Chapter 7 - Occurrence and fate of microplastics in urban water management systems

Abstract

Microplastic (MP) contamination is ubiquitous in global waters and has become a potential health concern to the ecosystem and humans. As the link between the natural and anthropogenic water cycles, urban water management systems, including drinking water treatment plants (DWTPs) and wastewater treatment plants (WWTPs), has been regarded as the transition points of MPs. This chapter summarizes the sampling, separation, and analytical procedures for processing MPs. The classification, source, and transport of MPs in DWTPs and WWTPs are reviewed. Most sampling and separation devices for MPs in water samples are customized based on mechanical screening. Exterior substances on MP particles are removed with pretreatment methods based on chemical digestion and density separation. After pretreatment, Fourier transform infrared and Raman spectroscopy are often used as common synergistic techniques for MP identification. Some semiquantitative methods have been developed to assist in the detection of MPs. In DWTPs, traditional treatments achieved overall removal efficiencies in the range of 39%–95% for MPs in the source water. Preoxidation, disinfection, and advanced treatments induced modifications to the characteristics and behaviors of MPs, implying potential risk for drinking water consumers. Primary and secondary treatments in WWTPs can transport most MPs from WWTP wastewater to sewage sludge. High abundances of MPs occurred in sewage sludge and aging solid waste, while digestion and composting contributed to significant decomposition and reduction of MPs. Because substantial amounts of MPs are discharged along with effluent and/or sludge into receiving waters and/or lands, WWTPs have been confirmed as considerable point sources of MPs to the environment. This chapter provides viewpoints and references for evaluating the risk of MPs after treatments in urban environmental management systems.