Electrodialysis (ED) is an electrically driven membrane process used to demineralize or desalinate brackish and saline water. Brackish waters lie under approximately two-thirds of the United States, and some inland rivers, such as portions of the Rio Grande and the Colorado, are also brackish. Water is generally classified as brackish when mineral content ranges between that of fresh drinking water and that of seawater; brackish water contains more than 500 mg/L of total dissolved solids (TDS), and seawater contains more than 30,000 mg/L TDS. ED systems are capable of treating variable source water quality while producing a consistent finished water quality. According to the Global Water Intelligence (GWI) DesalData website (incorporating the IDA Desalting Plants Inventory), the installed worldwide capacity of ED membrane treatment plants increased from 2 mgd (315 m3/h) in 1955 to more than 200 mgd (31,545 m3/h) in 1992 and more than 758 mgd (119,556 m3/h) in 2019. Need it now? Learn about AWWA's digital downloads.
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