Implications of the transition towards water-wise approaches in urban areas: elucidating the risk from micropollutants release

The transition towards circular and sustainable urban water systems, embracing a water-wise city approach, results in highly interconnected systems, introducing complexities in managing water quality due to the intricate interplay of pollutant sources, pathways, and receptors in urban environments. This study focuses on assessing the impact of transitioning to a water-wise city approach on water quality. The analysis employs an integrated model-based approach to evaluate the release of micropollutants (PFOA, PFOS, pyrene) in the urban water system, considering potential future changes. We considered Milan (Italy) as a case study and explored sustainable urban water management strategies related to the hydraulic reconnection of canals, including (i) the use of groundwater for energy purposes, (ii) the establishment of a separate stormwater sewer system, and (iii) the indirect reuse of reclaimed water for crop irrigation. Acute and chronic environmental risks were assessed at various locations of the recipients, under different water management and climate change scenarios. Uncertainties on projections related to rainfall and runoff concentrations were also considered. The model accurately predicted average micropollutants concentrations in the current situation. PFOA and PFOS exhibit chronic, but not acute risks in all scenarios; high removal efficiency is required to reduce the risk at acceptable levels. Pyrene poses higher risks for increasing separation fractions of the sewer system, with further increase for climate change, but concentration uncertainty has more influence than precipitation uncertainty on the risk extent. This study provides a water management framework, identifying critical sources and locations under current, future, and climate change scenarios.