The presence of Nitrates in water causes many problems and high concentrations may cause ( blue baby syndrome ) methaemoglobinaemia  in very young children and to contamination of poultry if used as feed water for farmed birds. The Nitrate is converted to Nitrite in the body which in turn interferes  with oxygen take up in the blood  Over 60% The of high Nitrate is from run off from agricultural land.

Nitrate dissolved in water is not able to be removed by simple filtration. It can only be reduced by either regenerable or disposable cartridge type ion exchange systems or eliminated by Reverse Osmosis. The current regulatory standard for drinking waters is 50 mg/l and Nitrate

Nitrate is removed by an Ion exchange resin system similar to that of water softening using a different polymer resin. The resin removes Nitrate ( and Sulphate due to its chemical similarity ) from the water and replaces them with Chloride ions. Once regenerated like a softener the waste water goes to drain taking away the unwanted Nitrate ions these being replaced by Chloride ions.

Basically the Nitrate removal system is very similar to a water softener. The valved head and controller identical for its use being either a timeclock or water meter. A solution of brine is drawn through the vessel. Sodium Chloride is used as a regenerant. The chloride from the brine displaces the Nitrate and Sulphate ions flushing them down the drain.