## 2 Methods of Eliminating Hormones and Pharmaceuticals
### Combined Processes  
In recent years, the development of wastewater treatment technologies has focused on combining different physical, chemical, and biological methods to increase the removal efficiency of micropollutants, including hormones (e.g., E2, EE2, and E1) and pharmaceuticals. Table 9 shows the different configurations of the combined processes along with their mechanisms of action, removal efficiencies, benefits, limitations, and potential by-products. The highest removal efficiencies of both hormones (up to 99%) and pharmaceuticals (up to 98%) are shown by advanced combinations such as reverse osmosis (RO) with AOPs. Combinations of nanofiltration (NF) with ozonation or UV, as well as MBR (biological membrane reactor) with adsorption or AOP, also show efficiencies above 90%. Processes such as photocatalysts (TiO\({}_{2}\) with UV-C) or ultrasound combined with AOP provide good removal efficiencies but have the disadvantages of high energy costs and the need for catalysts. In contrast, methods based on coagulation and membrane filtration (UF/MF) show much lower efficiency in the elimination of micropollutants but are cheap and can protect further purification steps [31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90; 91; 92; 93; 94; 95; 96; 97; 98; 99; 100; 101; 102; 103; 104; 105; 106; 107; 108; 109; 110; 111; 111; 112; 113; 114; 115; 116; 117; 118; 119; 120; 121; 122; 123; 124; 125; 126; 127; 128; 129; 130; 131; 132; 133; 134; 135; 136; 137; 138; 139; 140; 141]. As far as by-products are concerned, the most \begin{table}
\begin{tabular}{c c c c} \hline \hline \begin{tabular}{c} **Name of** \\ **Compound** \\ \end{tabular} & \
\begin{tabular}{c} **Initial** \\ **Concentration** \\ **(mg/L)** \\ \end{tabular} & **Reactions** & **Time (min)** &
\begin{tabular}{c} **Degree of** \\ **Reduction [\%]** \\ \end{tabular} \\ \hline \multirow{3}{*}{EE2} & \multirow{3}{*}{1} & pH = 3; Fenton reaction, Fe\({}^{2+}\) = 28 mg/L & 10 & 50 \\ \cline{3-4}  & & Fe\({}^{2+}\):H\({}_{2}\)O\({}_{2}\) = 1:10 & 70 \\ \cline{3-4}  & & 30 & 90 \\ \cline{3-4}  & & 25 & 100 \\ \cline{3-4}  & & 30 & 100 \\ \cline{3-4}  & & 40 & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Degree of hormone removal in electro-Fenton process; authors’ own elaboration based on [132]. undesirable effects occur when using oxidation processes (ozonation and AOP), which can lead to the formation of aldehydes, ketones, carboxylic acids, brominated compounds, and trihalomethanes. It is therefore important to select combinations of technologies to ensure both high purification efficiency and the minimisation of harmful by-products. The advantages of many combination methods are their ability to remove difficult-to-degrade contaminants and the stability of operation under varying wastewater loads. Disadvantages tend to be operational costs, plant complexity, and the need for the regeneration of materials (e.g., activated carbon and MOF). Photocatalysis, as an advanced oxidation process (AOP), plays a key role in modern technologies for the treatment of the aquatic environment, especially in the context of the removal of organic micropollutants such as pharmaceuticals, plant protection products, or endocrinically active compounds. However, under real-world conditions, the effectiveness of conventional photocatalytic systems can sometimes be limited due to the short life of electron-hole pairs, the low availability of UV/vis light in the environment, and problems with the separation and recovery of the photocatalyst. In response to these challenges, integrated, multifunctional hybrid systems that combine photocatalysis with other physicochemical processes to increase purification efficiency and improve the operational properties of reaction systems have been developed in recent years [142; 143].