Desalination Technology: Reverse Osmosis Thermodynamics, High-Recovery Configurations, and Sustainable Brine Management
Desalination technology provides a critical non-conventional water supply solution by extracting fresh potable water from seawater and brackish groundwater sources. Seawater Reverse Osmosis (SWRO) dominates modern desalination infrastructure, utilizing semi-permeable polymeric membranes to overcome high osmotic pressure gradients and separate dissolved inorganic salts from water molecules. The theoretical minimum thermodynamic work of separation ($W_{\text{min}}$) required to extract fresh water from seawater at recovery ratio $R_{\text{rec}} = \frac{V_p}{V_f}$ is evaluated using chemical potential principles: $$W_{\text{min}} = -\frac{R \cdot T}{V_p} \cdot \left[ n_w \cdot \ln(a_w) + n_s \cdot \ln(a_s) \right]$$ Where $R$ is the universal gas constant, $T$ is absolute temperature, $V_p$ is permeate volume, $n_w$ and $n_s$ are mole quantities of water and salt, and $a_w$ and $a_s$ represent their chemical activity coefficients. For standard seawater ($35,000\text{ mg/L}$ total d...