Levels and sources of microplastics and phthalic acid esters in sewage sludge from wastewater treatment plants in the Marmara region of Turkey

In recent years, microplastics (MPs) have become pervasive environmental pollutants globally. Phthalic acid esters (PAEs), commonly used as plasticizers, are frequently associated with MPs. Investigating the fate of these pollutants before their release and their presence in sewage sludge is crucial for understanding their impact in different wastewater and water treatment plants (WWTPs and WTPs).This study analyzes the distribution of MPs in terms of abundance, size, shape, and color, as well as the concentrations of 13 distinct types of PAE, in sludge samples collected from 18 treatment plants located in a densely populated and industrialized region. The findings showed that 68 % of the MPs detected in the sludge samples were fragments, 27 % were films, and 5 % were fibers. The most common MP color was white-transparent, yellowish, and the most prevalent MP types were polyethylene (PE), polypropylene (PP), and polyethylene tereftalat (PET). MP concentrations were found to be 4726 ± 2939 MP/g (dry weight (dw)) in sludge from industrial WWTPs (IWWTPs), 6078 ± 695 MP/g (dw) in sludge from urban WWTPs (UWWTPs), and 2133 ± 1690 MP/g (dw) in sludge from drinking WTPs (DWTPs). The PAE concentrations were measured at 10477 ± 10291 µg/kg in sludge from IWWTPs, 23475 ± 10258 µg/kg in sludge from UWWTPs, and 4127 ± 4382 µg/kg in sludge from DWTPs. According to Principal Component Analysis (PCA), the primary source of PAEs in the sludge samples was the cleaning and personal care products, contributing 41 %, followed by industrial applications at 22 % and household goods at 11 %.