What is the standard of healthy drinking water?

Drinking water is an indispensable factor for human survival and is closely related to people's daily life. Drinking water sources for urban residents are provided by water supply companies. Generally speaking, the quality of water quality depends on the quality of centralized water supply, and individuals cannot choose. Therefore, in order to ensure the provision of safe and hygienic drinking water for residents, the Ministry of Health of China has promulgated the Hygienic Standard for Drinking Water, which is a technical regulation on the safety and hygiene of drinking water and has played an important role in ensuring the quality of centralized water supply in China. Drinking water refers to water used for human consumption and daily life, including personal hygiene, but excluding water used for aquatic organisms and special purposes. The formulation of Hygienic Standard for Drinking Water is based on the safety of people's lifelong water use. Ensuring the safety and hygiene of drinking water is mainly based on three aspects, namely, ensuring good sensory characteristics of drinking water; Prevent the outbreak of water-borne infectious diseases; Prevent acute and chronic poisoning and other health hazards. There are four kinds of indicators to control the hygiene and safety of drinking water: microbial indicators Water is an important medium for spreading diseases. Pathogens in drinking water include bacteria, viruses, parasitic protozoa and worms, and their pollution sources are mainly human and animal feces. In underdeveloped countries, it is very common that drinking water causes the epidemic of infectious diseases. This may be due to the incomplete disinfection of the water source after being contaminated by pathogens, or it may be caused by the secondary pollution of drinking water during the transportation and storage of water. The ideal drinking water should not contain known pathogenic microorganisms, nor should it contain indicator bacteria contaminated by human and animal excreta. In order to ensure that drinking water can meet the requirements, it is very important to regularly sample and detect the indicator bacteria of fecal pollution in water. Therefore, the indicator bacteria specified in the Hygienic Standard for Drinking Water in China is the total coliform bacteria, and the index of free residual chlorine is also specified. Chlorination disinfection is widely used in waterworks in China. When the free residual chlorine in drinking water reaches a certain concentration, it can kill bacteria and viruses in water after contact for a period of time. Therefore, the determination of residual chlorine in drinking water is a rapid and important index to evaluate the microbial safety of drinking water. Sensory characteristics and general chemical indicators of water The sensory characteristics of drinking water are very important. Water with bad sensory traits will make people feel disgusted and insecure. China's drinking water standard stipulates that the chromaticity of drinking water should not exceed 15 degrees, that is to say, ordinary drinkers should not notice that water is colored and cannot have abnormal smell and taste. Water is transparent, not turbid, and there are no foreign bodies visible to the naked eye. If the drinking water is found to be turbid, with abnormal color or taste, it means that the water quality is polluted, and the water supply company and the health and epidemic prevention station should be notified immediately for investigation and treatment. Other chemical indexes related to the sensory characteristics of drinking water include total hardness, iron, manganese, copper, zinc, volatile phenol, anionic synthetic detergent, sulfate, chloride and dissolved total solids. These indicators will affect the appearance, color, smell and taste of water, so the maximum allowable limit is stipulated. For example, the sulfate in drinking water is too high, which is easy to scale in boilers and water heaters, resulting in bad taste of water and laxative effect, so the limit value of sulfate in drinking water cannot exceed 250 mg per liter. Toxicological indicators With the development of industry and science and technology, people pay more and more attention to the pollution of drinking water by chemical substances. According to foreign investigations, hundreds of chemicals have been identified in drinking water, most of which are organic compounds. Toxic chemical pollution in drinking water is different from microbial pollution in its harm to health. Generally speaking, microbial pollution will cause the outbreak of infectious diseases, and the health problems caused by chemical substances are often due to the harmful effects caused by long-term contact, especially the accumulated poisons and carcinogens. Only under very special circumstances can a large amount of chemical pollution cause acute poisoning. In order to ensure the safety of drinking water, it is necessary to determine the maximum allowable limit of chemicals in drinking water, that is, the maximum allowable concentration, which is an important basis for water companies to provide safe drinking water to the public. However, there are many chemicals in drinking water, which chemicals should be chosen as the index to determine the limit? This is mainly based on the toxicity of chemicals, the concentration and detection frequency of drinking water, and whether there is enough basis to determine the limit. In the Hygienic Standard for Drinking Water in China, * * * selected 15 chemical indexes, including fluoride, chloride, arsenic, selenium, mercury, cadmium, chromium (hexavalent), lead, silver, nitrate, chloroform, carbon tetrachloride, benzo (а) pyrene, DDT and bhc. The limit values of these substances are based on the data obtained from toxicological research and population epidemiological investigation. Radioactivity indicators Some practical activities of human beings may increase the natural radiation intensity in the environment, especially with the development of nuclear energy and the application of new isotope technology, it is likely to cause environmental pollution by radioactive substances. Therefore, it is necessary to routinely monitor and evaluate the radioactive indicators in drinking water. The reference values of total α radioactivity and total β radioactivity are specified in the Hygienic Standard for Drinking Water. When these indexes exceed the reference value, a comprehensive radionuclide analysis is needed to determine the safety of drinking water.