This story began in the 19th century.
At that time, some cities had established centralized water supply systems, but due to the lack of conventional treatment and disinfection, in some cases, these cities were the cause of disease outbreaks: when pumps and pipes were used to transport water, once it was contaminated, Can spread pathogens in the communities or cities served.
Around 1848, cholera broke out in London. In 2 years, 14,600 people died.
In 1850, John Snow used chlorine for the first time to disinfect water supply. The first attempt to use chlorine to disinfect the water in the BroadStreet Pumping Station in London effectively prevented the spread of cholera in London at that time.
In 1897, typhoid fever broke out in Maidstone, Kent, England. The patient developed persistent high fever, toxic facial features, relatively slow pulse, and roseola, which was life-threatening. Sims Woodhead used "bleach" as a temporary disinfection method in the main pipelines of drinking water, and its effect was surprising. The number of deaths due to typhoid fever has dropped sharply.
In 1908, after the successful implementation of chlorination disinfection technology in London, England, this technology spread to the other side of the Atlantic Ocean. In Jersey City, New Jersey, USA, which was also the first city to chlorinate tap water, the fatality rate of typhoid fever dropped rapidly.
Since then, many cities in the world have begun to promote chlorination technology. In more and more cities, the chlorination of water has been effectively controlled, the mortality rate caused by water-borne diseases has been greatly reduced, people's quality of life has been greatly improved, and the level of public health has also been greatly improved.
This success was reported by Life Magazine in 1997. The article stated: "The filtration of drinking water and the use of chlorine may be the most significant advancement in public health in the past millennium."
Chlorine disinfection has been widely used in the water treatment process. However, because chlorine produces disinfection by-products and fails to effectively inactivate Cryptosporidium oocysts and other factors, many questions have been raised about chlorine disinfection. Disinfection technologies continue to emerge, and new disinfection methods continue to emerge. But now, chlorine is still the mainstream of disinfection work, and chlorinated drinking water supply systems are still the cornerstone of preventing water-borne diseases and protecting public health worldwide.
Drinking water disinfection refers to killing most of the pathogenic microorganisms in the water, including bacteria, viruses, protozoa, etc., to prevent the spread of diseases through drinking water. As mentioned above, typhoid fever is caused by this Salmonella typhi. The disinfection process of drinking water has several main factors that are more important: the type and concentration of microorganisms, the effective disinfectant concentration, and the effective contact time. In addition, the environment The pH (acid-base), temperature, etc. will affect the disinfection effect.
Known chemical disinfection methods for drinking water disinfection include chlorine, chloramine, chlorine dioxide, ozone, and the like.
In addition, the general physical disinfection method is ultraviolet sterilization. It is simple and easy to implement, can effectively inactivate microorganisms in drinking water, has a highly effective killing effect on cryptosporidium, and does not produce harmful disinfection by-products. However, ultraviolet light does not have a long-lasting disinfection effect, and bacteria can easily reproduce in the pipe network. Therefore, simple ultraviolet disinfection is generally used for the situation where water is used immediately after small water treatment (such as disinfection of drinking water in communities and households, and direct drinking water. For disinfection). However, it must be used in conjunction with chlorine when used in large water plants, so there are still certain restrictions on the application of chlorine. Various disinfection technologies have their unique advantages, limitations and costs, and no disinfection technology can be suitable for all situations. The managers and decision makers of the water supply system must comprehensively consider various factors and design a disinfection plan that suits the characteristics, needs, resources, and water quality of each system.
The "Guidelines for Drinking Water Quality" (Fourth Edition) prepared by the World Health Organization (WHO) pointed out that influenza virus and severe acute respiratory syndrome coronavirus (SARS-CoV) are not "pathogens transmitted through drinking water" and are impossible "The level that exists in the water supply."
Moreover, the recent rampant new coronavirus is very sensitive to certain disinfectants, and the specific bactericidal effect and reaction mechanism need to be further studied and demonstrated. The “Guidelines for the Public Protection of New Coronavirus Pneumonia” compiled by the National Health Commission and the National Center for Disease Control and Prevention recently stated that the new coronavirus is sensitive to ultraviolet rays and heat, 56°C for 30 minutes, and ether, 75% ethanol, containing Lipid solvents such as chlorine disinfectant, peracetic acid and chloroform can effectively inactivate the virus, but chlorhexidine cannot effectively inactivate the virus. Chlorine disinfection technology is the main means of urban water supply in our country. Therefore, it is believed that the drinking water treatment process of our water plant can eliminate and inactivate the virus through effective disinfection concentration and effective contact time (CT value), and drinking water is safe.
