Question

Consider the following statements:

1. Ammonia nitrogen is a measure of nitrogen present as ammonium hydroxide and ammonium salts. It will progressively decrease as sewage gets treated.

2. Organic nitrogen is the total nitrogenous matter in sewages excepting that present as ammonia nitrogen, nitrites and nitrates. It becomes ammonia in anaerobic decomposition and nitrites or nitrates in aerobic decomposition.

Which of the above statements is/are correct?
1. 1 only 
2. Both 1 and 2
3. 2 only 
4. Neither 1 nor 2

Answer 1

Correct Answer - Option 2 : Both 1 and 2

Concept:

Nitrogen Contents in sewage: The presence of nitrogen in sewage indicates the presence of organic matter, and may occur in one or more of the following forms: Free ammonia (also called Ammonia nitrogen), Albuminoid nitrogen (also called Organic nitrogen), Nitrites and Nitrates.

Free ammonia (or Ammonia nitrogen): Ammoniacal nitrogen (NH₃-N), is a measure for the amount of ammonia present in sewage. Ammonia has chemical formula of NH₃ in the unionized state and NH₄⁺ in the ionized state. The ammonia nitrogen is the sum of nitrogen present in both NH₃ and NH₄⁺. The free ammonia indicates the very first stage of decomposition of organic matter and the amount will progressively decrease as sewage gets treated.

Albuminoid nitrogen (or Organic nitrogen): Organic nitrogen is that nitrogen which describes nitrogen compounds that had its origin in living material. The nitrogen in protein and urea is organic nitrogen. Organic nitrogen can enter sewage as bodily wastes, discarded food material, or as components of cleaning agents. This albuminoid nitrogen indicates quantity of nitrogen present in sewage before the decomposition of organic matter is started. If this organic nitrogen reacts anaerobically then it decomposes to ammonia and if this reacts aerobically it converts to nitrites or nitrates.