Characterization of metoprolol biodegradation and its transformation products generated in activated sludge batch experiments and in full scale WWTPs.

Metoprolol (MTP) is a compound of concern, considered as an emerging contaminant due to its high consumption, pseudopersistence and potential ecotoxicity. Activated sludge batch experiments were performed to evaluate the biological transformation of MTP and the formation of transformation products under different treatment conditions. Total MTP removal was obtained in aerobic conditions, and the formation of MTP known metabolites (metoprolol acid (MTPA), α-hydroxymetoprolol (α-HMTP) and O-desmethylmetoprolol (O-DMTP)) and unknown transformation products (TPs) was investigated. The three known metabolites and two new TPs generated along the experiments were identified by liquid chromatography coupled to high resolution mass spectrometry. For the two new TPs plausible structures were proposed based on the tentative identification. MTPA had the major ratio formation for the TPs identified along the experiments (up to 40% of initial MTP concentration after 96 h treatment) and its persistence through biological treatment was proven. Ecotoxicity studies using Vibrio fischeri bioluminescent bacteria in an acute toxicity test showed that MTP and its known TPs are not toxic with the exception of o-DMTP. Finally, MTP and its TPs were monitored in a full scale membrane bioreactor and in a full scale conventional urban wastewater treatment plant (WWTP) and the results were compared with those obtained in batch experiments. α-HMTP was detected for the first time in a WWTP influent whereas MTPA was detected in influent and effluent WWTP samples at much higher levels (up to 100 folds higher) than MTP itself remarking its high persistence.

Pharmaceuticals occurrence in a WWTP with significant industrial contribution and its input into the river system.

Occurrence and removal of 81 representative Pharmaceutical Active Compounds (PhACs) were assessed in a municipal WWTP located in a highly industrialized area, with partial water reuse after UV tertiary treatment and discharge to a Mediterranean river. Water monitoring was performed in an integrated way at different points in the WWTP and river along three seasons. Consistent differences between therapeutic classes were observed in terms of influent concentration, removal efficiencies and seasonal variation. Conventional (primary and secondary) treatment was unable to completely remove numerous compounds and UV-based tertiary treatment played a complementary role for some of them. Industrial activity influence was highlighted in terms of PhACs presence and seasonal distribution. Even if global WWTP effluent impact on the studied river appeared to be minor, PhACs resulted widespread pollutants in river waters. Contamination can be particularly critical in summer in water scarcity areas, when water flow decreases considerably.