Environmental impact of microplastic emissions from wastewater treatment plant through life cycle assessment

This study aimed to quantify the environmental impact of microplastic (MP) emissions from wastewater treatment plants (WWTPs) using life cycle assessment (LCA). The investigation comprehensively evaluated the contribution of MPs to overall WWTP midpoint and endpoint impacts, with a detailed analysis of the influence of particle size, shape, polymer type, and the environmental costs and benefits of individual wastewater treatment processes on MP removal. The LCA model was developed using SimaPro software, with impact assessments conducted via the USEtox framework and the IMPACT World+ methodology. Results showed that at the midpoint level, MPs accounted for 1.24E+05 CTUe (94 % of the total plant impact), representing the potential harm to aquatic species per cubic meter of discharged wastewater-surpassing the impacts of other contaminants (e.g., heavy metals, nutrients) by at least two orders of magnitude. At the endpoint level, the damage of 8.39E-02 PDF·m²·yr (1.7 % of the total) indicated the potential loss of species diversity, comparable to other pollutant contributions. Polyethylene, polystyrene, and polypropylene were identified as the most impactful polymer types. In terms of environmental costs and benefits, secondary, tertiary, and primary treatments demonstrated decreasing environmental benefits, directly correlated with their respective MP removal efficiencies. These findings underscore the critical role of MP emissions in WWTP life cycle inventories and highlight the urgent need for targeted environmental policies and advanced treatment technologies to address MP contamination in both natural and engineered aquatic systems.