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Abstract

This thesis focuses on the fate of chosen antidepressants in the environment. Studied compounds belong to the class of selective serotonin reuptake inhibitors. Reportedly they do not completely mineralize by existing water treatment processes and their residues cause unwanted toxic effects in aquatic organisms. However, to date, insufficient information has been gathered to form an action plan for managing their presence in the environment, and especially detailed information on processes they undergo during wastewater treatment and after they enter the environment is missing.
A literature overview revealed that among the commonly used treatment techniques, secondary biological treatment with activated sludge is the most efficient in removing selective serotonin reuptake inhibitors, with some compounds, like sertraline being rarely addressed. Accordingly, the processes involved in its removal and the efficiency of the sludge-based treatment were studied. The results revealed adsorption to sludge as the primary removal process, followed by biodegradation. Removal efficiencies fluctuated between 77% and 81% in conventional wastewater treatment plants with activated sludge and exceeded 90% in laboratory-scale simulations. Structures of ten transformation products were identified and their presence was detected in actual wastewater samples.
Sertraline and paroxetine were chosen for the degradation study during exposure to sunlight in surface waters. Their photochemistry was researched, and the data was modelled to obtain information on their degradation kinetics. Altogether fourteen transformation products were identified, and degradation pathways were proposed. Both compounds were readily photodegradable with half-lives of only a few days in shallower water. In both cases, direct photolysis and reactions with photochemically produced reactive intermediates, more specifically hydroxyl and carbonate radicals, were the main degradation pathways. The presence of three sertraline transformation products was confirmed in surface waters for the first time.
For all the studies mentioned above to be successful, sensitive, robust, and precise analytical methods were developed. Also, specialized materials, i.e., imprinted polymers with sertraline as the template, were developed to improve the sample preparation step by increasing recovery and minimizing matrix effects. Some difficulties were, however, encountered when using them for trace-level analysis. Then again, they were well suited as alternative wastewater treatment sorbents for removing selective serotonin reuptake inhibitors. The materials were also cross-reactive for metabolites and transformation products of selective serotonin reuptake inhibitors.
Altogether, this thesis fills the knowledge gap regarding the behavior of selective serotonin reuptake inhibitors after they leave the human body and is a sound basis for further research. For example, the newly identified transformation products should lead to a more thorough study of the environmental impact of the studied antidepressants. Further, insight is provided into an alternative water purification technique applying molecularly imprinted polymers. Lastly, the experimental designs used in our studies can be applied to other environmental contaminants.