Question -
Answer -
Step 1: When wastewater passes through bar screens, large objects like rags, sticks, cans, plastic packets are removed.
Step 2: Water then goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down.
Step 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 scraper.
Step 4: Air is pumped into clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soap and other unwanted matter that still remains in clarified water.
After several hours, the suspended microbes settle at the bottom of the tank as activated sludge. The water is then removed from the top.