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Ozone oxidation of antidepressants in wastewater –Treatment evaluation and characterization of new by-products by LC-QToFMS

André Lajeunesse1, Mireille Blais2, Benoît Barbeau2, Sébastien Sauvé3 and Christian Gagnon1*

Author Affiliations

1 Environment Canada, Wastewater and Effluents Section, Water Science and Technology Directorate, 105 McGill Street, Montreal, Quebec, H2Y 2E7, Canada

2 École Polytechnique de Montréal, Department of Civil, Geological and Mining Engineering, P.O. Box 6079, Succursale Centre-ville, Montreal, Quebec, H3C 3A7, Canada

3 Department of Chemistry, Université de Montréal, P.O. Box 6128, Succursale Centre-ville, Montreal, Quebec, H3C 3J7, Canada

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Chemistry Central Journal 2013, 7:15  doi:10.1186/1752-153X-7-15

Published: 25 January 2013



The fate of 14 antidepressants along with their respective N-desmethyl metabolites and the anticonvulsive drug carbamazepine was examined in a primary sewage treatment plant (STP) and following advanced treatments with ozone (O3). The concentrations of each pharmaceutical compound were determined in raw sewage, effluent and sewage sludge samples by LC-MS/MS analysis. The occurrence of antidepressant by-products formed in treated effluent after ozonation was also investigated.


Current primary treatments using physical and chemical processes removed little of the compounds (mean removal efficiency: 19%). Experimental sorption coefficients (Kd) of each studied compounds were also calculated. Sorption of venlafaxine, desmethylvenlafaxine, and carbamazepine on sludge was assumed to be negligible (log Kd ≤ 2), but higher sorption behavior can be expected for sertraline (log Kd ≥ 4). Ozonation treatment with O3 (5 mg/L) led to a satisfactory mean removal efficiency of 88% of the compounds. Screening of the final ozone-treated effluent samples by high resolution-mass spectrometry (LC-QqToFMS) did confirm the presence of related N-oxide by-products.


Effluent ozonation led to higher mean removal efficiencies than current primary treatment, and therefore represented a promising strategy for the elimination of antidepressants in urban wastewaters. However, the use of O3 produced by-products with unknown toxicity.

Antidepressants; Ozone; LC-MS/MS; Sewage treatment plants; Biosolids; Side-products

Graphical abstract