The availability of clean water is one of the key technological and social challenges of the 21st century. Currently, a variety of technologies are used for desalination, e.g., reverse osmosis (RO), electrodialysis (ED), and capacitive deionization (CDI). Electrically driven technologies such as ED and CDI have gained considerable attention in the last years for their potential ability to selectively remove ions from different water streams. However, the scale of the separation that is achieved with these technologies is still modest and limited to certain ionic species, mostly multivalent/monovalent separation. This thesis aimed to study the selective separation of monovalent ions, such as nitrate and chloride, using ED and CDI. The research included a comprehensive study of the variables that affect ion selectivity in these technologies, e.g., applied electric potential and ion concentration, from an experimental and theoretical point of view.