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Nitrogen,
Ammonia, Nitrite and Nitrate
Nitrogen (N)
Nitrogen occurs abundantly
in nature, constituting 78.06 percent, by
volume of the atmosphere. It is also an
essential constituent of proteins in all
living organisms, and is present in many
mineral deposits as nitrates.
In organic matter it undergoes
changes by the decomposition of complex
proteins through amino acids to ammonia,
nitrites and nitrates - and also undergoes
changes by synthesis from nitrates into
more complex organic forms in plants and
animals.
Ammonia (NH3)
In a pure form, it is
a colourless gas with a pungent odour. In
surface or ground waters, it generally results
from the decomposition of nitrogenous organic
matter. However its presence at higher concentrations
could indicate contamination from sewage
waters.
Nitrites (NO2)
In water, nitrites are
generally formed by the action of bacteria
on ammonia and organic nitrogen. As they
are quickly air-oxidised to nitrates, they
are seldom present in surface waters in
significant concentrations.
The presence of nitrite
does not always signify pollution, although,
in conjunction with ammonia and nitrate,
the presence of nitrite is a pollution indicator.
In domestic drinking water supplies, nitrites
are poisonous compounds, but the minute
amounts ordinarily found can scarcely have
any pharmacological effect.
Nitrates (NO3)
They are the end product
of aerobic stabilisation of organic nitrogen,
and as such they occur in polluted waters
that have undergone natural purification
or aerobic treatment. Nitrates also occur
in ground waters as a result of excessive
applications of fertiliser.
High concentrations of
nitrate have been implicated in infant methaemoglobinaemia
(blue baby syndrome), and limits in the
Water Supply Regulations and World Health
Organisation recommendations must be strictly
adhered to.
Treatment
If any of these elements
are identified, the specific cause and concentrations
must be assessed by a Water Chemistry Scientist
before an effective treatment may be recommended.
Nitrate treatment is possible using specific
ion exchange filters, but each case is specific.
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