Water purification system and method

A water purification system and method for producing high-purity, laboratory-quality product water from feed water containing a concentration of dissolved ions and other contaminants. The water purification system includes a reverse osmosis unit and a capacitive deionization module positioned in a recirculation path coupling a concentrate outlet of the reverse osmosis unit in fluid communication with a feed water inlet of the reverse osmosis unit. The capacitive deionization unit removes dissolved ions from the concentrate stream, which is admixed with feed water provided to the feed water inlet of the reverse osmosis unit. A permeate outlet of the reverse osmosis unit outputs a stream of the high-purity product water to be, for example, stored in a storage tank.