Chlorine is the chemical element commonly used to treat water, particularly in municipal water supplies and swimming pools. Its strong disinfectant properties make it effective in killing bacteria, viruses, and other harmful microorganisms, helping to ensure safe drinking water for public health. Chlorine can be applied in various forms, such as gas or hypochlorite solutions, depending on the application and scale. The use of chlorine in water treatment has significantly reduced the incidence of waterborne diseases. However, careful management is essential to prevent potential harmful byproducts that can form when chlorine reacts with organic matter in water.