**3.1 Membrane technology**

Membrane technology (MT) encompasses the related engineering and scientific approaches for the transport of components, species, or substances through or by membranes [44]. This technique is generally adopted to explain the mechanical processes for the separation of gas or liquid streams. Membranes are classified as a thin layer barrier for size differential separation, which are usually integrated with chemical and biological treatments, or as a standalone system in secondary treatment of wastewater [44, 45]. For a typical membrane mechanism, there is usually a driving force such as a semi-permeable barrier which controls the rate of movement of components by fractional permeation, and rejection through pores of different sizes as depicted in **Figure 1**. The permeation and selective rejection are a function of the membrane pore size and chemical affinity, allows for a product stream devoid of target components. Some advantages and drawbacks are presented in **Figure 2**.

#### **Figure 1.** *Membrane selective permeation for various solutes adapted from Tetteh et al., 2019 [45].*
