text: Electrodeionization was developed in the early 1950s to eliminate or minimize the concentration polarization phenomenon present in electrolysis systems of the time. A patent on the technology was filed in 1953, and subsequent publications popularized the technology.
  The technology was limited in application because of the low tolerance of total dissolved solids, hardness and organics. During the 1970s and 1980s, reverse osmosis became a preferred technology to ion exchange resin for high TDS waters. As RO gained popularity, EDI emerged as a suitable polishing technology. Packaged RO and EDI systems began to displace chemically regenerated ion exchange systems.
  In 1986 and 1989, several companies developed new EDI devices. The initial devices were large, costly, and often unreliable. However, in the 1990s, smaller and less costly modular designs were introduced. Nonetheless, these designs and their contemporary descendants still face limitations such as cost and limited operational envelope.