## 3 Microplastics and Microfibres in DWTPs
As was noted in samples from WWTPs, different factors can affect the analysis and quantification of MPs and microfibres from DWTPs. The most common way of sampling is by storing the samples in containers and then filtering them through sieves of different mesh size [167; 168; 169; 170; 173; 174] or sampling by direct filtration [171; 172; 174]. In order to isolate MPs from impurities, an oxidation of the sample (using only hydrogen peroxide or reagent of Fenton) is conducted, followed by a separation using a NaCl or ZnCl\({}_{2}\) solution [171; 172; 174]. Finally, a visual sorting of MPs is carried out by employing a stereomicroscope [168; 171; 173]; however, [PERSON] et al. (2021) used a fluorescence microscope to differentiate MPs from impurities [172]. As in the case of wastewater and sludge samples, FTIR and Raman spectroscopy are employed as classical techniques for determining the chemical composition of MPs [167; 168; 169; 170; 171; 172; 173; 174]. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Influent**} & \multicolumn{3}{c}{**Effluent**} & \multicolumn{3}{c}{**MNFTS per Day**} \\ \cline{3-11}  & **Tested Water (m\({}^{\star}\)/day)** & **(MPFs/J)** & **\% MFPs/J** & **(MPFs/J)** & **(MPFs/J)** & **\% MFPs** & **(MPFs/J)** & **MPFF/J** & **(DiffFs/J)** & **Affect** & **Effluent** & **References** \\ \hline \multirow{3}{*}{China} & - & - & - & - & - & 440\({}^{\star}\) & 16 & 70.4 & - & - & - & [21] \\ \cline{2-11}  & 12.2 \(\times\) 10\({}^{8}\) & 664 & 64.9 & 4295 & 900 & 66.7 & 620 & 856 & \(52\times 10^{41}\) & \(7.4\times 10^{43}\) & [167] \\ \cline{2-11}  & 1 \(\times\) 10\({}^{8}\) & 2753 & 2 & 605.7 & 351.9 & 50 & 176 & 70.9 & \(64.3\times 10^{41}\) & \(1.8\times 10^{41}\) & [168] \\ \hline \multirow{3}{*}{Crack Republic} & Di: 32.3 \(\times\) 10\({}^{8}\) & Di: 1473 & Di: 11.4 & Di: 168 & Di: 443 & Di: 28.4 & Di: 216 & Di: 25 & Di: \(54\times 10^{40}\) & Di: \(4.0\times 10^{40}\) \\  & Di: 26.8 \(\times\) 10\({}^{8}\) & Di: 2812 & Di: 61 & Di: 211 & Di: 338 & 202 & 23.6 & Di: 22 & 29.2 \(\times 10^{40}\) & Di: \(12.0\times 10^{40}\) & [169] \\ \cline{2-11}  & Di: 78.3 \(\times\) 10\({}^{8}\) & Di: 3805 & Di: 384 & Di: 1325 & Di: 683 & Di: 38.6 & Di: 294 & Di: 78.7 & Di: \(10.0\times 10^{40}\) & Di: \(25.3\times 10^{40}\) \\ \cline{2-11}  & Di: 16.8 \(\times\) 10\({}^{8}\) & Di: 23 & Di: 21.7 & Di: 51 & Di: 14 & Di: 21.4 & Di: 3 & Di: 40 & Di: \(78.7\times 10^{40}\) & Di: \(4.7\times 10^{40}\) \\ \cline{2-11}  & Di: 25.5 \(\times\) 10\({}^{8}\) & Di: 22.166 & Di: 97 & Di: 20.2 & Di: 151 & Di: 27.9 & Di: 12 & Di: 90.4 & Di: \(24.4\times 10^{40}\) & Di: \(24.2\times 10^{40}\) \\ \hline \multirow{3}{*}{Germany} & 2.0 \(\times\) 10\({}^{8}\) & -0.007 & - & - & - & - & - & - & [71] \\ \cline{2-11}  & 3.8 \(\times\) 10\({}^{8}\) & 17.88 & 57 & 10.2 & 2.75 & 54.5 & 1.5 & 85.3 & \(3.9\times 10^{40}\) & \(5.7\times 10^{40}\) & [172] \\ \hline \multirow{3}{*}{Spain} & - & 0.96 & 59 & 0.56 & 0.06 & 56 & 0.03 & - & - & - & [173] \\ \cline{2-11}  & 12.0 \(\pm\) 94 & & DI: 068 & 01: 64 & Di: 01.04 & & & & & & \\ \cline{1-1} \cline{2-11}  & - & Di: 055 & - & - & D2.062 & Di: 22.5 & Di: 20.14 & - & - & - & [174] \\ \hline \hline \end{tabular}  
* Data obtained from the average values of different DWTPs (D \(\geq\) 6) analysed in the study. (MPFs/J) and (MPFs/J) are shown as the mean value, whereas in parentheses the minimum and maximum values found are reported.  
\end{table} 
Table 3: Overview of the incidence of MPs and microfibres in DWTPs. \({}^{8}\)D\({}^{8}\) followed by a number refers to different DWTPs analysed in the cited reference.