Quantifying health risks from wastewater reclamation and agricultural reuse using life cycle assessment and quantitative microbial risk assessment

To mitigate the scarcity of freshwater resources, humans have increasingly reused treated wastewater for various purposes, with irrigation accounting for over 70 % of daily water consumption. While wastewater reuse offers a sustainable solution for conserving potable and non-potable water, the reclamation and reuse processes can have environmental and health implications, including greenhouse gas emissions, energy consumption, and pathogen exposure. Life cycle assessment (LCA) has been employed to assess the midpoint and endpoint level impacts, such as human disease burden. Likewise, quantitative microbial risk assessment (QMRA) is a valuable tool for evaluating local risks, such as pathogen exposures during irrigation. Both the LCA (to quantify endpoint indicators of the human burden) and the QMRA tool (to quantify disease burden on human health) use a common metric, disability-adjusted life years (i.e., DALY), which is a measure of overall disease burden that represents the number of years lost due to ill-health, disability, or early death as per person per year (DALYpppy). By combining LCA and QMRA, we can quantitatively measure the health risks associated with wastewater reclamation and reuse. This study aims to estimate the accumulated health burden attributed to the operation of an anoxic/anoxic/oxic/oxic wastewater treatment process and the subsequent reuse of treated wastewater for agricultural irrigation, using the disability-adjusted life years (DALYs). Our findings indicate that the treatment operations contribute a global human health burden of 8.08×10^-7 DALYs per person per year (DALYpppy), while pathogen exposures during irrigation with treated wastewater pose a local health impact of 2.40×10^-2 DALYpppy, emphasizing the importance of wastewater disinfection for reuse.