Treatment of wastewater involves physical, chemical, and biological processes, which remove physical, chemical and biological matter that contaminates the wastewater. 1)Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removedWater then goes to a grit and sand removal tank. 2)The speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down . 3) The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. 4)A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water