UVC induced photo-removal of sulfamethoxazole (SMX), levofloxacin (LEVO), 17-alpha-ethinylestradiol (EE2) and levonorgestrel (LNG) in wastewater

The potential development of antibacterial resistance and endocrine disruption has lead to increased research investigating the removal of antibiotics and synthetic (or natural) hormones from water by various methods. Biodegradability of these compounds was generally reported to be low and these pharmaceuticals were frequently detected in sewage and wastewater treatment plant (WWTP) effluents. Therefore, alternative or complementary removal techniques to conventional wastewater treatment are necessary in order to mitigate potential health hazards associated to these contaminants. Investigation of advanced oxidation processes (AOPs) for removal of variety of pharmaceutically active compounds has received great interest in the recent years. In the Ph.D. thesis presented here, results associated to photocatalytic removals under UVC radiation of two antibiotics: sulfamethoxazole (SMX) and levofloxacin (LEVO) and two synthetic hormones: 17-α-ethinylestradiol (EE2) and levonorgestrel (LNG) are presented. UVC radiation is chosen since it is commonly used in water sterilization facilities. It was shown that photolysis is the dominant mode of removal of SMX during photocatalysis under UVC radiation. Even though, photolytic removal of this compound was faster, higher mineralization efficiency was reported for photocatalysis. Both UVC mediated treatments lead to the generation of products which are more toxic than the parent compound as determined by Daphnia magna toxicity tests. There are currently no data on the photocatalytic removal of LEVO under UVC radiation, and this Ph.D. thesis provides the first set of data in literature about its photocatalytic removal. The results showed that the direct photolytic removal of this compound is not significant, and during photocatalysis more than 97% of LEVO is removed after 120 minutes of irradiation. The effectiveness of photocatalysis is shown by comparing these results to its removal by ozonation (another AOP). Ozonation leads to the generation of persistent products which are removed subsequently by photocatalysis. The generated products of photocatalytic treatment of LEVO were shown to contain no residual antibacterial activity. The applicability of this type of treatment to waters containing LEVO was verified. Concerns for increased antibacterial resistance of pathogens in receiving waters can be mitigated by employing this treatment. EE2 and LNG are commonly used in combination in oral contraceptive pills. EE2 is a synthetic estrogen commonly detected and was shown to have adverse endocrine disrupting effects at environmentally relevant concentrations. LNG is a synthetic progestin, research on its occurrence and potential health effects just started to be explored in the recent years. This Ph.D. thesis provides for the first time in literature, the photolytic and photocatalytic removal of LNG as an individual contaminant as well as in mixtures of EE2 and in a real pharmaceutical wastewater. Photo-removal experiments showed that LNG is significantly more sensitive to UVC…