Nitrates can be found in water supplies that are in areas where there are heavy use of fertilizers. Nitrates can cause Methemoglobinemia a.k.a. blue baby syndrom. This is a serious condition in young infants and new born animals where the oxygen carrying capacity of the blood is reduced.
In applications where higher percentages of nitrate removal are required or where total house treatment is required for a lower cost than whole house reverse osmosis, ion exchange is the best answer.
In the ion exchange process, water containing nitrates is passed through a modified water softener. This special softener contains a resin that is manufactured solely for the purpose of removing nitrates and sulfates in the water. As they are removed they are replaced (exchanged) with harmless chloride. The source of chloride is from the salt used to regenerate the unit which can be either traditional softener salt - sodium CHLORIDE or a special salt called potassium CHLORIDE. Rather than waste either the sodium or the potassium we place the special nitrate resin on top of regular softening resin and along with removing the nitrates and sulfates we also soften the water with the same amount of salt being used. We get a free bonus of softening.
Of particular importance is the proper selection of the nitrate removal resin. It is specially formulated to cling tightly to the nitrates and sulfates until regeneration is required and not let them release into the water in excess amounts --- a process called "dumping". As long as the equipment is functioning, safety is virtually guaranteed. A meter control on the unit is very important to insure that regeneration is done even when unexpected excess water use occurs.