In the field of sewage treatment, sodium hypochlorite has become an indispensable treatment agent due to its own chemical properties, playing a key role in multiple treatment links. Its application effectively improves the degree of sewage purification and ensures that the treated water quality meets the safety standards, which is of great significance to the maintenance of the ecological environment and public health.
The most prominent role of sodium hypochlorite is in disinfection and sterilization. Sewage contains a large number of pathogenic microorganisms, such as bacteria, viruses, parasite eggs, etc. If it is discharged directly without treatment, it will pose a serious threat to the environment and human health. Sodium hypochlorite will hydrolyze in water to produce hypochlorous acid. Hypochlorous acid has strong oxidizing properties and can penetrate the cell membrane of microorganisms, react with proteins, nucleic acids and other substances in the cells, destroy their structure and function, and thus quickly kill microorganisms. Whether it is the common Escherichia coli and Salmonella in domestic sewage, or the special pathogenic bacteria that may exist in industrial wastewater, sodium hypochlorite can play a strong disinfection role, greatly reducing the number of pathogens in sewage, so that it meets the discharge standards and avoids the risk of disease transmission.
In addition to disinfection, sodium hypochlorite can also be used to remove odors from sewage. The odor in sewage mainly comes from the decomposition of organic matter and sulfur-containing compounds such as hydrogen sulfide and ammonia. Sodium hypochlorite has strong oxidizing properties and can react chemically with these odor-producing substances to oxidize them into harmless and odorless substances. Taking hydrogen sulfide as an example, sodium hypochlorite can oxidize it into sulfate ions, thereby eliminating the pungent smell of rotten eggs; for nitrogen-containing compounds such as ammonia nitrogen, sodium hypochlorite can oxidize them into nitrogen or nitrates, effectively removing the irritating odor in sewage and improving the quality of the surrounding environment.
During the sewage treatment process, some sewage contains organic pollutants that are difficult to degrade, which will affect the discharge of sewage in compliance with standards. Sodium hypochlorite can decompose these complex macromolecular organic matter into small molecular substances through oxidation, thereby improving the biodegradability of sewage. After pretreatment with sodium hypochlorite, the subsequent biological treatment process can degrade organic matter more efficiently, further reduce the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in sewage, and purify sewage more thoroughly.
Sodium hypochlorite can also be used to remove color from sewage. The color of sewage is usually caused by some colored organic matter, metal ion complexes, etc., which seriously affect the appearance of water quality. The strong oxidizing property of sodium hypochlorite can destroy the molecular structure of these color-developing substances, making them lose their color-developing ability. Whether it is the dye pigment in printing and dyeing wastewater or the color caused by impurities in other industrial sewage, sodium hypochlorite can play a decolorizing role to a certain extent, making the treated sewage clear and transparent, achieving better visual effects and water quality standards.
In the deep treatment stage of sewage, sodium hypochlorite also plays an important role. When the requirements for sewage reuse or discharge water quality are high, the sewage after conventional treatment may still contain a small amount of residual pollutants. At this time, adding sodium hypochlorite can further remove these trace impurities and ensure that the water quality reaches higher standards. For example, in the reuse of reclaimed water, sodium hypochlorite can effectively kill residual microorganisms, reduce the total number of bacteria and virus content in the water, prevent secondary pollution during the reuse process, and ensure the safety of reclaimed water in reuse scenarios such as landscape water use and road spraying.
However, when using sodium hypochlorite to treat sewage, it is also necessary to pay attention to its potential impact. Sodium hypochlorite itself is corrosive to a certain extent. If used improperly, it may cause corrosion damage to sewage treatment equipment and shorten the service life of the equipment. In addition, if the dosage of sodium hypochlorite is not well controlled, excessive sodium hypochlorite may react with certain substances in sewage to generate harmful byproducts, such as trihalomethanes and other disinfection byproducts. These substances are toxic and carcinogenic, and instead cause new harm to the environment and human health. Therefore, in practical applications, the dosage of sodium hypochlorite must be accurately controlled, and subsequent monitoring and treatment work must be done well.
Sodium hypochlorite plays an important role in the sewage treatment process, from disinfection and sterilization, odor removal, to degradation of organic matter, decolorization, and deep treatment, which significantly improves the effect and quality of sewage treatment. However, during use, its characteristics should be fully considered, and the use conditions and dosage should be reasonably controlled to avoid negative effects, so as to better play the advantages of sodium hypochlorite in sewage treatment and achieve efficient purification and safe discharge of sewage.
