Dear Carlos, The WHO ...

Dear Carlos,

The WHO Guideline Value is 50mg/l nitrate - the following document should be useful; http://www.who.int/water_sanitation_health/dwq/chemicals/nitratenitrite2ndadd.pdf

In terms of consumers, it is formula (bottle) fed infants that are at greatest risk - high nitrates can in rare cases cause blue-baby syndrome - the above document will have further information on this.  For other age groups elevated nitrate is generally not an issue.

There are various ways of reducing nitrate;

1).  Nitrate exchange - this uses a resin-based media that exchanges the nitrate ion for chloride.  It is a very common process and should be easily available.  The issue is that depending on the volume needing to be treated it could be quite costly.  Excess chloride may also be problem, particularly if the ground water is saline influenced.

2).  Blend-treating with a low nitrate source.  This is also very common but requires a low-nitrate source to be available.  Careful control/blending/monitoring would be needed to ensure the nitrate remains under the GV.  As a note, I've known nitrate levels to vary significantly in groundwater sources that are relatively close.

3).  Identifying (and removing) the source of the nitrate.  This is a longer term solution and probably not practical but worth being aware of.  Nitrate in groundwater will typically come from sources such as sewage disposal to ground and agricultural practices; if changes can be made to reduce such harmful practices close to water abstractions eventually the nitrate should reduce (although can be a very large area).

Kind regards, Andy