Ozone (O3) is a powerful oxidizing agent that is widely used in water treatment for its ability to remove harmful pathogens and impurities. Ozone is a highly reactive form of oxygen that is made up of three oxygen atoms, and it is created naturally in the upper atmosphere to form the ozone layer that protects the earth from harmful ultraviolet radiation. In water treatment, ozone is used in the form of a gas and is introduced into the water through a process called ozonation. In conclusion, ozone is a powerful oxidizing agent that is widely used in water treatment for its ability to remove harmful pathogens and impurities. Ozone is highly effective at removing bacteria, viruses, and protozoa, as well as dissolved organics, chlorine by-products, and color. Ozone is also effective at breaking down chemical compounds, such as pesticides, herbicides, and pharmaceuticals, that may be present in the water. It is important to test ozone in water to ensure that the water is safe to drink and meets the standards set by regulatory bodies.