*Pathways and Challenges for Efficient Desalination*

*Energy Recovery in Membrane Process DOI: http://dx.doi.org/10.5772/intechopen.101778*

**Figure 4.**

*Calculated specific energy consumption as a function of membrane water permeability for single-stage SWRO from several references at different conditions.*

#### **Figure 5.**

*Calculated SEC as a function of membrane permeability for BWRO from several references.*

**Figure 6.**

*Calculation of the required number of pressure vessels in order to investigation of function of the membrane water permeability for single-stage BWRO with12 bar feed pump pressure, 2000 ppm feed, 65% recovery rate and single stage SWRO with 42% recovery rate, 42,000 ppm feed and 70 bar feed pump pressure for total capacity of 100,000 m<sup>3</sup> /d.*

### **3. RO membrane: types, structures and materials**

Based on the membrane structure, The RO membrane is consisted of two groups: conventional thin-film composite and thin-film nanocomposite. Based on the thin-film material, conventional RO membrane is classified into two main

groups: cellulose acetate (CA) and aromatic polyamide (PA). The RO membrane on the basis of the membrane configuration can be divided into three main groups: hollow-fiber, flat-sheet (plate-and-frame) and spiral-wound [30, 31].
