Abundance and characteristics of microplastics in municipal wastewater treatment plant effluent: a case study of Guangzhou, China

Wastewater treatment plants (WWTPs) have been proposed as significant sources of microplastics (MPs) in freshwater and estuarine environments. WWTPs, even those with high removal efficiencies, release millions of MPs per plant daily. China is the largest plastic producer worldwide, but only a few studies of MP pollution from WWTPs have been carried out in China. In this work, we present a comprehensive report concerning the MPs in effluent from six WWTPs in Guangzhou, which is the third largest city in China. The six WWTPs employ different treatment processes and serve different populations and types of factories. The average abundance of MPs in the effluents of all six WWTPs was 1.719 +/- 1.035 MP/L. Fiber was the most common type of MP in the effluent, accounting for 39.48 +/- 6.37% of all MPs. Fourier transform infrared spectroscopy confirmed that 35.7% of the particles were plastics, including polyethylene terephthalate (31.9%), polypropylene (26.6%), and polyethylene (9.7%). The results showed that advanced or tertiary treatment technologies could substantially remove MPs and that the size of the population served was positively associated with the abundance of MPs. The number of textile factories was a key factor contributing to the total release of MPs. In addition, the MP shapes and polymer compositions showed that the occurrence of MP types is regional, varies regionally, and is related to the types of factories in the vicinity. More studies on the effects of specific industries are suggested in order to improve the management of wastewater discharge and reduce MPs presence in the natural environment.