###### Abstract  
Sulfonamides, including sulfadoxine (SDX), are widely used antibiotics, particularly for malaria treatment. However, their extensive use has led to environmental pollution, microbial resistance, and public health risks. Advanced Oxidation Processes (AOPs) offer promising methods to degrade such pollutants in water, though they may generate more toxic by-products. This study evaluates three AOPs with different hydroxyl radical generation principles: the Fenton reagent (H\({}_{2}\)O\({}_{2}\)/Fe\({}^{2+}\)), hydrogen peroxide photolysis (UV-C/H\({}_{2}\)O\({}_{2}\)), and heterogeneous photocatalysis (UV-A/TiOsynthase (DHPS), a key metabolic enzyme in folic acid biosynthesis. This molecule plays a crucial role in facilitating the metabolism and transport of carbon units and is involved in a specific metabolic pathway in which methyl groups are converted into triphosphates during DNA synthesis [4; 5]. Through this precise mechanism, SDX effectively stops an essential metabolic process of the pathogen and suppresses the spread of infection. The phenomenon of bacterial adaptation and the development of drug resistance is a well-documented and worrying aspect of modern medicine. Bacterial species have shown the ability to evolve and develop defence mechanisms in response to prolonged exposure to pharmaceutical agents, posing significant challenges to the efficacy of future antimicrobial therapies [6; 7; 8]. Bacteria have shown amazing abilities to rapidly adapt to such environments. One example of this is the species of Staphylococcus, which has developed resistance to paracetamol in a remarkably short time--only 18 years after its first use [9]. This alarming trend illustrates the extent of the threat posed by the widespread presence of PPs in the environment. Consequently, it is imperative to adopt comprehensive strategies aimed at mitigating the impact of pharmaceutical residues on the environment while addressing the challenges posed by antimicrobial resistance. The main pathways through which active pharmaceutical ingredients enter the environment include public and industrial sewage systems [10]. In response to the growing awareness of the environmental hazards posed by such residues, regulatory frameworks such as those in European legislation have been established to limit the release of these substances into aquatic ecosystems [6; 11; 12]. Conventional activated sludge treatment in wastewater treatment plants has been shown to be ineffective in removing a variety of PPs by biodegradation [13]. The need for tertiary technologies that effectively address the challenge of complete removal of PPs and other toxic organic micropollutants from wastewater to protect the aquatic environment and promote the potential reuse of treated effluents has led to the development of so-called Advanced Oxidation Processes (AOPs) [14; 15; 16; 17; 18]. AOPs involve the generation of highly reactive, non-selective hydroxyl radicals through the application of processes such as photolysis, ozonation, photocatalysis, or treatment with hydrogen peroxide. These hydroxyl radicals effectively oxidize and degrade a wide range of organic contaminants, including pharmaceuticals, leading to the generation of transformation products (TPs) [19; 20]. Traditionally, the presence of TPs was not a cause for concern, as their potential impact on the environment was either unknown or ignored. However, recent research studies have highlighted the importance of TPs as emerging contaminants [12; 21]. Unlike PPs, which have known and predictable pharmacological properties and environmental fate, TPs can have different chemical properties and toxicological profiles, posing new challenges for environmental risk assessment and management [22; 23; 24; 25]. While the degradation of PPs is a key objective in wastewater treatment, it is therefore crucial to consider the fate and impact of TPs generated in such processes and to aim for higher levels of mineralization.