A wastewater treatment plant is where sewage goes from individual households and businesses. It removes a large percentage of the organic wastes (BOD) and sediments from the sewage and then discharges them into a local stream. Even so, the volume of the discharge can still cause a major pollution problem. You can find out more about what is in a wastewater sewage treatment plant at https://en.wikipedia.org/wiki/Sewage_treatment
