Water used in homes and other structures either goes into a septic tank underground or through a sewer system and then into a sewage treatment plant. Water that ends up in sewage treatment plants is treated according to the type of water that it is, while water that is leaving the plant must meet specific quality requirements and may receive other treatments.
Water treated at sewage treatment plants first undergoes a physical process that mainly removes large particles from the water by using screens or filters. The water is then treated with chlorine to help eliminate any harmful microorganisms and bacteria. Other chemicals are also sometimes used in water treatment systems in order reduce the corrosive properties of the water being treated.