Activated alumina, ion exchange and reverse osmosis are all effective devices for greatly reducing or completely removing arsenic levels from a water supply. The best method for arsenic filtration depends on the type of arsenic compound that is present in the water supply, the level of experience the operator has in using the unit, and the chemistry of the water being filtered.
Activated alumina works by passing water through an alumina filter that attracts arsenic atoms, and it is highly effective at filtering out both arsenic trioxide and arsenic (V) acid. A disadvantage to using the activated alumina method is that the filters must be treated with strong acid and base solutions periodically and the storage and handling of these solutions are is not recommended for non-professionals.
Ion exchange removes charged arsenic ions from a water supply and replaces them with chloride like a conventional water softener. Because ion exchange removes charged ions from water, it is highly effective at removing arsenic (V) acid, but it will not remove arsenic trioxide. Another disadvantage to ion exchange is that suspended particles and precipitated iron present in the water my clog the filter in the unit. The long-term use of ion exchange is also not recommended for non-professionals due the unit's maintenance needs.
When operating properly, reverse osmosis will remove more than 95 percent of any arsenic present in a water supply. It also does not require heavy maintenance that would need to be overseen by a professional. One disadvantage to using a reverse osmosis unit is the need to properly dispose of high-salinity waste water that the unit produces as a by-product of water filtration.