Water purification includes coagulation sedimentation and sand filtration. Its purpose is to use mechanical and gravity to remove suspended colloidal substances in raw water to improve water transparency and improve its physical and chemical properties; disinfection is to use disinfectants to kill the intestines in the water. Disease microorganisms to prevent the spread and prevalence of water-mediated intestinal infectious diseases.
After the water is treated by coagulation sedimentation and sand filtration, its bacteriological indicators generally still cannot meet the requirements of drinking water quality sanitary standards, so the water must be further disinfected to kill pathogens in the water. When the water source is groundwater, the water quality is transparent and can be directly disinfected without coagulation and sedimentation and sand filtration. There are chlorination disinfection methods, ozone disinfection methods and ultraviolet disinfection methods for drinking water disinfection in water plants. Commonly used is the chlorination disinfection method, the disinfectant used is liquid chlorine or chlorine compounds (bleaching powder, bleaching powder essence, sodium hypochlorite, chloramine-T, calcium hypochlorite).