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.

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

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: