Various steps of cleaning Wastewater in a waste water treatment plant are as follows: 1. Wastewater is passed through bar screen to remove large objects like rags, sticks, cans, plastic packets etc.

2. This water is then passed through grit and sand removal tank to allow sand, grit and pebble to settle down by reducing the speed of the incoming water.

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 which is then transferred to a bio-gas plant for bio-gas production. Here the floatable solids like oil and grease is removed from water by a skimmer. Water so cleared is called clarified water.

4. Then air is pumped into this clarified water to help aerobic bacteria to grow which consume human waste, soap and other unwanted matter still remaining in water. The water is kept undisturbed for several hours so that the suspended microbes settle down at the bottom of the tank as activated sludge and the water is then removed from the top.

5. The treated water is then discharged into a sea or river or into the ground. Sometimes the water is disinfected by chlorine before releasing it into the distribution system.