Abundance, characteristics, and removal of microplastics in different wastewater treatment plants in a Yangtze River Delta city of China

Abstract

Microplastics (MPs) have become emerging environmental pollutants worldwide. Wastewater treatment plants (WWTPs) are considered to be the major source and sink of MPs in the terrestrial and aquatic environment. The present study has been carried out for Nanjing, a typical Yangtze River Delta city in China. In this work, the abundance and characteristics of MPs were investigated in the influent of four WWTPs, and the removal effect of different treatment processes was studied in the two advanced tertiary treatment WWTPs. In the influent, the abundance of MPs of industrial WWTPs (IWWTPs) was higher than that of municipal WWTPs (MWWTPs), with a dominant size of 38–63 μm. MP shapes were mainly distributed in fragments and fibers, with polymer species of polypropylene (PP) and polyethylene (PE). In the final effluent, MPs were removed by 93.81 % in IWWTPs versus 88.10 % in MWWTPs, which were mainly influenced by the tertiary treatment technology. The tertiary treatment showed significant differences with the removal efficiency of 61.58 % in IWWTPs, equipped with a high-density sediment tank, and 30.40 % in MWWTPs, equipped with a denitrification filter. This study provides comprehensive information about the MPs' characteristics and fate contained in different sewage of WWTPs and analyzes the tertiary treatment effect of MPs, expecting to provide constructive support for the improvement of management strategies in WWTPs technologies.