Ozone is not persistent enough to be used up in the pipeline network, and is prone to bacterial growth. Therefore, even if you use ozone to disinfect water, you need to add chlorine residual at the time of water discharge. In addition, China's tap water standards are not lower than those in Europe and the United States, in large cities can basically ensure that the water standard, the water quality can be directly drinkable (but just factory residual chlorine is very high). However, due to the pipe network problems lead to poor water quality at the end of the delivery. The main reason is that ozone needs to generate equipment, relative to liquid chlorine, large investment, energy consumption is also large. Ozone is more often used in the removal of pollutants in the early stage (many water supply plants will be set up before the ozone contact pool, after the ozone contact pool), disinfection with more or liquid chlorine, chloramines are also available, sewage plants also use sodium hypochlorite, sodium hypochlorite to cope with surprise inspections is particularly good ... ... on this topic, followers are roughly divided into three factions, one faction insisted on the "toxic theory! ", pointed out that "the tap water inside the chlorine, heating rice will remain in the rice", and some people say "use pure water to cook rice, rice color and aroma are different"; a faction adhere to the " non-toxic theory", said "chlorine is easy to volatilize", "ate 20 years of tap water to cook rice are fine"; the rest of the majority of people hold the attitude of rather believe it or not, choose to cook with well water or boiled water to seek "safe". The reporter found that the source of this debate is a "don't use tap water to cook food directly, be sure to see" the Internet rumors. Rumor has it that when steaming food, "tap water has chlorine, due to heating the pot lid is covered, chlorine all encapsulated in the food, there is a risk of cancer, so be sure to use boiled water or has been filtered out of chlorine water to steam things. The 'residual chlorine' discussed as potentially harmful to the human body mainly refers to chlorine, and we simulated the normal cooking process at home, using tap water and pure water for cooking respectively, to test the residual chlorine content in the rice-washing water and rice." Dai Ziru, a teacher at the Food Engineering Institute of Qinzhou College, briefly introduced the experimental process to the reporter.