Vallei en Veluwe: Can treated wastewater provide new freshwater sources?

For centuries, Dutch water authorities have battled to divert water away from the land. But now, climate change presents an extra challenge – retaining and reusing water to combat increasingly frequent droughts.

The challenge: An increasing risk of drought and flood 

With 1.1 million people spread across 37 municipalities, the region’s residents, farms, and businesses rely heavily on groundwater supplies. But as rainfall becomes less predictable, the water board must address both the risk of flooding and the possibility of supplies running low.

Meanwhile, the 340 million litres of clean wastewater that Vallei en Veluwe produces every day at its 16 water treatment plants is discharged via local rivers and lakes (such as IJsselmeer) into the North Sea. In some cases, wastewater from drought areas is pumped for treatment 40km away.

Unlike rainfall, treated wastewater offers a reliable, 24/7, 365-day-a-year freshwater source – however, this comes with its own challenges to both infrastructure and stakeholder acceptance.

The solution: A new, continuous freshwater source

Today, most water treatment infrastructure is centralised (due to economies of scale), taking effluent away from towns and cities – where it was extracted – instead of treating it locally.

Any new proposals would also need to co-ordinate public and private sector stakeholders with different mindsets. These include industry leaders, agricultural bodies, drinking water companies, and municipalities.

So, in August 2022, we started a project working alongside Vallei en Veluwe to find the best opportunities to reuse treated effluent in drought-prone areas and make recommendations that would satisfy local needs. A group from Vallei en Veluwe worked alongside our Digital Business and Water Technology experts to create a three-stage plan. First, the team created geographic information system maps to visualise the link between demand and supply.

These maps show where the water is most needed, now and in the future – with special attention paid to new housing developments as part of a national plan for one million new homes – and how the wastewater is currently treated and distributed with existing infrastructure.

We identified four potential sites with different requirements, including an industrial area, hillside, and new residential development.

At each of these sites, our team identified different solutions ranging from using effluent from existing centralized treatment plants to installing a single, small-scale treatment plant which could plug into existing infrastructure. The long-term aim is to develop a more circular water system that can accommodate the region’s evolving water needs.

The result: A future-proofed approach for a circular water system and a blueprint for a reliable freshwater source

Using these visualisations, we discussed how the solutions could fit with the water authority’s strategies. This led to a series of workshops with local stakeholders to discuss their requirements, drivers, and barriers to implementation, which are still ongoing.

The final deliverable will be a list of recommendations that provide the biggest societal impact, rather than purely minimizing investment in technology and infrastructure.

The use of treated wastewater would not only create a new, predictable, continuous water source, but also alleviate the pressure on the groundwater which is currently used by drinking water companies, agriculture, and industry.

Potentially, the proposal could also act as a blueprint for a future-proofed approach to water circularity as north-western Europe responds to evolving drought and flood risk.