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In the last 20 years, several articles related to the use of fluorescence excitation–emission matrices—parallel factor analysis (EEM-PARAFAC) to monitor dissolved organic matter (DOM) in drinking- and wastewater treatment plants were published. Noteworthy, its use in respective quality control laboratories remains scarce. To extend its popularisation, in this work, EEM-PARAFAC was employed to analyse the DOM composition changes along the different stages of the drinking water treatment plant administrated by <i>Società Metropolitana Acque Torino</i>. The best PARAFAC model was the one of three components, indicating that the Po River is constituted, mainly, by humic acid-like (HA-L) and tryptophan-like (Try-L) substances, the tyrosine-like ones being negligible (Tyr-L). Results indicated that physical treatments (sedimentation) did not produce a reduction in the PARAFAC scores; however, a 50% decay in 254 nm absorbance was observed. Fluorescent DOM was only removed with chemical treatments, obtaining ca. 70% HA-L scores decay with ozonation and 40% with chlorination. Furthermore, although ozonation degraded HA-L substances, the Try-L scores increased by 25%, indicating the transformation of HA-L into smaller molecules. On the contrary, total organic carbon measurements only exhibited a significant change when comparing the treatment plant’s inlet and outlet (approximately a 45% decrease), but not within intermediate processes.