Nitrate is a very soluble substance, easily dissolved in water and extremely hard to remove. Treatment for nitrate is, therefore, very complicated and expensive. The three methods of reducing or removing nitrate are: ( 1) demineralization by distillation or reverse osmosis; (2) ion exchange; and (3) blending.
Demeralization removes nitrate and all other minerals from the water. Distillation is one of the oldest, most effective types of demineralization. The distilling process has only three steps: 1) the water is boiled; 2) the resulting steam is caught; and 3) the steam is condensed on a cold surface, turning back into water. The nitrate and other minerals remaim concentrated in the boiling tank.
Reverse osmosis is another way to demineralize water. In a reverse osmosis system, the water is put under pressure and forced through a membrane that filters out minerals and nitrate. One-half to two-thirds of the water remains behind the membrane as rejected water. The yield of treated water to reject water is related to the amount of pressure applied; the lower the water pressure, the greater the volume of reject water. Higher-yield systems use water pressures in excess of 150 psi. The systems that operate using standard household water pressure (35-45 psi.) will yield some treated water, but a large amount of untreated water goes down the drain. Household units are usually small enough to fit under the sink or on a kitchen counter.
Both of these demineralization systems require a lot of energy to operate efficiently. They are also low-yield systems that may provide enough water for a family, but cannot produce the large quantities needed for livestock.
The second type of water treatment for nitrate contamination is ion exchange. Ion exchange introduces another substance that "trades places" with the nitrate. Most often chloride is exchanged for nitrate. The ion-exchange unit is a tank filled with special resin beads that are charged with chloride. As water containing nitrate flows through the tank, the resin takes up nitrate in exchange for chloride. In time, all the chloride will be exchanged for nitrate. The resin can then be recharged by backwashing with a brine solution (sodium chloride) and reused.
Because ion-exchange systems can treat large volumes of water, they are more appropriate than demineralization for treatment of livestock water supplies. There are, however, some drawbacks to ion-exchange systems. First, in addition to exchanging nitrate, the resin beads will also take up sulfate in exchange for chloride. Therefore, if sulfates are present in the water supply, the capacity of the resin to take up nitrate is reduced. Second, the resin may also make the water corrosive. For this reason, the water must go through a neutralizing system after going through the ion exchange unit. Finally, the backwash brines, which are high in nitrate, must be disposed of properly so they do not recontaminate the groundwater supply.
The third and most common way to reduce nitrates is to dilute the nitrate-polluted water by blending it with water from another source that has low nitrate concentrations. Blending the two waters produces water that is low in nitrate concentration. Blended water is not safe for infants but is frequently used for livestock.
There is no simple way to remove all nitrate from your water. Although it is common to think of boiling, softening or filtration is a means of purifying water, none of these methods reduce nitrate contamination. Boiling water is ,in fact, the worst thing to do because it actually concentrates the nitrate. Softening and filtration do nothing at all to remove nitrate.