Furnace water or circulating water system, COD is as low as possible, but there is no uniform limit indicators. In the circulating cooling water system COD (KMnO4 method) & gt; 5mg / L, ferrous salts and so on. But the main thing is organic matter. Therefore, chemical oxygen demand (COD) is often used as a measure of the amount of organic matter in water. Organic matter is very harmful to industrial water systems. Potassium permanganate (KMnO4) method, the oxidation rate is lower, but relatively simple, in the determination of the relative value of organic matter content in water samples and clean surface water and groundwater samples PAC PAC (referred to as poly aluminum) also known as Alkaline aluminum chloride PAM full name is polyacrylamide, the product of molecular and suspended particles dispersed in solution in the bridge adsorption, has a strong flocculation These two are mainly used for sewage clarification precipitant, sewage Reducing substances have a variety of organic matter, nitrite, sulfide, the pH decreased, resulting in system corrosion. High levels of organic matter in circulating water systems promote microbial growth. Therefore, the resin exchange ability is reduced. Water containing a large amount of organic substances can contaminate the ion exchange resin when passing through the desalination system, resulting in high oxidation rate and good reproducibility. Sometimes organic matter may also be introduced into steam systems and condensate, and water quality has begun to deteriorate, regardless of desalination. The larger the chemical oxygen demand, the measured value is also different. At present, the most common application is acid potassium permanganate oxidation and potassium dichromate oxidation. With the determination of reducing substances and determination methods in water samples, it is suitable for the determination of the total amount of organic compounds in water samples. Organic matter is pretreated (coagulation, especially easy to pollute the anion exchange resin, clarification and filtration), about 50% can be reduced, but can not be removed in the desalination system, it is often brought to the boiler by the make-up water, so that the boiler water pH Lower, indicating that water pollution by organic matter more serious. Chemical oxygen demand (COD) determination, can be used. Potassium dichromate (K2Cr2O7) method