Ion Exchange Denitrification
Denitrifyers are Ion Exchange equipments that use anionic resins to replace with chloride all those anions that present more affinity with the resin that chloride. This alternative is highly recommendable for waters with low salinity and high content of nitrate, when demineralizing is not necessary and nitrate removal (or reduction) is.
Resins are small polymeric spheres about 0.5 mm diameter, on whose surface the anion exchange reaction occurs (sulphates and nitrates are exchanged for chloride).
Once the resin is saturated by the adsorption of anions, it is necessary to regenerate it, and this is achieved by the passage of a Sodium Chloride saturated solution (table salt).
These cycles, known as Regenerations can be establish manually by the user of the equipment, or automatically either by time elapsed or volume of water produced.
The frequency of these cycles is determined by the relationship between the amount of resin on the tank, the anion content of feed water, and the rate of water flow.
Regeneration by time elapsed indicates that the cycle last a certain amount of hours, after which the resin is regenerated; when it is set to regenerate by volume of water produced, it only occurs when resin is truly saturated for treating all the water it is able to.
This last configuration is safer in terms of maintaining water quality constant, since regenerating by time elapsed, which is independent of the rate of water produced, can lead to a late regeneration, due to an increase in volume of water treated. Untreated water will leave the tank until next regeneration is performed; in contrast with "volume of water treated regeneration" that will always produce treated water.
However, since regeneration happens at the exact moment the resin is saturated, there's the risk that it happens at an hour that treated water is needed, and the equipment is not available. Regenerations last around 90 minutes, depending on the size of the tank, and during this time no water is produced.
A prefiltration chain in recommended in case suspended organic or inorganic matter is present on feed water.