desalination

Desalination is the process of removing salts and other minerals from saline water to produce fresh water that is suitable for drinking, irrigation, or industrial use. It is most common for seawater but can also treat brackish groundwater or saline wastewater. Desalination facilities are increasingly deployed in arid coastal regions and island communities where natural freshwater resources are limited.

The main approaches fall into thermal and membrane technologies. Thermal methods, including multi-stage flash and multi-effect distillation, use heat to evaporate water and then condense the vapor to obtain desalinated water. Membrane processes primarily use reverse osmosis, which forces water through semi-permeable membranes to reject salts; nanofiltration and electrodialysis are also used, especially for brackish water. Pretreatment removes particulates and scale-forming minerals to protect equipment, and post-treatment adjusts mineral content, disinfection, and taste.

A typical plant sequence includes seawater or brackish water intake, pretreatment, desalination, post-treatment, and distribution. The concentrate or brine stream is discharged back to the source, often after dilution or treatment. Energy use is a critical consideration; reverse osmosis has become the dominant technology due to lower energy intensity and capital costs, though thermal plants persist where waste heat or high-temperature resources are available. Energy recovery devices and the use of renewable energy are increasingly pursued to reduce costs and emissions.

Environmental and economic aspects include brine management, intake effects on marine ecosystems, chemical use, and the high capital and operating costs. Desalination is generally more expensive than conventional freshwater sources, but its viability improves with scale, technological advances, and integration with renewable energy or co-located heat sources.