Microplastic Composition, Load and Removal Efficiency from Wastewater Treatment Plants Discharging into Orontes River

Wastewater treatment plants (WWTPs) are the last stop for microplastic particles generated by anthropogenic activities before they enter the aquatic environment. In this study, three WWTPs discharging into Orontes River were investigated in terms of microplastic (MP) composition, microplastic abundance, treatment and load. Two of the WWTPs apply secondary treatment with activated sludge system and trickling filter, whereas the last WWTP apply tertiary treatment with a membrane bioreactor. When all data are combined, mean MPs abundance in the influent and effluent samples were found as 57.2 MPs/L and 2.1 MPs/L, respectively. The highest MPs removal was achieved by the membrane bioreactor (99%) and followed by the trickling filter (98%) and activated sludge process (91%). In terms of composition, fibers were dominant in both influent (94%) and effluent waters (94%). Common size of MPs in the influent waters was 500–1000 µm and decreased to < 500 µm after treatment. Polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET) are the main polymers and account for 77% of sampled MPs. Even though the MPs removal rate is significantly high, approximately 45 million of MPs discharged from WWTPs into Orontes River every day. For this reason, examined WWTPs could be considered as a point source of MPs and could harm the water quality and aquatic biota.