Sewage is the waste generated from residential, institutional, commercial and industrial establishments. STP plant treats the sewage to make it fit for safe disposal, agricultural use or domestic use in toilets etc. Sewage usually contains a high quantity of organic and inorganic wastes. It is essential to treat sewage before it enters into any water body. If sewage, is allowed to enter the water sources without treatment, it will contaminate them; which is why it is essential to treat sewage properly before letting it into rivers or any other sources of water.