Microplastics in Municipal Wastewater Treatment Plants: Practical Monitoring Standards and Full-Scale Removal Performance

Abstract

Microplastics (MPs) are increasingly being detected in municipal wastewater treatment plants (WWTPs), from which they are partially removed, transferred to sludge, or discharged with treated effluent. Although research on microplastics in aquatic environments has grown rapidly, clear and practical guidance for wastewater utilities regarding consistent monitoring methods and realistic full-scale removal performance remains limited. This review provides a practice-focused overview of MPs in municipal WWTPs by summarizing monitoring approaches and evaluating full-scale removal performance across major treatment stages, including primary clarification, activated sludge treatment, secondary clarification, tertiary filtration, and membrane systems. The review highlights the wide variation in reported removal efficiencies and explains how differences in sampling methods, particle size ranges, and analytical techniques affect performance. It also examines solid-phase transfer, key removal mechanisms, and operational factors that influence treatment performance, with particular attention paid to the accumulation of MPs in sludge and biosolids. Instead of emphasizing lab-scale technologies, this paper discusses how microplastic control can be integrated into existing solid management practices and broader emerging contaminant management strategies. Overall, this review provides practical guidance for wastewater operators, engineers, and decision makers on managing MPs within existing treatment infrastructure and real-world operational constraints.