In order to ensure production and life, wastewater monitoring and detection has become a long-term important task in urban planning and governance. The comprehensive sewage discharge standard, that is, the chlorine content (total residual chlorine) in sewage has become an important indicator in sewage treatment. Once it exceeds the standard, it will bring harm to production and life. The specific hazards are as follows. 1. Drinking hazards: After tap water is boiled, it will not cause harm to health. Microorganisms and bacteria have been killed. If the water contains organic decay substances, it will produce carcinogens such as carcinogens after being heated by water. If residual chlorine cannot be removed, heated coffee, tea, and soup will double the number of carcinogens in the human body. Long-term drinking of chlorinated water will lead to heart disease, coronary atherosclerosis, anemia and other symptoms. If pregnant women drink it for a long time, it may have a certain impact on the growth of the fetal heart and lungs, and may even cause arrhythmia and lung dysfunction in newborns. 2. Harm of washing: Bathing with water containing residual chlorine, 40% of the total amount of chlorine in the bathroom is inhaled through the respiratory tract, and 30% is absorbed by the skin, which is several times the amount of chlorine that enters the human body through drinking. Mild cases cause itching , In severe cases, the risk of cancer increases by 30%. Especially when bathing children, chlorine can cause dryness, breakage, and even split ends of the hair, as well as bleaching of the skin, peeling of the skin layer, and even skin allergies. After chlorine is inhaled into the lungs through the respiratory tract, it will damage the respiratory cells and easily lead to asthma and emphysema. 3. Cleaning hazards: How does water containing residual chlorine affect vegetables, fruits, grains, etc.? Chlorine will destroy nutrients such as vitamins in vegetables, fruits, and grains, and seriously affect the absorption of nutrients by the human body. Chlorine combines with natural organic matter in water, especially humus. It is recognized as a carcinogenic, teratogenic, and mutagenic 'three-cause' harmful substance, which is very harmful to the body.