There are many disinfection methods in sewage plants, such as chlorination, chlorine dioxide, sodium hypochlorite, ozone, ultraviolet rays, etc. These disinfection methods are used in the design of various sewage plants. These types of disinfection methods have different disinfection principles. Each has its own advantages and disadvantages. The actual use of sewage plants after SARS includes the purchase of raw materials, the cheapness of use, safety, and operating costs. More and more sewage plants are willing to Accept or even modify the use of sodium hypochlorite as a disinfectant in sewage plants. However, many management personnel of sewage treatment plants have a certain lack of knowledge about the disinfection and dosing of sodium hypochlorite in sewage plants. The more common ones are storage, dosage, residual chlorine, and whether the fecal coliform can meet the standards, etc. ; There are also cases of inadequate management. The following will discuss the disinfection work of the sewage plant around sodium hypochlorite.

　　1. The disinfection principle of sodium hypochlorite

　　The effluent of the sewage plant must be disinfected. This is because the municipal sewage contains a large number of microorganisms, including bacteria harmful to humans, protozoan oocysts and cysts, worms, viruses, etc. The inspection workload of many harmful microorganisms is very huge. In order to detect the number of harmful microorganisms in sewage more quickly, the number of fecal coliforms is used as an indicator of the biological hazards of the sewage plant. The sewage plant must carry out corresponding measures before being discharged from the plant. The process is to reduce the number of fecal coliforms to a certain index range, so that the harmful microorganisms in the sewage can be reduced and the environment is acceptable. This is the disinfection of the sewage treatment plant. It should be noted that the disinfection of the sewage treatment plant is not sterilization, only a certain amount of disinfection is sufficient, and sterilization is all killing.

　　There are many other disinfectants commonly used in the disinfection of sewage plants. Sodium hypochlorite is a more commonly used one. Sodium hypochlorite is a kind of chlorine disinfectant. The principle of disinfection is basically the same as that of chlorine. It is through the enzyme ( It is the activity inhibition of the popular "enzyme") to achieve the inactivation and disinfection of microorganisms. The term "available chlorine" is commonly used in chlorine disinfectants to measure the disinfection effect. The mechanism of chlorine disinfection is that chlorine is disinfected by taking the electrons in the organism into Cl- in the water, so the effective chlorine refers to the generation of Cl- from chlorine. However, the Cl chloride ion in sodium hypochlorite (NaClO) is +1 valence, which becomes -1 valence. It takes two electrons, that is, two equivalents of chlorine. Therefore, the effective chlorine content of sodium hypochlorite is:

　　In some literature, the disinfection of chlorine is calculated by using available chlorine, and the available chlorine of sodium hypochlorite is 95.3%. Generally, the sodium hypochlorite prepared by the factory is directly transported to the factory for dosing in sewage plants. The concentration of the sodium hypochlorite solution is between 12% and 15%, which is between 11% and 13% when converted to available chlorine. Therefore, when the wastewater treatment plant is purchasing sodium hypochlorite, do not be misled by some merchants. Generally, it is normal for the effective chlorine to be about 10%. Higher than this value, there are more false ingredients. The higher the concentration of sodium hypochlorite, the easier it is to volatilize. During storage, it is easy to volatilize and reduce the concentration. Pay attention to leaving chlorine release holes on the top of the storage tank, and the storage space must be forced to exhaust to prevent the accumulation of toxic gases. The sodium hypochlorite in the use process of the sewage plant is generally calculated with 10% of available chlorine. The laboratory of the sewage plant can detect the content of available chlorine in the purchased sodium hypochlorite products through the experimental method of the residual chlorine detection iodometric method (GB19106-2013 sodium hypochlorite national standard), which is also a standard testing method for the sewage plant to ensure that the purchased disinfection products are qualified. .