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When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
The continuous discharge of emerging contaminants (ECs) to the aquatic ecosystem generate concerns due to their unpredictable risks to human and environment. Particularly, when wastewater treatment facilities do not eliminate adequately ECs due to currently used technologies.
The aim of this research was to enhance the wastewater treatment to the level of its potential reuse as a source of water. The investigations were conducted at lab and pilot scale in 8 phases and a number of stages. Initially, the removal of selected ECs was optimized. Subsequently, the by-product formation and their identification were conducted. Then, the study focused on the by-product removal. In subsequent phases, the optimal technological parameters were verified in natural conditions, at the pilot scale in AOP (advance oxidation process) and AO-MEBR (membrane electro-bioreactor) facilities. Such approach permitted to study the removal of sulfamethoxazole (SMX), 17- alpha ethynyl estradiol (EE2), caffeine (CAF) and paracetamol (PCM) from various aqueous solutions. A developed model investigated the effect of technological parameters on pharmaceuticals’ removal efficiency and on abatement of by-products.
The results showed superior removal efficiency (99%) by both UV/H2O2 AOP and UV/O3 AOP of SMX, PCM, CAF and EE2 in comparison to sole UVC photolysis (30-40%). Ozone based UV/O3 AOP demonstrated an elevated rate and removal (10-15 % more) in comparison to ozonation alone. The target ECs such as SMX, PCM were removed more than 80% in effluent and more than 90% in river water during 60 minutes.
Four major SMX by-products, identified by LC-MS-MS, revealed longer life time and stability even after parent SMX ion removal. By applying optimal technological parameters, i.e. pH, oxidant dose and aeration rate, the by-products amounts were successfully controlled. Furthermore, the toxicity was decreased and energy consumption for target pollutant removal was minimized.
The AO/MEBR system not merely improved the quality of effluent with respect to refractory organic pollutants, but also likely promoted by-products and toxicity mitigation as well as saving energy leading to improved potential of water recovery from sewage.