A system for the treatment of water, the system comprising at least: a first water tank and a second water tank, where the first and second water tanks are connected to at least one water chamber, and where the system is configured such that water flows from the first water tank to the second water tank in a desalination mode and water flows from the second water tank to the first water tank in a salination mode; and an electrochemical desalination battery, EDB, unit, the EDB unit comprising: the at least one water chamber configured to hold water to be treated; at least one negative-ion redox electrode (1110, 1120) comprising a solution of an electrolyte material selected from cerium chloride, germanium chloride, vanadium chloride, europium chloride, and ferrous chloride, and capable of accepting, and having a reversible redox reaction with, at least one negative ion in the water; at least one positive-ion redox electrode (1160, 1170) capable of accepting, and having a reversible redox reaction with, at least one positive ion in the water, wherein the positive-ion redox electrode is immersed in the water chamber or separated from the water chamber by an optional porous separator; and an ion exchange membrane separating the at least one negative-ion redox electrode from the water chamber, wherein the EDB unit is configured to operate alternately in the desalination mode and in the salination mode; ions are released from the at least one negative-ion redox electrode (1110, 1120) and the at least one positive-ion redox electrode (1160, 1170), and energy is stored in the EDB unit in the salination mode; and the EDB unit desalinates water therein while releasing stored energy as output power employing the at least one negative-ion redox electrode (1110, 1120) as a positive output electrode and the at least one positive-ion redox electrode (1160, 1170) as a negative output electrode in the desalination mode, characterised in that the at least one negative-ion redox electrode (1110, 1120) and the at least one positive-ion redox electrode (1160, 1170) are arranged in the EDB unit such that a separation distance between the at least one negative-ion redox electrode (1110, 1120) and the at least one positive-ion redox electrode (1160, 1170) decreases along the direction of water flow during the desalination mode. a first water tank and a second water tank, where the first and second water tanks are connected to at least one water chamber, and where the system is configured such that water flows from the first water tank to the second water tank in a desalination mode and water flows from the second water tank to the first water tank in a salination mode; and an electrochemical desalination battery, EDB, unit, the EDB unit comprising: the at least one water chamber configured to hold water to be treated; at least one negative-ion redox electrode (1110, 1120) comprising a solution of an electrolyte material selected from cerium chloride, germanium chloride, vanadium chloride, europium chloride, and ferrous chloride, and capable of accepting, and having a reversible redox reaction with, at least one negative ion in the water; at least one positive-ion redox electrode (1160, 1170) capable of accepting, and having a reversible redox reaction with, at least one positive ion in the water, wherein the positive-ion redox electrode is immersed in the water chamber or separated from the water chamber by an optional porous separator; and an ion exchange membrane separating the at least one negative-ion redox electrode from the water chamber, the at least one water chamber configured to hold water to be treated; at least one negative-ion redox electrode (1110, 1120) comprising a solution of an electrolyte material selected from cerium chloride, germanium chloride, vanadium chloride, europium chloride, and ferrous chloride, and capable of accepting, and having a reversible redox reaction with, at least one negative ion in the water; at least one positive-ion redox electrode (1160, 1170) capable of accepting, and having a reversible redox reaction with, at least one positive ion in the water, wherein the positive-ion redox electrode is immersed in the water chamber or separated from the water chamber by an optional porous separator; and an ion exchange membrane separating the at least one negative-ion redox electrode from the water chamber, wherein the EDB unit is configured to operate alternately in the desalination mode and in the salination mode; ions are released from the at least one negative-ion redox electrode (1110, 1120) and the at least one positive-ion redox electrode (1160, 1170), and energy is stored in the EDB unit in the salination mode; and the EDB unit desalinates water therein while releasing stored energy as output power employing the at least one negative-ion redox electrode (1110, 1120) as a positive output electrode and the at least one positive-ion redox electrode (1160, 1170) as a negative output electrode in the desalination mode, characterised in that the at least one negative-ion redox electrode (1110, 1120) and the at least one positive-ion redox electrode (1160, 1170) are arranged in the EDB unit such that a separation distance between the at least one negative-ion redox electrode (1110, 1120) and the at least one positive-ion redox electrode (1160, 1170) decreases along the direction of water flow during the desalination mode.