Potable water as well as water for agriculture and industry is critical to human habitation on this planet. We have been squandering and polluting this precious resource and are now in need of finding cost competitive newer technologies for reclaiming this valuable life-sustaining liquid. Capacitive deionization (CDI) is an electrochemical water treatment process that holds the promise of not only being a commercially viable alternative for treating water but for saving energy as well. CDI works by sequestering ions, or other charged species, in the electrical double layer of ultracapacitors. While removing these ions, one actually stores capacitive energy. If one recovers this energy efficiently, this process likely consumes less power than any competing technology. This paper reviews current methods for treating water in comparison to the state of art of the CDC process. (C) 2010 Elsevier Ltd. All rights reserved.