Desalination is the removal of salt from water, for example the desalination of sea water to produce fresh supplies. Reverse osmosis and thermal distillation now sustain beverage plants, food factories and irrigation in arid regions where freshwater runs scarce. Energy cost is the main drawback, and the concentrated brine left behind must be disposed of without harming marine ecosystems. Water destined for food use still needs mineral adjustment and disinfection to meet drinking-water standards, so desalination is only the first step.