Controlling Microplastics in Urban Wastewater Treatment Plants: A Policy Brief

Abstract

Background: Microplastics, defined as plastic particles smaller than 5 mm, are persistent environmental contaminants that enter urban wastewater through domestic, industrial, and urban runoff sources. Conventional wastewater treatment processes do not completely remove microplastics, allowing them to reach receiving waters and potentially affect ecosystems and human health. Objectives: This article examines the role of urban wastewater treatment in mitigating microplastic pollution, with particular attention to the Iranian context and to densely populated or industrialized areas such as Zahedan, and proposes policy and management approaches to strengthen pollution control. Methods: A policy-oriented review of the available evidence was conducted to assess the persistence of microplastics across conventional wastewater treatment stages and to evaluate technical, regulatory, institutional, and source-control measures for reducing their environmental release. Results: Evidence indicates that microplastics can persist through standard wastewater treatment processes and remain in treated effluents and associated residuals, thereby contributing to ongoing environmental dispersion. Consequently, current treatment capacity is insufficient to fully address the scale of microplastic pollution. Effective mitigation requires advanced treatment technologies, source-control measures, enforceable effluent standards, improved monitoring, institutional coordination, and greater public awareness. Conclusions: Microplastic pollution is a growing, unresolved environmental challenge that cannot be adequately addressed through conventional wastewater treatment alone. An integrated framework combining technical, regulatory, institutional, and societal interventions is required to reduce microplastic discharge, protect ecosystems and public health, and support sustainable wastewater management.