## 1 Introduction  
The issue of water scarcity and how it can be solved continues to be a challenge to the world [1]. Herein, the continuous acceleration of water pollution due to population growth, urbanization, and industrialization, and the corresponding demand for non-renewable sources, has greatly increased [2]. Currently, South Africa's municipalities are failing to provide clean water due to inadequate wastewater treatment facilities and limited or exhausted water resources. Piped water in two-thirds of South Africa's municipalities do not meet minimum potable water standards [3, 4, 5]. The wastewater contains several contaminants, such as organic pollutants (dyes, phenolic compounds, surfactants, etc. ), pathogenic microorganisms, and a range of different colloidal particles, which have harmful impacts on humans, animals, and the environment [6, 7, 8]. Their removal is therefore paramount. Several conventional wastewater treatment methods have been employed for decades. However, over the years, new and more challenging contaminants have emerged, and these contaminants have proven to be difficult to remove by traditional methods. Biological treatment methods commonly used are activated sludge and biofilm processes. However, high investment and operating costs, susceptibility to sludge swelling, and long pre-preparation cycles are the issues that exist in biological treatment processes [9]. Therefore, alternative and more advanced techniques are required [6; 10]. Advanced oxidation processes (AOPs), an emerging wastewater treatment technology, displays great potential for the degradation of a variety of organic contaminants [2]. This process involves the generation of a highly reactive hydroxyl radical, which destroys the contaminants. Photocatalytic oxidation is a type of AOP whereby the photo-activated reactions are distinguished by the free radical mechanism initiated by the interaction of photons of an appropriate energy level with the catalyst [11]. Several researchers have investigated the use of photocatalysis for targeting individual pollutants. Most antibiotics are metabolized partially in the body, but 30% to 90% of them are discharged into the municipal sewage system without being metabolized [12; 13]. [PERSON] et al. [14] reported on the application of a photocatalytic process using nanoparticles for TiO\({}_{2}\) on the removal of COD and metronidazoleazole. The results on real wastewater (containing metronidazoleazole at 80 mg/L and COD equal to 900 mg/L) showed that metronidazoleazole and COD removal efficiencies at optimal conditions were 58.32% and 34.32%, respectively. [PERSON] et al. [15] found that an increase in catalyst load increased the decolourization and degradation percentages in their work to degrade methylene blue dye. However, the catalyst load may not exceed a certain quantity; otherwise, the degradation and decolourization percentages start to decrease due to light scattering and screening effects. This causes the catalyst's surface to become unavailable for photon absorption. Furthermore, refs. [16; 17; 18; 19] reported that excessive catalyst loading results in turbidity and a blocking effect that reduces light transmission through the whole solution and causes light scattering and a screening effect that decreases the degradation and decolourization percentages. The effect of light intensity is vital in the photocatalytic process, as the presence of sufficient light energy and wavelength allows for photocatalyst activation and enhances the generation of the hydroxyl and oxide radicals. In addition, refs. [16; 17; 20] stated that to achieve a high photocatalytic rate, specifically in water treatment, a reasonably high light intensity is required to sufficiently provide each TiO\({}_{2}\) active site with enough photon energy.