Rivers and Wastewater-Treatment Plants as Microplastic Pathways to Eastern Mediterranean Waters: First Records for the Aegean Sea, Greece

Abstract

The present work provides the first records on microplastic (MP) amounts and types in rivers and wastewater effluents entering the Aegean Sea, eastern Mediterranean. Two rivers were sampled using a manta net (mesh size, 0.33 mm): a small urban and a medium-sized river with a rural, semiurban catchment. MPs in wastewater samples were collected at two wastewater treatment plants (WWTPs) within the Athens metropolitan area after secondary treatment and from a pilot biological membrane unit (MBR), using a series of sieves. MPs in the samples were identified using stereoscopic image analysis and spectroscopic techniques. MP concentrations in the rivers were found to be variable, with as high as 27.73 items m−3 in the urban river. Differences in MP shape types, sizes, and polymer types reflect catchment size and usage. MP concentration in wastewater effluents was found to be 100 times higher in the secondary treatment (213 items m−3) than that in the pilot MBR (2.29 items m−3), with filaments and polymers indicative of synthetic textiles and household use. Further research is needed in order to accurately determine variability in MP concentrations and fluxes from these two pathways in the eastern Mediterranean Sea and elucidate the role of rivers in MP retention.

Distribution Patterns of Floating Microplastics in Open and Coastal Waters of the Eastern Mediterranean Sea (Ionian, Aegean, and Levantine Seas)

“…Recent data on MPs in Kifissos river water further upstream confirm the high level of large MPs and mesoplastics, mostly PE films (Zeri et al, 2021). In addition, the small beach by the river mouth has been characterized as a hot-spot area for beach litter (>10,000 items/100 m) with ∼50% of items corresponding to small sized plastic and polystyrene fragments (Greek Marine Strategy Framework Directive monitoring program, HCMR unpublished data).…”

Influence of Particle Size and Fragmentation on Large-Scale Microplastic Transport in the Mediterranean Sea

“…All modeled MSDs are normalized to the maximum size class, and all measured MSDs are normalized relative to the measured size class closest to 5 mm. The Zeri et al data in panel (c) indicates the size distribution of particles entering the simulation. In panels (a - d), the gray-shaded area indicates particle sizes < 0.33 mm, representing particle sizes below the detection limits of typical Neuston nets used to collect surface microplastics.…”

“…With the fragmentation scenarios, we release 2718 particles per month (97,848 in total), where these are evenly divided over the six size classes. The initial weighing of the particles across the size classes is based on river microplastic size distributions . While the size distribution of microplastics entering the ocean can vary in space and time, ,, we lack the necessary field data to represent such input variability and assume temporal and spatial invariance in the input size distribution.…”

A review of methods for the isolation of microplastics in municipal wastewater treatment

“…Taking into account the variety of sources of MPs, their occurrence has been noticed in all aquatic ecosystems around the world: on the surface of the sea, in deep-sea locations, in coastal and marine sediments, in freshwater, and in river sediments (He et al, 2020;Isobe et al, 2015;Kane et al, 2019;Phuong et al, 2021;Rakesh et al, 2021;Zeri et al, 2021). The presence of MPs in the arctic snowcap has also been noticed, which indicates significant air pollution with MPs and thus the quick and effective transport of MPs throughout the globe (Bergmann et al, 2019).…”

“…Hydrogen peroxide solution can also be used alone. In order to remove organic matter, Zeri et al used 40 cm 3 of 15% hydrogen peroxide per 3 grams of ds and heated the mixture to 40°C for 24 hours (Zeri, 2021). When analysing https://doi.org/10.37705/TechTrans/e2022010 environmental engineering the efficiency of organic matter removal using 30% or 35% H 2 O 2 solution, the samples were immersed in the liquid for 3, 5 and 7 days.…”