Groundwater is obtained by drilling a well into an aquifer. A well is a hole through the soil that is kept open by placing a pipe in it. If carefully located and responsibly operated, wells allow a community to benefit from the vast supply of water that exists underground. It's the most significant step taken in water treatment. Alone, this step is responsible for all but eliminating diseases such as typhoid, cholera and dysentery.
Chlorine is the chemical added to water for disinfection.
Chlorine is applied in either a gas, liquid or dry form. All raw surface water contains microbes before treatment. Groundwater is usually free from harmful microbes. But by law, all water supplies must be disinfected even if no bacteriological contamination is present. Enough chlorine must be added to drinking water to prevent bacterial growth in the water inside miles of underground pipes in the distribution system that carry water to homes and businesses.