Spatiotemporal Distribution Characteristics and Removal Efficiency of Microplastics in a Wastewater Treatment Plant

Abstract

This study examined the removal efficiency of microplastics (MPs) in a wastewater treatment plant (WWTP) in Zhengzhou, China. A three-point sampling approach (influent, process effluent, and final effluent) was employed, with samples collected across three seasons (summer, winter, and autumn) to investigate seasonal variations in MPs. The abundance of MPs in influent ranged from 184.3 ± 4.0 to 145.3 ± 24.0 n/L, while in the process effluent it decreased to 79.3 ± 18.7 to 62.3 ± 15.0 n/L. Furthermore, in final effluent it was further reduced to 26.0 ± 7.0 to 38.7 ± 5.1 n/L. Fragments and granule-shaped MPs predominated (>80%), with polypropylene (PP, 42.6%) and polyethylene terephthalate (PET, 31.8%) emerging as the dominant polymer types. The removal efficiency of MPs in the WWTP was 86%, 81%, and 73% in summer, autumn, and winter, respectively. Additionally, the plant exhibited differing removal efficiencies for MPs of varying sizes. Notably, residual sludge retained substantial MPs loads, with seasonal abundances measuring 22.3 ± 3.2, 14.2 ± 2.4, and 29.1 ± 6.7 n/g in summer, autumn, and winter samples, respectively. The findings underscore the importance of implementing effective management strategies and interventions in wastewater systems to mitigate MP pollution.