Distribution of microplastics in the sludge of wastewater treatment plants in chengdu, China

Large amounts of microplastics can accumulate in wastewater treatment plants (WWTPs), and sludge disposal is suspected to be a major source of microplastics pollution in the environment. It is therefore important to investigate the distribution of microplastics in the sludge of each processing unit of WWTPs. However, little information is available on this topic in China. Accordingly, in this study, the abundance and characteristics of microplastics in the sludge of two WWTPs in Chengdu were investigated. The abundance of microplastics in the sludge samples ranged from 44.4 n·kg −1 to 750.0 n·kg −1 . Microplastics were mainly divided into particles (32.16%), debris (28.14%) and fibers (17.08%) according to their shape, and the colors of the microplastics were mainly green (35.19%) and translucent (18.06%). The particle sizes were mainly larger than 1 mm in dimension. Polyethylene, polypropylene and polystyrene were the prevalent types of microplastics analyzed. Our results provide basic information for better understanding the characteristics of microplastics in sludge and for improving sludge treatment. • MPs in sludges of two typical CASS process WWTPs in Chengdu has been investigated. • Polyethylene, polypropylene and polystyrene were the most common compositions of MPs. • The abundances of MPs in the sludge samples ranged from 44.4 to 750.0 n·kg −1 . • About 68.35% of MPs have a particle size greater than 1 mm.