The present disclosure is directed at an apparatus, method and plant for desalinating saltwater and contaminated saltwater. The apparatus comprises a stack and a manifolding assembly. The stack comprises a product chamber, a first and second concentrate chamber, an anion exchange membrane forming a boundary between the first concentrate chamber and the product chamber and a cation exchange membrane forming a boundary between the second concentrate chamber and the product chamber. The manifolding assembly comprises product and concentrate manifolding fluidly coupled to the product and concentrate chambers respectively, to convey a saltwater being desalinated to and away from the product chamber, and a concentrate to and away from the concentrate chambers. The stack may include a diluent chamber and adjacent anion or cation exchange membranes between the product chamber, diluent chamber and concentrate chamber to respectively convey anions or cations across multiple chambers. The stack may also contain a rinse chamber bounded by an anion exchange membrane to guard the stack electrodes from scaling cations. A cleaning system for cleaning the stack is also disclosed.