Transport and accumulation of microplastics through wastewater treatment sludge processes

Wastewater treatment plants (WWTPs) are important routes for releasing microplastics into the environment, with produced sludge acting as a recipient of from wastewater. There is little information on impact processes number in sludge. In this study, presence by Sari WWTP northern Iran was investigated. Samples were taken 3 replications and larger than 37 μm extracted. The primary settling tank, clarifier, after thickener aerobic digester, dewatering contained 214, 206, 200, 238, 129 microplastics/g dry weight, respectively. According to amount each unit, equals 280, 362, 599, 601, 276 million microplastics/day, respectively, which more 85% fibers. numbers output digester did not significantly differ. However, their decreased 50% dewatering, probably due destruction flocs digestive process release attached microplastics, returned wastewater rejected water. Polyester polyethylene predominant types fibers particles, Given annual produced, 100 billion enter environment per year. sludge, therefore, an source emission especially fibers, warranting further evaluation associated environmental hazards.