3) Determination of Ammonia in drinking water
When nitrogenous organic matter is destroyed by microbiological activity, ammonia is produced and is therefore found in many surface and groundwaters. Higher concentrations occur in water polluted by sewage, fertilisers, agricultural wastes or industrial wastes containing organic nitrogen, free ammonia or ammonium salts. There are two forms of ammonia nitrogen – free ammonia and ammonium ions, depend on the pH.
Ammonia is an indicator for fresh organic pollution of drinking water.
According to Bulgarian Instruction № 9 / 2001 for the quality of water intended for human consumption ammonium ion in drinking water should be no more than 0, 5 mg/l.
Principle of determination
This is a colorimetric method with Nessler’s reagent. The addition of Nessler’s reagent to a water sample will produce a color which ranges from pale yellow to brown depending upon the amount of ammonia present.
Technique
- Measure 5 ml of testing water into the test-tube.
- Add 10 drops of Nessler’s reagent.
- Shake the sample for a few minutes.
- When the color of solution is without change, it is ammonia-free water. In the presence of ammonia in the water sample, the color turns to yellow-orange.