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Ammoniacal Nitrogen (NH3)

It is component of nitrogen referred as ammoniacal nitrogen, which is adopted as an indicator to determine pollution by sewage. Other component of nitrogen includes organic nitrogen, Kjeldahl Nitrogen, Nitrate and Nitrite. It is a natural product of decay of organic nitrogen compounds and one of the many contaminants in water supplies.

Ammoniacal Nitrogen is extremely soluble in water, reacting with water to produce ammonium hydroxide and one of the transient constituents in water as it is part of the nitrogen cycle, which is influenced by biological activity. The total nitrogen (TKN) content amounts to about 15% to 20% of the BOD5 in domestic effluent. Appended below is an approximate composition of medium strength domestic wastewater in terms of Nitrogen and its constituents.

Parameter mg/L
Total Nitrogen 35
Kjeldhal Nitrogen 35
Ammonia Nitrogen 25
Organic Nitrogen 10
Nitrate 0
Nitrite 0

There are various sources of ammonia in rivers as follows:-

  • fertilizers for land and agricultural developments.
  • uncontrolled landfill leachate and land development.
  • untreated sewage from poultry farms, reverine squatters, septic tanks, factories, makeshift and toilets at construction sites.
  • wastewater discharges from domestic, commercial, institutional and similar facilities.
  • wastewater and toxic chemicals discharges from different types of industries
  • surface runoff and washouts resulting from rainfall
  • oil, sullage (wastewater) from bathrooms and kitchens
  • municipal sewage treatment plant effluent

Under anaerobic conditions, ammonia is oxidized to nitrite and further oxidized to nitrate through nitrification process. Under anoxic (without oxygen) conditions, nitrate formed is then converted to nitrogen gas with no oxygen present through denitrification.

Excessive ammoniacal nitrogen in waterways can cause taste and (pungent) odor problems, apart from introducing a psychological problem to consumers, who will be under the impression that the water source is contaminated with sewage, even though this is not the case.

The self-purification capability of the waterways is an important concept. By understanding this concept, it will be clear as to why permissible limit of pollutants are discharged to the waterways. Otherwise, excessive discharges of pollutants will "kill" the natural waterways.

Some of the methods used for ammoniacal nitrogen removal are air-stripping (volatilization of gaseous ammonia), breakpoint chlorination (adding chlorine to oxidize ammonia) or ion exchange (type of clay - clinoptilolite for removal of ammonia). It can also be removed from water sources at the raw water intake point or in a wastewater treatment plant. The rate of removal of ammoniacal nitrogen is dependent on the self purification of the waterways/rivers, requirements of the effluent discharge or state of the art technology adopted by potable water treatment plants.

Currently, there is no standard for ammoniacal nitrogen discharge and all existing sewage treatment plants in Malaysia are not designed for the removal of ammoniacal nitrogen. However, on the average, the public sewage treatment facilities comply to the stipulated Standard "A" and "B" requirements as follows:

Parameter Standard A (mg/L) Standard B (mg/L)
Temperature (Celcius) 40 40
pH Value 6.0 - 9.0 5.5 - 9.0
Biological Oxygen Demand 20 50
Chemical Oxygen Demand 50 100
Suspended Solids 50 100
Ammoniacal Nitrogen 15 25

The ammoniacal nitrogen in effluent discharged from sewage treatment plants is gradually diluted in the waterways and is reduced to a less toxic compound

One of the most critical sources of pollution is from septic tanks and pour flush lactrines. There are over 1.2 million septic tanks in Malaysia and only 30% are well maintained i.e. sludge is removed regularly from the tank. Many users of this system neglected their responsibility to ensure that the sludge is removed regularly. Hence, accumulated sludge pollutes the waterways.