[1] An electric current migrates dissolved salt ions, including fluorides, nitrates and sulfates, through an electrodialysis stack consisting of alternating layers of cationic and anionic ion exchange membranes.
[2][1] Current reversal reduces clogging of membranes, as salt deposits in the membrane gets dissolved when the current flow is reversed.
Electrodialysis reversal causes a small decrease in the diluted feed quality and requires increased complexity infrastructures, as reversible valves are required to change the flow direction of diluted and concentrated streams.
[3] The polarity reversal of EDR alternately exposed membrane surfaces and the water flow paths to concentrate with a tendency to precipitate scale and desalted water that tends to dissolve scale.
This allows the process to operate with supersaturated concentrate streams up to specific limits without chemical additions to prevent scale formation.