A risk-based framework for comparing the direct and indirect wastewater reuse in agriculture by integrating microbial and chemical risks

The reuse of reclaimed wastewater for irrigation is increasing as a sustainable alternative to freshwater use. However, contaminants persisting in treated effluents pose potential human health risks. These contaminants include chemical pollutants, such as contaminants of emerging concern (CECs) and disinfection by-products (DBPs), as well as microbial pathogens, which can cause chronic and acute toxic effects, respectively. Current risk assessments often evaluate chemical and microbial risks separately, limiting the ability to understand their combined impact on human health. This study presents an integrated risk assessment framework that simultaneously evaluates microbial and chemical risks in both direct and indirect wastewater reuse scenarios. The framework utilizes Disability-Adjusted Life Years (DALY) to compare these risks on a common scale, providing a decision-support tool for risk mitigation and regulatory alignment. Data from a wastewater treatment plant in northern Italy inform the analysis, assessing compliance with wastewater reuse regulations and identifying potential health risks for farmers and consumers. By comparing direct and indirect reuse, this study aims to inform targeted management strategies and policy measures to ensure safe wastewater reuse practices, promoting a regulatory framework that accounts for both planned and unplanned reuse scenarios.