Recent development in high-salinity wastewater treatment technologies for zero liquid discharge

High-salinity wastewater, characterized by high osmotic pressure and complex composition, poses a major environmental challenge, making safe and resource-efficient treatment urgent. This review, framed within the full zero-liquid-discharge (ZLD) process, systematically examines mainstream and emerging technologies across "pre-treatment-core treatment-post-treatment." For core treatment, reverse osmosis (RO) is the most mature, with derivative processes like high-pressure reverse osmosis (HPRO) and Osmotically Assisted Reverse Osmosis (OARO) extending the applicable salinity up to 120 g/kg and controlling specific energy consumption at 3-22 kWh/m³, and future advances require membranes with higher pressure tolerance, fouling resistance, and chlorine stability. Conventional thermal concentration covers the full range from high-concentration brine to saturated crystallization, with energy use of 40-250 kWh/m³, and benefits from high-performance corrosion-resistant alloys and protective coatings. Emerging methods such as humidification-dehumidification and solar distillation theoretically handle full-salinity streams but still face low-efficiency limitations. The review also highlights hybrid processes (membrane-thermal, thermal-thermal), the role of pretreatment like chemical softening and nanofiltration in reducing scaling, and the potential of novel drying and intelligent control technologies in post-treatment. Overall, high-salinity wastewater management should move beyond single-path optimization toward an integrated "materials-energy-process" low-carbon strategy.