COD refers to, under a certain condition, the correspondent mass concentration of oxygen needed in the process of potassium dichromate consumption by the reducible substance oxidized by strong oxidant potassium dichromate in the water, which is represented by mg/L of oxygen. COD can represent the pollution level of the water that is polluted by reducible substances, which involve organics, nitrite, ferrite and sulfide, and so on.
The ammonia nitrogen (NH3-N) in the water refers to the nitrogen existing as free ammonia (i.e. nonionic ammonia, NH3) or ammonium salt (NH4+), which is represented by mg/L. Ammonia nitrogen in the water is produced mainly from the decomposed product of nitrogenous organic compound in the sanitary sewage under the action of microorganism, industrial wastewater like coking synthesis ammonia and the farmland drainage. When the content of ammonia nitrogen is high, the water is toxic to fishes, as well as to human in different levels. Test of the ammonia nitrogen content is helpful for the assessment of water pollution and “self-purification” condition. Thus, ammonia nitrogen is one of the important indicators of water pollution.
Ammonia nitrogen (NH3-N) in the water refers to the nitrogen existing as free ammonia (i.e. nonionic ammonia, NH3) or ammonium salt (NH4+), which is represented by mg/L. Ammonia nitrogen in the water is mainly produced from the process of nitrogenous organic compound in the sanitary sewage being decomposed by microorganism, industrial wastewater like coking synthesis ammonia and the farmland drainage. When the content of ammonia nitrogen is high, the water is toxic to fishes, as well as to human in different levels. Test of the ammonia nitrogen content is helpful for the assessment of water pollution and “self-purification” condition. Thus, ammonia nitrogen is one of the important indicators of water pollution.
