What is Nitrates?

May of one nitrogen and three oxygen atoms, nitrates are commonly used as fertilizer for plants and are the final breakdown product of organic matter in the nitrogen cycle.

If found even at moderate levels, it is generally recommended to test your water for fecal contamination as animal and human waste are common sources of contamination.

High levels in drinking water are not desirable as they affect the oxygen carrying capacity of blood.

The NZ drinking water standards set out a maximum allowable value of 50mg/L, when measured as Nitrate NO3 (When measured as nitrate -N max allowable value is 11.3mg/L).

How do Nitrates get into my drinking water?

Important sources of nitrates are improper disposal of human/animal waste and use of commercial fertilisers.

Shallow wells and bores and those prone to flooding are at higher risk than deeper ones. Care should be taken when drilling new bores that they are far enough away from septic systems and agricultural runoff.

However, it can take decades for nitrates contamination from the source to seep into aquifers, because of this delay in the response of groundwater to changes in soil, some endangered aquifers have not yet

shown the increase expected from the increased use of nitrogen fertilizer or manure. Once the nitrate reaches these aquifers, the aquifers will remain contaminated for decades, even if there is a substantial reduction in the nitrate loading of the surface.

What do nitrates do?

When water containing nitrates is ingested, it is converted to nitrite in the stomach. This can convert hemoglobin in our blood to convert to methemoglobin. This form is unable to release oxygen to the tissues.

In infants this can lead to methemoglobinemia also known as blue baby syndrome This is characterised by blue fingers and lips, and can lead to hypoxia or in more extreme cases, asphyxiation.

Nitrates may also have an effect on the thyroid gland, however exactly how and under what circumstances that occur are still under investigation.

How can I remove nitrates from my water?

Nitrates can be removed from the whole supply using either nitrate specific anion resin or reverse osmosis. At the point of use, reverse osmosis is more economical.