Fate and Control of Microplastics in Municipal Wastewater Treatment Systems

Microplastic pollution is a growing concern around the world due to its negative impacts on the environment and potential implications for human health. Municipal wastewater treatment plants (WWTPs) are a point source of microplastics (MP) that can enter the environment via the discharge of treated effluent and the applications of sludge/biosolids. This chapter presents a summary of the existing knowledge of the fate and transport of MP in sewage treatment systems and the gaps that remain in the understanding of the efficiency of WWTPs in MP control. A recent case study aimed at addressing some of the knowledge gaps is also provided, which involved an investigation into the MP removal efficiency of three WWTPs in Victoria, Australia, with the samplings over two years. The WWTPs under the study included two tertiary systems that utilise conventional activated sludge (CAS) treatment followed by ultrafiltration, one conventional lagoon system and one CAS-lagoon system. The research needs for managing microplastic fibres to improve the overall MP removal by the WWTPs, and further investigations into wastewater lagoon systems for gaining a holistic understanding of the influence of process conditions on MP control by these low-cost and low-energy treatment systems are highlighted. Further research on the risks of the MP of <20 µm and nano-sized plastic materials on environmental and human health and their removal efficiency by WWTPs is also suggested, which must be supported by developed techniques for reliable detection and characterisation of these smaller-sized plastics.