Why is it important to treat water?

To begin with, the water we drink and use in industry and farming is not pure, 100% H2O. In fact, pure water is actually not healthy for human consumption. Although most of the liquid you are drinking is water, some of the other components of the drink include dissolved ions/salts, dissolved gasses, organic matter, and debris. In all of these categories, there are healthy, neutral, unhealthy, and deadly examples. The treatment process is composed of several stages that are designed to remove the latter two categories. First, there is physical filtering of large particles which you wouldn't want to drink - such as twigs and leaves. Then a sedimentation phase removes particles that are small enough to pass through the filter but are not actually dissolved in the water, such as sand. The next stages, flocculation, coagulation, and precipitation involve adding chemicals to the water that attach themselves to unhealthy dissolved impurities and ions (such as calcium and manganese) and form solid precipitates which can easily be removed from the water. Finally, there is a disinfection stage that kills or neutralizes bacteria. Throughout most developed countries, there is a somewhat controversial fluorination stage which adds fluoride to the water for the purpose of strengthening teeth. While universally dentists believe this to be a vital necessity, private citizens are sometimes weary of the government adding chemicals to all the drinking water.