Avaliação do desempenho da estação de tratamento de esgotos sanitários da Unisinos no decréscimo de ibuprofeno, diclofenaco sódio e metoprolol

Abstract

In addition to conventional pollutants, emerging contaminants (ECs) such as pharmaceuticals—detected at trace levels (µg/L to ng/L) and not yet regulated by Brazilian environmental legislation—have received increasing scientific and regulatory attention. Due to their persistence and pharmacological specificity, they pose significant challenges to Water and Wastewater Treatment Plants (WTPs and WWTPs), which were not originally designed for their removal. In this context, the present study evaluated, over six sampling campaigns and four monitoring points at the Unisinos WWTP (São Leopoldo Campus, RS, Brazil), the treatment efficiency in reducing the concentrations of pharmaceuticals such as Diclofenac Sodium, Metoprolol, and Ibuprofen. The study also assessed parameters such as COD, TOC, pH, and residual ozone, and compared two analytical techniques for micropollutant detection: UV254 absorbance and Liquid Chromatography. The Unisinos WWTP showed good performance in meeting the standards established by CONSEMA Resolution No. 355 (2017) for pH and COD, with the latter presenting an average removal efficiency above 75%. Regarding pharmaceuticals, influent concentrations of Ibuprofen and Diclofenac Sodium ranged from 21.10 to 987.46 ng/L and 24.58 to 4464.99 ng/L, respectively. Ibuprofen was more susceptible to the applied treatments, with 51.43% removal in the UASB reactor and 65.03% after ozonation. Diclofenac Sodium, on the other hand, showed greater persistence, with only 4.83% removal in the UASB reactor and 35.47% following the ozonation step. Metoprolol was detected in only one sampling event, indicating a low concentration of this compound in the wastewater at the Unisinos WWTP. These findings indicate that the biological processes employed at the University's WWTP are effective in reducing Ibuprofen concentrations, likely due to its higher biodegradability, but appear to be less effective in treating Diclofenac Sodium. The ozonation step showed low efficiency in pharmaceutical removal, suggesting that the current ozone dosage is insufficient. Statistical analyses revealed a strong negative correlation between Diclofenac and TOC, indicating that the pharmaceutical's removal is associated with the reduction of organic load. TOC also showed a positive correlation with COD and UV254 absorbance, reinforcing its role as an indicator of organic matter. Ibuprofen exhibited a moderate correlation with UV254, suggesting that its presence influences absorbance in this spectral range. In contrast, Diclofenac had a weak correlation with UV254, which may be related to its higher resistance to degradation. These results suggest that UV254 monitoring can be useful for the indirect assessment of certain micropollutants, such as Ibuprofen. Overall, the study indicates that while the Unisinos WWTP meets conventional treatment standards, it presents limitations in the removal of persistent pharmaceuticals. The findings highlight the importance of continuous monitoring and the adoption of advanced technologies in the context of environmental sanitation.