Industries, factories, and mills generate tons of sewage every day. Some of this waste is so harmful that if it is allowed to leave in the neighborhood area it can cause various diseases and contamination of land and water. It is easy to eliminate solid waste but it is not so easy to remove chemical and biological contaminants from these wastes so that they can be sent to safe areas. When sewage is discharged untreated into rivers it becomes dangerous for river animals and human. Therefore, it is necessary to treat sewage before disposing it off in a water body. If waste is not properly treated, then the environment and human health can be negatively impacted. These impacts can include harm to human health, river animals, wildlife populations, oxygen depletion and contamination of drinking water. This contaminated waste is treated with the help of sewage treatment plants.