Microplastic emission trends in Turkish primary and secondary municipal wastewater treatment plant effluents discharged into the Sea of Marmara and Black Sea.

Wastewater Treatment Plants (WWTPs) are recognized as one of the primary sources of microplastics, a class of contaminants that has lately gained attention. The quantity of MP that WWTPs release into the environment depends on several factors, including the treatment type, season, and population serviced. MP abundance and characterization were explored in 15 WWTP effluent waters, 9 discharged to the Black Sea from Türkiye and 6 to the Marmara Sea, with varying population densities and treatment methods. The mean MP abundance in primary treatment WWTPs (76.25 ± 49.20 MP L-1) was found to be substantially greater than that in secondary treatment WWTPs (20.57 ± 21.56 MP L-1) (p<0.05). MPs in WWTP effluent waters showed significant seasonal and spatial differences (Two Way ANOVA, Tukey, p<0.05). However, no positive correlation was detected between the population serviced and MP abundance in effluent waters. While the fiber was the dominant shape (49.5%) among MPs in effluent waters, ≈80% of the length was <1000 µm. MPs are classified into polymer types as follows: polyethylene terephthalate (34.9%) > polypropylene (32.4%) > polyethylene (19.9%) > polyamide (11%) > polystyrene (1.2%) > polyvinyl chloride (0.6%). With effluent waters from the WWTPs tested, we calculated that 1.24x1010 daily MPs are discharged into the Black Sea while 4.95x1010 MPs are into the Marmara Sea, for a combined annual discharge of 2.26x1013 MPs highlighting that WWTPs are key contributors of MP in Turkish coastal waters.

The impact of the marine sewage outfalls on the sediment quality: The Black Sea and the Marmara case.

Marine sewage outfalls are the cheapest method of disposal for municipalities with restricted funds, despite their negative effects on marine ecosystems. This study was conducted on the marine sewage outfalls of the Turkish cities Rize (Black Sea) and Yalova (Sea of Marmara). Heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) were investigated in the sediments for determine pollution degree. Two of Yalova stations were classified as having high contamination levels (1034.436 and 1476.483 ng/g, respectively) and all the other stations suffered moderate pollution in terms of ∑16PAHs. ∑DTTs in sediments above probable effect levels (PELs), were observed both stations Yalova and Rize. The highest metal concentrations in the sediments from the eight stations ranged from 4.97 to 29.65 mg/kg for Ni; 7.57-44.14 mg/kg for Cr; 9.84-42.76 mg/kg for Cu; and 48.08-103.77 mg/kg for Zn. In sum, examination of pollutant sources provides clear evidence of an anthropogenic effect on the discharge environments.