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The Paradox of Microplastic Removal in WWTP: Redistribution of Micropollutants in the Environment

Current Pollution Reports 2025 5 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Agata Zdarta, Guoqiang Li

Summary

This review examines the paradox that wastewater treatment plants, while removing microplastics from water, may actually contribute to their degradation and fragmentation through mechanical and chemical processes. The study found that treatment stages involving physical abrasion, advanced oxidation, chlorination, and ozonation can break microplastics into smaller, potentially more harmful particles that may be redistributed into the environment.

Study Type Environmental

High amounts of microplastics (MPs) are collected and then disposed of in sewage treatment plants. This review aims to identify the effects of wastewater treatment processes on the physical and chemical properties of MPs as well as their fragmentation and ageing, which are rarely reported and have not yet been revised. The amount of microplastic particles introduced into the WWTP depends on many factors, such as the area and population, treatment processes, migration of people, and weather conditions. As a result, WWTP effluents were identified as the source of MP pollution. Selected treatment methods and chemicals used in wastewater treatment may contribute to the deterioration of MP. The impact of individual physical, mechanical, and chemical factors on the fate of microplastics in the WWTP was analysed. In the case of preliminary and primary treatment processes, the fragmentation of MP particles is mainly affected by mechanical interactions such as physical abrasion and water shearing force. However, during tertiary treatment processes, chemical factors such as advanced oxidation processes, chlorination, and ozonation play a leading role in MP deterioration. The paradox of so-called microplastic removal in WWTPs has been highlighted, and the concept of defining wastewater treatment plants as sources of tertiary microplastic pollution has been proposed.

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