By what methods can we judge which water is drinkable and which water is not drinkable?

(1) Drinking water is taken from groundwater or surface water that meets the sanitary requirements. After purification and disinfection, it is indirectly supplied to people by centralized water supply and decentralized water supply, including tap water and well water. Second, direct drinking water is spring water collected from underground and flowing to the surface, or spring water or deep well water jetted from natural aquifer above natural water level, which meets the hygienic standard for drinking water. Because of the shallow buried depth of groundwater, the contact time with underground strata is short, the flow velocity is unstable and it is easy to be polluted; Although it also contains some minerals and trace elements that are beneficial to human health, the content of these characteristic components has not reached the limited index requirements of mineral water, and there is also a lack of trace elements such as lithium, strontium, selenium, zinc, iodine, bromine and molybdenum contained in mineral water. (2) Pure water refers to the water that can meet the sanitary standard of domestic drinking water by various chemical and physical means, such as distillation, deionization or ion exchange, and other appropriate treatment methods, and is sealed in a container without adding any additives. The genotoxicity of organic extracts from cold water, tap water, natural water and pure water was studied. It is found that the pollution degree of organic matter in pure water is obviously less than that of other three kinds of drinking water. However, while removing bacteria and harmful substances, purified water also removes minerals and trace elements beneficial to human body, thus losing the nutritional function of drinking water. Therefore, drinking pure water for a long time will affect the normal indexes of blood lipid, calcium and magnesium ions, thus inducing cardiovascular system damage. (3) Natural mineral water from deep underground or artificially mined and unpolluted underground mineral water; It is rich in macro and trace elements necessary for human body, as well as minerals or carbon dioxide gas beneficial to human body, and has strong physiological functions; Its chemical composition, flow rate, water temperature and other dynamics are relatively stable within the natural fluctuation range. It does not contain substances harmful to human body or health, and people can drink it directly. 3. Comparison of Hygienic Standards for Drinking Water What are the quality requirements of drinking water, purified water and mineral water from the national technical supervision department? (1) The implementation standard of drinking water is gb 5749-2006 Hygienic Standard for Drinking Water. Relevant standards shall apply to the requirements of drinking water source water: surface water shall meet the requirements of Environmental Quality Standard for Surface Water (gb 3838), which divides surface water into five categories according to environmental function classification and protection objectives. According to the requirements of drinking water source protection, the source water of drinking water should at least reach Class III or above, that is, higher than Class IV; When groundwater is used as water source, it should meet the requirements of Groundwater Quality Standard (gb/t 14848). (2) The implementation standard of pure water is gb 17324-2003 Hygienic Standard for Drinking Pure Water in Bottles (Barrels). (3) The implementation standard of natural mineral water is: GB 8537- 1995 Drinking Natural Mineral Water. The protection of drinking natural mineral water source selection not only meets the requirements of the Hygienic Standard for Drinking Water, but also has its special requirements. For example, the content of main components (total soluble solids, K, na, ca2, mg2, hco3-, so42-2- and cl-) in water quality inspection in wet season, normal season and dry season shall not exceed 20%. The list of quality verification standards for these three kinds of water by the national technical supervision department is as follows: Table 2 Comparative indicators of sensory indicators of drinking water, purified water and mineral water: The chromaticity of drinking water, purified water and mineral water is 155, and turbidity of other colors is not allowed to be displayed15/NTU1~ 315. The smell is not allowed to have peculiar smell, which has the characteristic taste of this mineral water. Nothing visible to the naked eye can be detected without allowing a very small amount of natural mineral salts to precipitate, but it cannot contain other foreign bodies. As can be seen from Table 2, the sensory index is the color and turbidity of water that people can directly feel. The turbidity of pure water is ≤ 1, and the sensory requirement is the highest. The turbidity index of drinking water is 1 ~ 3, and the requirement of mineral water is relatively low. Table 3 Comparison of physical and chemical indexes of drinking water, purified water and mineral water The ph value of drinking water, purified water and mineral water is 6.5 ~ 8.55. 0 ~ 7.0- conductivity (25℃ 1℃)- 10- aluminum/(mg/l) 0.2-l)1. When the oxygen consumption of raw water is greater than 6 mg/L, it is 5-< 3.00 potassium permanganate consumption (O2)(mg/L)- 1.0- volatile phenol (calculated as phenol), mg/l0.002 0.002.