nitrogen in wastewater, removal of nitrogen, significance

1. Presented By : Tulsi Makwana (P17EN011)

2.  Nitrogen is of great importance in water resources, in atmosphere and life process of living
animals and plants.
 Nitrogen exists in seven oxidation states and all are essentially important for environment
engineering is concern.
• NH3 Ammonia
• N2 Nitrogen Gas
• N2O Nitrous oxide
• NO2 Nitrogen Dioxide
• N2O5 Dinitrogen Pentoxide
• NO Nitric Oxide
• N2O3 Dinitrogen Trioxide
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3.  Three forms combine with water and form inorganic ionized species that can reach high
concentrations.
• NH3 + H2O NH4
−
+ OH−
• N2O3+ H2O 2NO2
−
+ 2H+
• N2O5+ H2O 2NO3
−
+ 2H+
 The compounds (Ammonium, Nitrite, nitrate respectively) formed are of environmental
concern for water.
 Other oxidation states, N2(Nitrogen Gas), N2O (Nitrous oxide), NO2 (Nitrogen Dioxide), NO
(Nitric Oxide) exists in gaseous form.
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4. 4

5.  All the nitrogen that exists in the form of ammonium ion is considered as the ammonia
nitrogen.
NH3 + H+ NH4
+
 Methods of analysis:
1. By volumetric analysis : When conc. More than 2 mg/l the conc. can be obtained by
titration with standard solution of sulphuric acid after distillation and absorption of
ammonia in boric acid.
2. By distillation :
3. By ammonia selective electrode.
4. By direct phenate addition.
5. By direct nesslerization.
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6.  All the nitrogen that present in organic compounds is considered as the organic nitrogen in
amino acids, nucleic acids, amines, amides, imides, nitro derivatives, etc.
 Most have very less significance unless special industrial wastes are involved.
 Most of the organic nitrogen that occurs in domestic waste is in the form of proteins or their
degradation products : polypeptides and amino acids.
 Methods applied should ensure measurement without particular regard to other organic forms.
 Once the organic nitrogen gets converted to ammonia nitrogen then the measurement is done
same as ammonia nitrogen.
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7.  Nitrate (NO3) can also be formed in water bodies through the oxidation of other forms of
nitrogen, including nitrite, ammonia, and organic nitrogen compounds such as amino acids.
 Methods of analysis:
1. Screening by ultraviolet spectroscopy : Nitrate ions absorb UV radiation of wavelength
220 nm. Can be used to measure Nitrate.
2. Ion chromatography and capillary ion electrophoresis methods : Useful for nitrate
concentrations greater than 0.2 mg/l.
3. Nitrate electrode method : Can detect concentrations upto 1 mg/l.
4. Cadmium reduction method : Highly sensitive.
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8.  Nitrite (NO2) concentrations are generally less than 1 mg/l, even in wastewater effluents. In
surface and ground water it is low as 0.1 mg/l.
 Methods of analysis:
1. Ion chromatography : generally used but costlier.
2. Colorimetric : cheaper and preferred when nitrite alone is desired, or concentrations are
very low.
3. Photometric measurement.
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9.  In WWTP the first two treatments may remove only 50% of nitrogen concentrations. For
further treatment, lime and HOCl addition were attempted. This however turned out not to be
very effective. Consequently, the third step of wastewater treatment includes biological
nitrogen removal. This means a combination of nitrification and denitrification processes,
carried out by various micro organisms.
 Nitrification means ammonium oxidation from protein decomposition processes by bacteria,
and subsequent conversion to nitrates. This requires oxygen, which is added by aeration.
 Ammonium is converted to nitrite, and subsequently to nitrate.
NH4
+
+ 3O2
−
2NO2
−
+ 4H+ + 2H2O
2NO2
−
+ O2 2NO3
−
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10.  During the denitrification, bacteria decompose nitrates to nitrogen. This does not require
aeration, as it is an anaerobic process. Nitrogen is eventually released into air. A carbon source
is often added to speed up the decomposition process.
 These processes exclude one another, because one requires oxygen and one does not.
Consequently, wastewater treatment requires both aeration, and the presence of oxygen-pour
spaces. When these processes are applied as a third water purification step, approximately 90%
of nitrogen may be removed.
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11.  Ammonia can be removed from water by the so-called stripping process. This means removing
ammonia from wastewater by means of air or steam, by gasifying it.
 Other nitrogen compounds that generally occur in small amounts may be removed by various
methods. For example, NTA (Nitriloacetic acid) can be decomposed under aerobic conditions
in aeration tanks.
 Regular ionic nitrogen compounds, such as NO3
−
, NO2
−
and NH4
+
, and amines, may be removed
by means of ion exchange.
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12.  Aquatic concerns
• Oxidation in rivers and estuaries :
Discharge of ammonia nitrogen in the river and its subsequent
oxidation reduces the dissolved oxygen in the rivers.
• Indicator of Sanitary Quality :
Can say how recently the contamination had occurred. Freshly
polluted water contains nitrogen in the form of organic nitrogen
and ammonia.
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13. • Control of biological Treatment plant :
Determination of nitrogen are often made to control the degree of purification produced by
the biological treatment.
• Nutrition for the organisms :
The nitrogen available in the waste should be sufficient for the organisms. If not then should
be applied from outsides.
• Algal growth.
• High nitrate content leads to Methemoglobinemia.
• Limits : As per EPA, Maximum Nitrate - 10mg/l
Maximum Nitrite - 1mg/l
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14.  Atmospheric concerns
• NOx responsible
• Photochemical smog : Problems due to are eye irritation, low air visibility, crop damage etc.
• Ozone depletion.
• Global warming.
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15. THANK YOU