Microplastics in wastewater treatment plants of Wuhan, Central China: Abundance, removal, and potential source in household wastewater

Abstract

Wastewater treatment plants (WWTPs) are identified as an important source of microplastics (MPs) released into the aquatic environments. The purpose of this study is to compare the abundance and removal of MPs of two WWTPs located in Wuhan City, China, and to evaluate the characteristics of MPs in household wastewater. The results showed that the abundance of MPs in the wastewater of two WWTPs has decreased sharply from 23.3 to 7.9 n L−1 and 80.5 to 30.3 n L−1 with corresponding removal rates of 66.1 and 62.7%, respectively. The fiber, fragment, and microbead present in the three sources of household wastewater (toothpaste, facial cleanser and laundry wastewater) and WWTPs have similarity in shape, and further the main component of MPs in household wastewater and WWTPs is polyvinyl chloride, as is evident from Raman spectrum analysis. Each use of 1 g facial cleanser can release about 1000 MPs, which is higher than that of toothpaste; however, microbeads are only found in the frosting cleanser. An interesting finding is that toothpaste contained fewer amounts of MPs than expected; hence, we observed absence of microbeads in toothpaste. However, over 150,000 fibers are released while washing an average washing of 1 kg of clothing. It has further been estimated that the daily discharge of MPs from household wastewater to WWTPs in China is 9.1 × 1010. Thus, the results indicate that the MPs in household wastewater mainly contribute to the MPs in wastewater of WWTP, therefore, the use of MPs in the personal care products should be banned or alternatives of primary MPs use in these products must be developed.