## 3 Results and Discussions
In terms of morphology, MPs are primarily categorized into fibers, shafts, films, flakes, and spheres. The results of the conducted research also indicate that the largest percentage of MPs are fragments in the samples from May, June, and July (Figure 5). Similarly, in this work (Figure 5), fibers and fragments represented the highest proportion of MPs [20; 30; 31], unlike the work of [PERSON] et al., which found that MPs are mainly composed of polyolefin (fibers and rollers), acrylic fibers (fibers), polyethylene (films), polyamide (films), alkyd resin (flakes), and polystyrene (balls) [22]. However, completely different results were obtained by [PERSON] et al. (2017). They found that the types of MPs in sediments included beads (37.6%), flakes (31.8%), and fibers (28.9%) [32]. Figure 5: The amount of MPs divided into black and colored fragments and fibers, depending on the month. The size of MPs were fractions greater than 300 \(\upmu\)m, which were identified in July (an average of 2351 fractions per 100 g from dry matter of stabilized sewage sludge) and in June (an average of 2157 fractions) (Figure 6). Samples from May exhibited a size of up to 1500 \(\upmu\)m (average 1376 fractions). Fractions up to 300 \(\upmu\)m constituted a significant minority. In this case, these were the most common in June (an average of 418 fractions) and May (an average of 184 fractions) (Figure 6). A certain trend can be noticed. Larger microplastic fractions (>300 \(\upmu\)m) dominated in samples from July (2351 fractions per 100 g of dry weight of sediment) and June (2157 fractions), while samples from May contained fewer of these larger fractions (1376). In turn, smaller fractions (<300 \(\upmu\)m) were the minority in each sample, but their number was the highest in June (418 fractions) and May (184 fractions). It can be seen that larger fractions dominated, especially in the summer period (June-July), and the number of smaller fractions varied more over time. In wastewater, in the sewage sludge from which MPs originate, dimensions of 25 \(\upmu\)m, 100 \(\upmu\)m, and 500 \(\upmu\)m were used most often for size classification [33; 34; 35]. Analysis of the literature shows that, on average, more than 90% of MPs in wastewater are less than 500 \(\upmu\)m in size, and in some samples, approximately 60% of MPs were smaller than 100 \(\upmu\)m [36; 37]. MPs separated from stabilized sewage sludge displayed the highest LDPE content. Figure 7 shows the most frequently obtained spectrum during ATR-FTIR analysis (Figure 7). The intensity at 3340 cm\({}^{-1}\) is responsible for CH stretching vibration =C-H [38]. The bands around 2918 cm\({}^{-1}\) are responsible for C-H stretching vibrations, typical for pure polyethylene. Peaks between 2840-2950 cm\({}^{-1}\) indicate both symmetric and asymmetric CH stretching vibrations [39]. The intensity at 1744 cm\({}^{-1}\) indicates the presence of carbonyl group stretching C=O [40]. The same is true for the peak at 1622 cm\({}^{-1}\), which indicates the C=O group coupled to the C=C group derived from the vinyl group [41; 42]. The band at 1562 cm\({}^{-1}\) comes from the vibrations of the C=C group. Vibrations at 1460 cm\({}^{-1}\) are C-H deformation vibrations and demonstrate the crystallinity of polyethylene. In the case of high-density polyethylene (HDPE), there would be a multiplicity of peaks. Peaks at 1385 and 1353 cm\({}^{-1}\) are indicative of polymer branching, which is typically found in LDPE [43]. The B-Bands at 1244 1243 are visible, which indicates the content of oxygen compounds. They can also be derived from phthalates and other fillers and plasticizers. The peak at 1028 cm\({}^{-1}\) can be responsible for oxygen bonds (C-O, C-OH) [38]. During the analysis of the literature sources, it was discovered that more than 30 types of microplastic polymers are detected in wastewater and wastewater treatment plants. The most common polymers were polyester, polyethylene, polyamide (PA), polyolefin, acrylic, and others.