Innovative Standards for Using Nature-Based Solutions in Water Reuse Projects

Water reuse is increasingly recognized as a key element in sustainable water resource management, yet its implementation faces technical, economic, and social challenges. The Can Cabanyes project in Granollers (Catalonia, Spain) offers a pioneering example of a hybrid water reuse system that combines nature-based solutions with a technical reclamation plant and a distribution network. Over two decades of operation, the system has demonstrated reliable removal of conventional pollutants, pathogens, and certain emerging contaminants while also revealing seasonal patterns linked to temperature-dependent nitrification. Beyond water quality improvements, the project has generated significant ecological and social benefits, including habitat restoration, biodiversity enhancement, and recreational opportunities, all of which contribute measurable positive externalities that outweigh private costs.Drawing from this long-term experience, a set of innovative standards is proposed to guide the replication of hybrid systems. These include integrating green and grey infrastructure, adopting adaptive management practices, implementing rigorous performance monitoring, valuing externalities in economic assessments, and ensuring transparent stakeholder engagement. Together, these principles establish a robust framework for designing resilient and socially accepted water reuse projects. The Can Cabanyes case illustrates how nature-based solutions can be strategically embedded within peri-urban contexts, advancing both environmental sustainability and water security.