Ion-Exchange and Water Softening

Ion-exchange and water softening is used to soften hard water, which is typically due to high amounts of magnesium and calcium salts. During the treatment process, ions, cations and anions in water are exchanged with anions and cations from ion-exchange media. Water softeners are used for example in power and heat and steam plants, laundries and other processes where hard water creates problems (limescale formation/scaling). To remove ionic dissolved salts and minerals completely, a mixed bed media can be used.

Water softeners are typically regenerated using normal salt (sodium chloride is added periodically to the brine tank).

Ion-exchange system equipment

An ion-exchange and water softening system typically consists of pressure/filtration vessel(s) filler with media, valves and piping and a brine tank. An additional pump is usually not needed as the filters are typically operated using the supply network pressure. The applied media is usually polymer resin. Depending on the capacity/flow of the system, the valve and control system can be based on either standard automatic water filtration valves (e.g. Autotrol, Fleck or Clack, etc.), water filtration valves + an external control system or loose valves + an external control system.

Ion-exchange filters/water softeners require regular regeneration to maintain their performance. During regeneration, the media’s capacity to capture ions is restored by injecting saturated salt (sodium chloride) brine into the media and back-flushing the filter into a drain. If the need for treated water is continuous (including during the regeneration cycle), the system is equipped with two or more filtration vessels (only one vessel is in regeneration at a time, while the others are in normal operation).

Required information for ion-exchange and water softening system design

To complete a water treatment system design, a raw water analysis is needed together with information about the required water flow/capacity of the system and the required water quality after treatment or information about the use of the water produced. If the equipment is being installed in an existing space, information about the available drainage and room dimensions is also good to know.