When force mains leak, they leak out. A force main leak, like a water main leak, becomes immediately evident by the flow of water from the ground. Force mains often carry the wastewater directly to the treatment plant. That water must go somewhere. The purpose of sewage treatment is to remove the harmful substances from the water so that it may be re-introduced into the environment without causing public health or environmental problems.
Sewage contains many substances that are harmful to people and animals and the environment.
In general they can be classified in the following groups. Organic substances, including fecal matter, kitchen wastes and laundry waste. Bacteria and micro organisms. Nitrogen and phosphorous compounds that promote plant growth. Toxic substances contained in cleaning compounds, disinfectants and industrial wastes.