Microplastics in Wastewater Treatment Plants (WWTPs): A Review

Microplastics (MPs) in the aquatic environment has recently been documented as an environmental threat due to their negative impact on the ecosystem. Wastewater treatment plants (WWTPs) are expected to be main recipients of microplastics entering into freshwater. Everyday, continuously, treated water containing microplastics from WWTP is discharged in large quantities. The aim of this article is providing a comprehensive knowledge to better understand characteristics of MPs in wastewater, the fate and transport of MPs during treatment process in WWTP, abundance of MPs discharged from WWTP and removal efficiency of MPs in lab scale and existing technologies at WWTPs. The concentration of microplastics varying from 0-91 MP/L (final effluent) and approximately > 32 MP/㎥ in fresh water. Microplastics can be removed in the primary, secondary and tertiary treatment with the removal efficiency were 41%-65%, 0.2%-14% ,and 0.2-14%, respectively. Treated water and sewage sludge act as direct and indirect pollutants into freshwater. The presence of microplastics in the environment has potential as a threat to the aquatic organism (ecotoxicological and ecological risk). Some studies have tried to remove microplastics in wastewater using artificial microplastic with performance with a range of 60-99%. On the other hand, it is necessary to introduce new technology and improve existing technologies in the WWTP that can be correctly used to remove microplastic from wastewater.