Improved methodology to determine the fate and transport of microplastics in a secondary wastewater treatment plant

Presence and fate of microplastics in the water sources: focus on the role of wastewater and drinking water treatment plants

“…Moreover, fragments appeared to be removed more than fibers: the authors noticed indeed an increase in relative abundance of fibers after secondary treatments, followed by a decrease in higher size MPs classes, even if with some exceptions [67]. Lower removal of fibers by secondary treatments was indeed confirmed also by recent papers [85,89]. Park et al [82] found a higher relative abundance of fibers in the effluent as compared to the influent.…”

“…The mean size increased a little in the effluent [85]. Raju et al [89] noticed how PET and PS were the most abundant in sludge compared to other low-density polymers, confirming the role of density during separation by sedimentation. The different removals reported by the various papers can be related to the various secondary treatments and operational conditions applied in the plants, and the different size and types of MPs.…”

“…Regarding MPs size, Sun et al [67] reported how often the fraction >500 μm was the most present. Raju et al [89] found instead increasing frequency with decreasing size range, with highest percentage within 1.5− 38μm: often overlooked lower size classes could indeed contain more MPs. Finally, Simon et al [78] found that the influent concentration of MPs to 10 WWTPs was not normally distributed in terms of particle numbers nor of mass; however, they did not deepen the understanding of the differences among the WWTPs.…”

Factors affecting microplastic retention and emission by a wastewater treatment plant on the southern coast of Caspian Sea

“…), extraction methods (digestion method and salt used for density separation), identification methods, and social, economic and climate conditions. This makes it difficult to compare the results of different studies (Avio et al, 2015;Raju et al, 2020), and emphasizes the importance of developing standard protocols for the measurement and reporting of MPs to facilitate the comparison of data.…”

“…The reason for the removal of most particles smaller than 500 mm and the small amount of fibers (which were not removed during primary settling) in the clarifier tank may also be due to the formation of biofilms, which increased their density (Carr et al, 2016;Raju et al, 2020), or their adhering to the bioflocs formed in the aeration tank which settled in the clarifier (Turovskiy and Mathai, 2005;Zhang et al, 2020).…”