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Q&A on Drinking Water Hygiene 1. What is potable water, and what are the hygiene requirements? Potable water refers to the water used for drinking and daily living purposes. China’s current \"Hygienic Standards for Drinking Water\" (GB5749-2006) set strict hygiene requirements for the quality of drinking water. This includes having good sensory properties, being transparent, colorless, free from any unusual odors, containing no visible particles, and being free from pathogenic microorganisms. The chemical substances present in the water should not cause acute or chronic poisoning or any long-term harm to human health. 2. Why does tap water have a chlorine taste? Chlorine disinfection of tap water is a common disinfection method both domestically and internationally. To maintain the disinfection effectiveness of tap water and prevent microbial contamination during its transmission through the pipeline system to consumers, the residual chlorine level in tap water must be above 0.05 mg/L; as a result, tap water has a chlorine smell. 3. What are the methods of drinking water disinfection? The main methods for drinking water disinfection in our country currently include chlorination with liquid chlorine, disinfection with chlorine dioxide, disinfection with chloramine, ultraviolet disinfection, or ozone disinfection. 4. What are the health requirements regarding the residual amount of disinfectants in drinking water? Different disinfection methods are used for drinking water, and the health requirements regarding the residual amount of disinfectants also vary. If chlorination is used for disinfection, the residual free chlorine or total chlorine in the water at the point of use must not be less than 0.05 mg/L ； If chlorine dioxide is used for disinfection, the residual amount of chlorine dioxide in the water at the point of use must not be less than 0.02 mg/L ； If ozone disinfection is used, the residual ozone concentration in the water at the outlet must not be less than 0.02 mg/L; if chlorination is also applied, the total chlorine content must not be less than 0.05 mg/L. 5. What are disinfection by-products? What are the hygiene requirements? During the disinfection of drinking water, chemical reactions between the disinfectant and certain natural organic substances and environmental organic pollutants present in the water, as well as bromides or iodides, result in the formation of various disinfection by-products. The types of disinfection by-products are related to the methods used for drinking water disinfection; different disinfection methods result in different types of by-products. Currently, the primary method of disinfection for municipal water supply is chlorination, and the main disinfection by-products generated are halohydrocarbons and haloacetic acids. The Hygienic Standards for Drinking Water (GB5749-2006) specify the health requirements for more than 10 such disinfection by-products, including chloroform, bromodichloromethane, dibromochloromethane, dichloroacetic acid, and trichloroacetic acid. 6. Why does tap water appear milky white? When tap water is delivered through high-pressure, sealed pipes, the air in those pipes dissolves into the water due to the high pressure. When the water flows out of the faucet, the air in the water is released as the pressure returns to normal, resulting in countless tiny bubbles that give the water a milky appearance. After a while, the water becomes clear again, with no impact on drinking water safety. 7. Why does drinking water turn yellow? The yellowing is likely due to rust on the inner walls of the iron pipes in the water supply network. Some tap water can be drained, and it can be used again once the water quality becomes clear again. 8. Why does scale form in kettles? The water used in daily life has a certain level of hardness. When such water is heated, the insoluble salt compounds of calcium and magnesium ions (such as calcium carbonate and magnesium carbonate) precipitate out of the water and adhere to the inner surface of the kettle, forming scale. 9. What is secondary water supply, and what are the hygiene requirements? Secondary water supply refers to a method of delivering potable water from centralized water supply systems to users through pipelines, after the water has been stored or reprocessed (such as through filtration and disinfection). The hygiene of secondary water supply facilities must meet the requirements specified in the \"Hygiene Standards for Secondary Water Supply Facilities\" (GB17051-1997). 10. How to avoid drinking water contamination in home renovations? For home renovation, pipes and fittings that come with valid health permits for products related to drinking water hygiene and safety should be used. It is prohibited to connect water supply pipes to other non-potable water pipes. A check valve should be installed when connecting to the toilet. 11. Which laws and regulations does the health department rely on to regulate drinking water? The health authorities carry out health supervision of drinking water primarily based on the Law of the People’s Republic of China on the Prevention and Control of Infectious Diseases, the Measures for the Health Supervision and Management of Drinking Water, and the Health Standards for Drinking Water (GB5749-2006), among other regulations. 12. What are the uniform health requirements for water treatment plants? Water treatment plants must hold a health license as water supply entities, and the drinking water they supply must meet **health standards**. A water source with good quality, sufficient volume, and easy protection should be selected. The water intake points should be located upstream of cities and industrial enterprises. A good standard of hygiene must be maintained within 30 meters of the perimeter of the production areas; residential areas are not allowed, nor should there be toilets or pits that allow water to seep through, nor can garbage, excrement, waste materials be piled up, nor should sewage channels be laid. A water quality testing laboratory must be established to implement quality control throughout the entire process, along with emergency measures for dealing with water pollution. 13. How to choose and use water quality processors correctly? An appropriate water treatment unit can be selected based on the local water quality. Activated carbon and various filter membranes are the main water treatment materials in water quality processors, and they need to be replaced in a timely manner depending on the amount of water filtered. When purchasing, it is also necessary to check whether it has a valid health permit for products related to drinking water hygiene and safety. 14. How to choose and use a water dispenser properly? When purchasing and using a water dispenser, the following points should be taken into consideration: One should buy a water dispenser that comes with a valid health permit issued for products related to drinking water hygiene and safety. Water dispensers need to be cleaned and disinfected regularly, and should not be placed in direct sunlight. Try to drink up the bottled water used in the water dispenser as quickly as possible. 15. What to do if there are abnormalities with tap water? When there are abnormalities in the drinking water, immediately call the 12320 hotline to report the situation to the health supervision authorities, and use the water properly under their guidance, or stop using it. At the same time, the neighborhood committee, property management department, and nearby neighbors should also be informed to stop using it ； Collect 3 to 5 liters of water in a clean container as a sample to be provided to the health inspection department. If contaminated water is accidentally consumed, one should pay close attention to any discomfort in the body. If any abnormalities occur, one should seek medical attention at a hospital immediately. Drinking water can be used again only after receiving an official notice from the **regulatory authorities confirming that the water pollution issue has been resolved. 16. What are the types of decentralized water supply? What should be paid attention to? Decentralized water supply refers to a method in which users draw water directly from the source, with no facilities or only simple ones, such as shallow wells, deep wells, boreholes, spring water, river water, pond water, and well water. In decentralized water supply systems, attention must be paid to disinfection; appropriate disinfectants such as bleach should be added regularly, or the water must be boiled before it can be consumed. Be sure to test the water quality regularly to ensure it is hygienic. Warning signs should be placed at water sources, and necessary sanitary maintenance should be carried out to ensure that the area around them remains free from pollution. It would be best if Asai could be locked up. 17. What is the standard limit for nitrates in drinking water? What should be done once it is found that the nitrate level is above the limit? The Hygienic Standards for Drinking Water (GB5749-2006) stipulate that the limit for nitrates in drinking water (expressed as N) is 10 mg/L, and 20 mg/L when groundwater sources are used. If excessive nitrate levels are detected in the water, the use of that contaminated drinking water should be stopped immediately; this is crucial for infants, breastfeeding mothers, pregnant women, and certain elderly people.