## 1 Introduction
This can lead to the development of antibiotic-resistant genes in natural water bodies and an increase in the occurrence of infections [13]. In article [14], a group of fourteen high-risk drugs was observed in hospital wastewaters, all of which have a hazard ratio greater than 10; TMP is included among them. Because of its frequent use and the fact that it is not effectively eliminated in wastewater treatment plants, TMP is frequently detected in wastewater effluents and surface waters. This highlights the need to remove it from the wastewater prior to its release into the environment. Several methods have been suggested for the degradation of trimethoprim, which include advanced oxidation processes (AOPs) like ozonation [15; 16; 17; 18; 19], membrane processes such as nanofiltration and reverse osmosis [20; 21], sonochemical processes [22], combined treatments [23], and adsorption processes [24; 25]. Over the past few decades, nanotechnology has rapidly emerged as a growing knowledge-based economy sector, primarily due to the unique physicochemical properties of nanomaterials. This technology has been widely encouraged because it has the potential to transform particles of metal, metal oxides, and other materials, often hybrid, into a new nano-form, which is smaller than 100 nm. Various types of nanomaterials, including magnetic nanoparticles, semiconductors, double hydroxide layers, ion exchange resins, alumosilicates, and graphene-based nanocomposites, have been utilized in water treatment technologies [26; 27; 28; 29; 30]. Out of the aforementioned nanomaterials, the authors opted to utilize a photocatalytic material in the form of a nanostructured TiO\({}_{2}\) film, adhered to a glass substrate. The use of such photocatalytic material to degrade organic micropollutants in water is classified as an AOP. TiO\({}_{2}\) has been the catalyst most used in research exploring the photocatalytic degradation of pharmaceuticals [31; 32; 33; 34]. In many photocatalytic studies, TiO\({}_{2}\) has been used in a suspended form for degrading organic pollutants. However, the immobilization of TiO\({}_{2}\) onto a substrate has been shown to result in lower efficiency due to a reduced number of active sites for generating oxidizing \({}^{\bullet}\)OH radicals or oxidizing positive holes (\(h^{+}\)), compared to suspended TiO\({}_{2}\) catalysts [35; 36]. However, the high cost and time required for the catalyst recovery and separation in the slurry system render it impractical for use in real-world applications. To address this, the authors concluded that a fixed bed approach, utilizing deposited photocatalytic films, would be more practical [37; 38; 39]. The authors of this study examined the degradation of TMP through photocatalysis using a specialized nanostructured film placed on borosilicate glass with a distinct shape and located at the base of a reactor that is exposed to radiation. During the nanostructured film preparation, the same procedure, as in [40], was followed, including the addition of PEG (polyethylene glycol, \(M_{\rm r}\) = 5000-7000, as an organic/polymer additive for increasing the surface roughness and, therewith, increasing the photocatalytic activity of the film) and calcination at 550 \({}^{\circ}\)C, which results in the formation of the photocatalytic film that consists only of anatase TiO\({}_{2}\) and shows granular microstructures with almost monodispersed spherical particles. The film was characterized by the following methods: XRD, AFM, FTIR, and Micro-Raman spectroscopy; and their results are also shown in references [39; 40]. The lamp used in the experiments was a sun simulator lamp, and the authors aimed to determine the reliability of using cheap natural solar radiation as the only source of energy required for the complete degradation of pharmaceuticals, such as TMP, in wastewater streams before their release into the environment.