Public acceptance of reuse generally positive

Within the sector, water authorities often have a high level of acceptance, though they may raise critical remarks. Interestingly, it is often assumed that the public perceives reuse as risky or even scary, but research shows otherwise: public acceptance is generally positive. While initial reactions may include the “yuck factor,” only a small minority would reject or refuse reused water. Public perception is also influenced by institutional attitudes—when employees act as ambassadors, acceptance improves significantly. Other factors that enhance acceptance include transparency about treatment steps, the ability to see or taste the water, and understanding the necessity of reuse. Importantly, there is no one-size-fits-all approach: there is not one “public,” but many different perspectives.

Different client perspectives

At KWR, we segment these perspectives into client perspectives, each group or person requiring a different combination of strategies. Normalization and legitimization occur through pragmatic, normative, cognitive, and regulative strategies, and combining these approaches is key to success.

The way forward: societal acceptance is key

If there is one insight to take away, it is that water reuse is not only a technical challenge, but a societal choice deeply connected to stewardship and justice. In the webinar we have seen that pricing, regulation, and acceptance are interconnected.To move forward, it is essential to develop a clear roadmap that outlines practical steps and priorities. Structured stakeholder consultation should be at the heart of this process, ensuring that all voices, from policymakers to practitioners, are heard and aligned. Equally important is investing in public engagement and trust-building, as societal acceptance is key to the success of effluent reuse initiatives. Finally, fostering cross-sector collaboration will enable knowledge sharing and coordinated action across regions and industries. Water connects us, across borders, generations, and cultures. By approaching reuse with fairness, transparency, and dialogue, we not only address a technical challenge but also strengthen trust and solidarity within society.”

The concept for the webinar series with international experts, organised by the Dutch Water Authorities originated with Petra Goessen from water authority Hoogheemraadschap Hollands Noorderkwartier (HHNK). She manages international relations and is active within the Dutch Water Authorities association. Her vision was to create a platform for international knowledge exchange, where each webinar addresses a different theme and features speakers from across Europe. Paul van der Berg from HHNK and Marina Gaton from Zuiderzeeland Water Authority organized the webinar. Communication was coordinated through the Dutch Water Authorities association and STOWA. You can watch the recording of the webinar here.