The current state of the art for water softening is ion exchange in columns packed with functionalized resin. The ion-exchange resins (IERs) work by adsorbing scale forming ions (calcium, magnesium) and replacing them with another ion, sodium, in the softened water. These resins must be periodically regenerated using large amounts of food grade salt, a consumable chemical that must be purchased.  Additionally, this water softening method introduces a high salt load into municipal sewer systems and water treatment plants.

An alternative process is to use water desalination technology, such as reverse osmosis (RO). Reverse osmosis uses membranes that allow only water to pass through membranes easily while restricting the passage of contaminants. However, a RO membrane is non-selective; the membrane is capable of removing all the ions present in the water, but not a targeted  contaminant. This characteristic reduces the possible efficiency of using RO to treat water for specific trace contaminants such as magnesium and calcium.

A promising method for water softening may be Capacitive DeIonization (CDI), which has the potential to be ion-selective as well as more energy efficient for low-salinity desalination compared to techniques such as RO. Unlike IER or RO methods, CDI removes ions with electric fields, taking advantage of the inherently charged ions, which would naturally be attracted to the charged porous electrodes and thus separating them from the feed water.