Life Cycle Assessment and Comparative Cost Analysis of Removing Contaminants of Emerging Concern from Urban Wastewater by Activated Sludge Treatment and Ozonation

In response to the paradigm shift in urban wastewater treatment that has been driven by emerging regulatory requirements for the removal of chemical contaminants of emerging concern (CECs), it has become essential to evaluate the environmental and economic implications of wastewater treatment upgrades using Life Cycle Assessment (LCA) and comparative cost analysis. The present study evaluates, using full-scale operational data, strategies that can be used in activated sludge systems and downstream ozonation that target CECs and conventional pollutants. Human toxicity, global warming, freshwater ecotoxicity, and freshwater eutrophication were considered midpoint categories, whereas human health and freshwater ecosystems were assessed as endpoint categories, together with a comparative cost analysis. The results show that higher CEC removals mainly reduced freshwater ecotoxicity, although this improvement had a relatively minor effect on the freshwater ecosystems endpoint, which was mostly driven by nutrient emissions. Higher ozone doses reduced the impacts on freshwater ecosystems due to enhanced CEC removal, but increased costs and negatively affected human health, mainly through the impacts of global warming that are associated with electrical energy consumption and oxygen production and transport. Ozonation showed total unit costs of 0.065–0.083 €/m3, and the smallest impacts on freshwater ecosystems under the tested conditions were observed at costs around 0.07 €/m3, corresponding to organic-carbon-normalized ozone doses of approximately 0.8 mgO3/mgC. Integrating LCA and cost analysis supports the identification of environmental–economic trade-offs when selecting wastewater treatment strategies. However, the application of LCA to CEC removal remains limited by the lack of characterization factors for many CECs, which may lead to underestimation of CEC-related impacts, although the magnitude of this potential bias remains uncertain. Further development of CEC characterization factors and site-specific environmental–economic assessment is therefore important to support treatment and regulatory decisions.