Water use is departing from linear to circular approaches in which wastewater is treated and reused for various purposes such as irrigation, industrial processes, or aquifers' recharge, reducing pressures on the planet's water reserves. The EU has been forging water reuse under its circular economy policy. The transition to a water circular economy (WCE) generates new risks and challenges by introducing new<br> water loops, new communities of users, new responsibilities, different quality standards, and,<br> consequently, new monitoring requirements. Using co-creation processes on the four demo-sites of Project Ô, where new technologies are being implemented for water reuse, this Deliverable assesses the perception of key stakeholders about institutional challenges for water reuse and explores their contributions to innovate policy, planning and institutional arrangements for water reuse. The co-creation process is based on workshops designed to guide stakeholders to identify actions, means, and priorities for implementing the new water loops keeping in mind the institutional set-ups and arrangements in place.