From Literature Gaps to Integrated Risk Assessment: Unveiling the Complexity of Wastewater Reuse Impact Models

The complexity and inherent interconnection of the reclaimed wastewater (RWW) reuse system requires a thorough assessment of both its positive and negative impacts. In fact, either the reuse is direct or indirect, on one hand, RWW provides essential resources for crops, like water and nutrients, on the other hand, it spreads contaminants that pose potential risks to both human health and the environment. In this context, water utilities and decision makers would benefit from a comprehensive risk-based framework of models aimed at the assessment of its associated impacts. This paper critically reviews the different models that are available for the assessment of RWW reuse impacts, focusing on: (i) the type of impacts, (ii) the evaluated compartments, and (iii) the targeted variables. This review identifies gaps in the evaluation of RWW reuse impacts and outlines future research directions to bridge these gaps. Finally, a simplified approach is proposed for integrating and evaluating three types of risk due to the presence of contaminants of emerging concern (CECs) in RWW for indirect reuse: human health risk, environmental risk and risk related to antibiotic resistance development.