Valorisation of non-conventional water resources in cities

Water is becoming increasingly scarce in cities. Climate change, more frequent dry periods, and rising consumption are placing growing strain on existing water supply systems and challenging their long-term reliability. At the same time, large volumes of water are discarded every day as wastewater after a single use, even though this water still contains valuable resources. This is where the RESET research project comes in. RESET aims to make urban water systems more sustainable and resilient by rethinking wastewater not as waste, but as a resource. The project investigates how treated wastewater from households and cities can be safely reused, for example for toilet flushing, garden irrigation, or other applications that do not require drinking water quality. At the same time, valuable nutrients such as phosphorus and nitrogen, as well as usable energy contained in wastewater, are deliberately recovered. At the core of the project is a circular approach: water is intended to be used multiple times, resources are kept within the system, and environmental impacts are reduced. RESET combines nature-based solutions that rely on natural purification processes with technical methods that are applied where particularly high water quality standards must be met. This combination enables flexible, low-energy solutions that can be adapted to different locations. A special focus is placed on decentralised systems, meaning installations that can be operated close to where the water is generated, for example in residential buildings or urban districts. Such solutions relieve central infrastructures such as large-scale treatment plants or pipeline networks and can be tailored to local demand. At the same time, RESET explores how many small installations can be meaningfully interconnected and optimally coordinated with the central supply network so that water availability and demand match in space and time. In addition to technical aspects, the project also addresses safety and public acceptance. Reused water must remain reliably clean, including during storage and distribution. RESET therefore develops concepts for monitoring, control, and quality assurance, as well as clear decision-making tools for municipalities and planners. Through international collaboration, RESET studies these approaches under different climatic and societal conditions. The results provide practical foundations for future-oriented water management and contribute to conserving drinking water, securing resources, and preparing cities for upcoming challenges.