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COD description

COD description 2013-3-7

The chemical oxygen demand (COD), is in a certain condition, the adoption of a certain strong antioxidant treatment, water consumption of oxidation dose. It is said that the water reducing matter how much an index. The water reducing agents, there are all kinds of organic matter, nitrite, sulfide, ferrous salt, etc. But the main is organic matter. Therefore, the chemical oxygen demand (COD) and often used as a measure of how much water organic matter content index. Chemical oxygen demand (cod), the water pollution by organic matter that the more serious. Chemical oxygen demand (COD) of measurement, with the determination of water reducing agents and measuring method is different, the measured value also have different. At present, the most common application is acid potassium permanganate oxidation method and potassium dichromate oxidation method. Potassium permanganate (KmnO4) method, oxidation rate is low, but more simple, in the determination of the content of organic matter in water is relative value, can use. Potassium dichromate (K - 2 cr2o7) method, oxidation rate is high, the repeatability is good, suitable for determination of the total amount of organic matter in water. Organic matter to industrial water system of great harm. Contains a lot of organic matter in water by desalination system will pollution ion exchange resin, especially easy to pollution anion exchange resin, resin exchange capacity to reduce. Organic matter after pretreatment (coagulation, clarification and filtering), and can reduce 50%, but in the desalination system which cannot be removed, thus through the make-up water into the boiler, boiler water pH value lower. Sometimes organic matter may also into the steam system and condensation water, make the pH is reduced, cause system corrosion. In the circulating water system of high organic content will promote microbial breeding. Therefore, no matter to the salt, boiler water or circulating water system, COD is as low as possible, but no unified limit index. In the circulation cooling water system of COD (DmnO4 method) > 5 mg/L, water quality has started to variation.

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