Cod is chemical oxygen demand, ammonia nitrogen is nitrogen in the form of ammonia, and COD can be used as a carbon source for some microorganisms to participate in the transformation of nitrogen. They are not directly related, but they are partially related.
COD, that is, chemical oxygen demand, refers to the amount of oxygen (mg/L) consumed by oxidizing organic matter into CO2 and H2O with chemical oxidant (potassium dichromate in China) under acidic conditions, which is expressed by CODcr and abbreviated as COD. Ammonia nitrogen refers to nitrogen in the form of free ammonia (NH3) and ammonium ion (NH4+) in water. There is no connection between the two.
Extended data
The higher the chemical oxygen demand, the more organic pollutants in water, and the more serious the pollution. The nitrogen content of animal organic matter is generally higher than that of plant organic matter. At the same time, the nitrogen-containing organic matter in human and animal feces is unstable and easily decomposed into ammonia. Therefore, when the content of ammonia nitrogen in water increases, it refers to the combined nitrogen in the form of ammonia or ammonium ions.
Determination method of COD: potassium permanganate (KmnO4) method: The oxidation rate is low, but it is relatively simple, so it can be used to determine the relative comparison value of organic matter content in water samples. When COD(KmnO4 _ 4 method) is more than 5mg/L, the water quality has begun to deteriorate. Potassium dichromate (K2Cr2O7) method: It has high oxidation rate and good reproducibility, and is suitable for the determination of total organic matter in water samples.
Generally speaking, the concentration of COD in sewage after secondary biochemical treatment has dropped below 100mg/L, and the concentration of BOD5 is even lower. According to this water quality characteristic, the advanced treatment methods currently used are biochemical method, activated carbon adsorption method and ozone pretreatment+biochemical method.
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