A novel methodology to develop EU water reuse risk management plan in agricultural water distribution networks and crop irrigation systems

Treated wastewater (TWW) can be used as an additional water resource to overcome global water scarcity. In response, the EU introduced Regulation 2020/741, which establishes minimum requirements for using TWW in agriculture. In addition, the regulation requires the formulation of a risk management plan for every TWW reuse case and for the entire reuse system. While assessments and management before the outlet of the reclamation facility are well-established, there is limited experience developed for the part of the system beyond the outlet of the reclamation facility. To perform this assessment, new stakeholders (e.g. water distribution managers, storage operators, farmers), previously often overlooked, need to be involved. This study introduces an innovative methodological framework for developing and implementing a risk management plan beyond the outlet of the reclamation facility, focusing mainly on the irrigation distribution network that delivers TWW to its final use in crop irrigation. The approach includes a strategic appraisal using a qualitative method to characterize risks and ensure safe and sustainable water reuse. It also identifies critical nodes within the reuse system, addressing both Human Health Risk Assessment and Environmental Risk Assessment. This methodology was applied on a comprehensive case study in central Italy, where the potential reuse of TWW was assessed for agricultural irrigation in a real 26,000-hectare district. The study represents one of the largest and most complex potential scenarios faced by irrigation managers and operators in Italy. The findings from the risk assessment suggest that the application of tailored, site-specific preventive measures can substantially mitigate associated risks.