## 2 Methods of Eliminating Hormones and Pharmaceuticals
### Physical Methods
#### 2.1.3 Nanofililtration  
Nanofiliration (NF) uses membranes with a pore size of approximately 0.001 um, which allows for the effective removal of organic compounds with a molecular weight of more than 200-300 Da, including many pharmaceuticals and hormones such as diclofenac, ibuprofen, and ethinylestradiol [68]. NF is dependent on the type of membrane, and a number of comparative studies can be found on this topic in the literature, e.g., studies on the relationship between the retention factor of bisphenol A and the type of nanofiltration membrane for a deionised water solution. The values for bisphenol A retention rates ranged from about 62% (for DK membrane) to approximately 94% (for the NF-90 and HL membranes) [68]. Differences in bisphenol A removal efficiency for the tested membranes were observed due to their different physicochemical properties. When the effect of membrane type and properties on the removal efficiency of the micropollutant under investigation is analysed, both its molar mass limit and hydrophobic properties should be taken into account. This is particularly important when comparing nanofiltration membranes from different manufacturers because despite having a similar membrane-forming polymer, membranes have different surface properties. This is due, among other things, to the addition of various admixtures to the polymer, which are not revealed by the membrane manufacturer. A parameter that represents the hydrophobic properties of a membrane is the wetting angle [74]. According to data from the literature, as the wetting angle increases, the hydrophobicity of the membrane surface increases. In the case of the NF-90 membrane, the authors of [68; 74] found a high retention of bisphenol A. The HL membrane showed similar separation properties towards bisphenol A. The NF-90 and HL membranes have similar transport properties, as evidenced by the permeate flux value [68; 74]. When assessing the effectiveness of a membrane filtration process for the elimination of micropollutants, it is also imperative to perform tests with solutions containing other organic and inorganic substances that are designed to initiate fouling and/or scaling of the membrane. Fouling and scaling phenomena accompany membrane filtration, contributing to a reduction in membrane performance. The authors of [75; 76; 77] carried out tests for a model effluent containing model organic and inorganic substances in addition to bisphenol A. During the filtration process, the flux of the permeate volume of the NF-90 membrane, characterised by a high wetting angle, decreased. The compact structure of nanofiltration membranes (including pore size) makes them highly susceptible to adverse phenomena that accompany membrane filtration that contribute to a decrease in membrane hydraulic performance [68; 75; 76; 77]. The NF-90 membrane showed the highest degree of elimination (Figure 2). Differences in micropollutant retention were observed due to their different physicochemical properties. The nanofiltration membrane has a similar hydraulic capacity to that of deionised water. The average flux of permeate volume for deionised water is approximately \(40\times 10^{-6}\) m\({}^{3}\) m\({}^{-2}\) s\({}^{-1}\), while for the actual outflow, this value decreased to \(4\times 10^{-6}\) m\({}^{3}\) m\({}^{-2}\) s\({}^{-1}\). The NF-90 membrane is not resistant to fouling caused by contaminants present in the actual outflow. It should be noted that the separation of micropollutants is affected by several membrane phenomena, including the reduction in the zeta potential and the presence of a filter cake on the membrane surface. Membrane fouling increases the intensity of the micropollutant adsorption phenomenon and limits the process of diffusion of compounds through the membrane [68; 69; 78]. Figure 3 shows the relationship between the pore size of HL and NF-90 membranes and the removal efficiency of E2, EE2, E1, and BPA from wastewater by nanofiltration.