## 2 Methods of Eliminating Hormones and Pharmaceuticals
### Physical Methods
#### 2.1.6. Ultrasound  
The ultrasonic process is a promising approach to eliminating organic micropollutants, including steroid hormones and pharmaceuticals, from wastewater. The mechanism of action is based on the phenomenon of acoustic cavitation in which high-frequency ultrasonic waves (20-60 kHz) generate microbubbles of gas in a liquid. These bubbles undergo cyclic growth and violent implosion, causing a local increase in temperature (up to approx. 5000 K) and pressure (up to 500 atm), which results in the homolytic breakdown of molecules and the formation of reactive oxygen species (ROS), including hydroxyl radicals [94; 95]. Compounds such as 17\(\alpha\)-ethynylestradiol (EE2), estrone (E1), and oestradiol (E2) are highly susceptible to radical oxidation reactions due to the presence of reactive phenolic groups. This was confirmed in [PERSON]'s studies [96] in which the addition of butyl alcohol, an inhibitor of hydroxyl radicals, reduced the efficiency of oestrogen removal from the range of 56.3-79.2% to 30.8%, clearly indicating the dominant mechanism of radical oxidation. Figure 5 illustrates the effectiveness of the sonodegradation of selected hormones and pharmaceuticals. The highest removal levels were recorded for EE2 (92%), E2 (88%), and E1 (85%), confirming their high reactivity to ROS. In the case of the following pharmaceuticals, removal was lower: paracetamol (82%), ibuprofen (75%), diclofenac (68%), and carbamazepine (55%). The lower removal efficiency of carbamazepine is attributed to its stable molecular structure and low chemical reactivity. The efficiency of the process depends on many operating parameters, including the frequency and power of the ultrasound, exposure time, pH, and salinity and alkalinity of the environment [97; 98; 99; 100]. The greatest influence is attributed to the frequency and power of ultrasound (approx. 23%), while exposure time was the least important parameter (6.5%) [99]. An increase in frequency and power intensity leads to intensified cavitation, which increases ROS generation and degradation efficiency [100]. For example, an efficiency of 94% was achieved with 120 min of exposure, a frequency of 60 kHz, a power  
Figure 4: The effectiveness of removing selected hormonal compounds and pharmaceuticals from wastewater using reverse osmosis; the authors’ own elaboration based on [80; 81; 82; 87; 88; 89; 90; 80; 82]. of 110 W, and a pH of 7-10. The effect of pH on the course of the reaction is complex and depends on the type of compound. According to research [101], the degradation of oestrogens was more effective in an alkaline environment (pH 10), where 95% removal was achieved after 10 min. In contrast, [PERSON] [96] pointed to higher efficiency in an acidic or neutral environment, and other studies [95] suggest that lowering the pH from 7.8 to 3 may limit the breakdown of EE2, indicating the need for individual optimisation of parameters. Environmental parameters such as salinity and alkalinity also affect the efficiency of the process. The presence of sodium chloride (0.17 M NaCl) and sodium bicarbonate (120 mM NaHCO\({}_{3}\)) increases removal efficiency, mainly by improving conductivity and cavitation conditions [100]. Salinity had a stronger effect than alkalinity, and their combined effect led to a synergistic effect. The advantages of the process include low energy consumption, no formation of toxic by-products, and the possibility of selective degradation of specific compounds [101]. Under laboratory conditions, both immersible systems (ultrasonic probes) and ultrasonic baths are used to control key parameters. Typical conditions are a frequency range of 20-60 kHz, a power range of 60-110 W, an exposure time of 10-120 min, a temperature range of 20-25 \({}^{\circ}\)C, and a pH range of 3-10 [94; 95; 96; 97; 98; 99; 100]. Analytical techniques such as HPLC-MS/MS, UV-Vis spectrophotometry, and TOC analysis are used to evaluate effectiveness [95; 96; 97].