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'''Ion Exchange''' has long been used as a water-softening process, although usually on a single-home basis. Traditional anion exchange is effective in removing As(V), but not As (III), or arsenic trioxide, which doesn't have a net charge. Effective long-term ion exchange removal of arsenic requires a trained operator to maintain the column.
Both '''Reverse osmosis''' and '''electrodialysis''' (also called ''electrodialysis reversal'') can remove arsenic with a net ionic charge. (Note that arsenic oxide, As<sub>2</sub>O<sub>3</sub>, is a common form of arsenic in groundwater that is soluble, but has no net charge.) Some utilities presently use one of these methods to reduce [[total dissolved solids]] and therefore improve taste. A problem with both methods is the production of high-salinity waste water, called brine, or concentrate, which then must be disposed of.
'''Subterranean Arsenic Removal (SAR) Technology''' [http://www.insituarsenic.org SAR Technology]
