Desalination is the process of removing dissolved salts and minerals from seawater or brackish water to produce freshwater. Reverse osmosis and thermal distillation are the two primary technologies used.
Desalination is the engineered process of separating dissolved salts and other minerals from saline water (seawater or brackish groundwater) to produce freshwater suitable for drinking, irrigation, or industrial use. The two major categories of desalination technology are membrane-based processes, primarily reverse osmosis (RO), and thermal processes, including multi-stage flash distillation (MSF) and multi-effect distillation (MED). Reverse osmosis forces saline water through semi-permeable membranes under high pressure, rejecting dissolved salts, and accounts for approximately 65 percent of global desalination capacity. Modern RO plants can achieve energy consumption of 3-4 kilowatt-hours per cubic meter, a significant improvement from earlier technologies. Global desalination capacity exceeds 100 million cubic meters per day, with the largest plants in the Middle East, where desalination provides the majority of freshwater supply. The primary challenges of desalination include high energy requirements (making it the most expensive conventional water supply source), disposal of concentrated brine that can harm marine ecosystems, chemical use for membrane cleaning and pretreatment, and the carbon footprint associated with energy consumption. However, declining costs, integration with renewable energy sources, and growing water scarcity are driving expansion of desalination worldwide. Brackish water desalination requires significantly less energy than seawater desalination due to lower salt concentrations.