Comparative analysis of desalination technologies: Energy, environmental impact, and freeze desalination potential for zero liquid discharge systems

The increasing volume of high-salinity brines generated by desalination challenges conventional single-process treatment. This study presents a comparative review of nine desalination technologies, with emphasis on freeze desalination (FD) as a complementary stage in hybrid zero liquid discharge (ZLD) systems. Technologies are assessed by specific energy consumption, water recovery rate, levelized cost of water, carbon footprint, water footprint, and ZLD compatibility. To address a literature gap, FD carbon and water footprints are estimated using a unified screening-level life-cycle assessment framework. Reverse osmosis remains the most energy-efficient option for seawater desalination (1.8–6 kWh/m 3 ), but its performance deteriorates at elevated salinity. FD shows operational advantages for highly concentrated brines (>70 g/L) approaching eutectic conditions. Reported FD energy consumption ranges from ~11.3 kWh/m 3 for single-stage seawater FD to higher values for multi-stage configurations; LNG-assisted systems can reach 2.34 kWh/m 3 under waste-cold integration. The screening-level (lower-bound) carbon footprint is 4.5–23.7 kg CO 2 -eq./m 3 (grid) and 0.6–5.2 kg CO 2 -eq./m 3 (renewables); the energy-driven water footprint is 0.023–0.118 m 3 /m 3 . FD is best positioned as a candidate stage for high-salinity brine treatment in hybrid ZLD systems. Because reported FD data remain limited to pilot-scale systems (≤30 m 3 /day; TRL 4–5), its systemic role remains a working hypothesis requiring industrial-scale validation.