Using excitation-emission matrix fluorescence to evaluate the performance of water treatment plants for dissolved organic matter removal

Behaviour of the fluorescence peaks throughout the stages of the wastewater treatment plant (WWTP) of Burgos (Spain). [Display omitted] •The main peaks in the domestic wastewater are the protein-like T2 and the fulvic-like A.•Peak T1 shows the highest total removal in the WWTP.•Humic-like peaks are mostly removed by decantation whereas peak T1 by biodegradation.•A poor correlation was obtained between peak T2 fluorescence and COD, BOD.•The majority peak A of the reservoir water is completely removed in the DWTP. This study is aimed at assessing the performance of water treatment plants (both wastewater and drinking water treatment plants) for dissolved organic matter (DOM) removal using excitation-emission matrix fluorescence (EEMF) as the monitoring technique. The influent from the wastewater treatment plant (WWTP) of Burgos (Spain) is characterized from the presence of protein-like peaks (T1 and T2) and humic-like peaks (A and C), T2 and A showing the highest fluorescence intensity. The percentages of total removal in the effluent were in the following order: peak T1 (65%) > peak A (45%) > peak C (34%) > peak T2 (26%). The humic-like peaks were the most removed at the primary sedimentation stage, whereas peak T1 was by far the most removed in the biological reactor. Protein-like peaks T1 and T2 experienced a slight increase in the final effluent in comparison to their fluorescence at the previous stage (the exit of the biological reactor), an increase that can be explained by the release of SMP (soluble microbial products) from the biomass in the secondary clarifier. A poor correlation was obtained between peak T2 fluorescence and COD, BOD (r2 = 0.34–0.38). The natural water from the Úzquiza reservoir in Burgos (Spain) is characterized by the only presence of humic substances: a majority peak A (fulvic-like) and a weak peak C (humic-like). The whole fluorescent DOM was removed by coagulation-flocculation but a low fluorescence peak T2 appeared at the final stage, coming from protein-like SMPs released by the biomass attached to the filters.