Delfland Water Board and the City of The Hague agreed to initiate research on how purified wastewater can be used as a sustainable heat source. By extracting heat from this water before it reaches the sea, the warmth can be reused . The research will explore how this heat could eventually supply up to twenty thousand homes with renewable heating.
Arjen Kapteijns, Alderman for Energy Transition: “I’m proud of this collaboration with Hoogheemraadschap Delfland. The energy transition in The Hague requires all local sustainable sources. The potential for using treated wastewater is enormous. So, we’re eager to work with Delfland Water Board to further explore where and how we can utilise this heat.”
For Delfland Water Board (in the Netherlands called ‘Hoogheemraadschap Delfland‘), the project fits within its broader mission. As one of the Netherlands’ twenty-two water authorities’, Delfland is responsible for water safety, water quality and water management in one of the country’s most densely populated and economically active regions.
Nieske Dijkshoorn, Hoogheemraadschap Delfland: “Delfland believes it’s important to reduce the use of fossil fuels by switching to sustainable heat sources. The heat in wastewater we treat is one such sustainable source. Delfland is eager to collaborate with regional partners, such as the City of The Hague, to explore how we can utilise this heat source. In this way, we can work together towards a climate-neutral region.”
This technique, aquathermie — is the use of thermal energy from water. By extracting heat from treated wastewater and upgrading it with heat pumps, the temperature can be raised to a level suitable for heating homes and providing hot tap water. Surplus heat generated in summer can be stored underground and reused during colder months, creating a stable, year-round energy source.
The infrastructure required to extract heat from large volumes of water takes up space—something that is scarce in a compact city like The Hague. The study therefore focuses on identifying suitable locations for installations and determining the most effective points along the wastewater pipeline to capture the heat. Residents are already closely involved with the project. If the study confirms the technical and spatial feasibility, the first aquathermal heat from wastewater could become available after 2030.
In 2024 The Hague already opened a sport facility heated with sewage water, saving the city over 170.000 m3 gas per year.
