Question

Some students of class 7 were taken for an educational trip to Waste water treatment plant .The teacher explained the process of water treatment. Identify the correct order of the process.

Step I:The liquid material is passed through sedimentation tank where solid waste like faecal matter, sand, grit settles down.

Step II:This solid matter is then removed with the help of a scrapper. This is the sludge.

Step III: Waste water is passed through bar screens to remove big objects like cans, sticks, rags etc.

Step IV: A skimmer removes the floatable solids like oil, grease etc.

Step V: Air is pumped into clarified water to help aerobic bacteria to grow. The bacteria then consume the unwanted matter still present in clarified water.

Step VI: The clear water so obtained is called clarified water.

Step VII:The suspended microbes settle at the bottom & the water is removed from the top.

• A. III, I, II, IV, VI, V, VII
• B. III, I, II, IV, V, VII, VI
• C. I, II, III, IV, VI, V, VII
• D. I, II, III, IV, V, VI, VII

Answer 1

The correct option is A

III, I, II, IV, VI, V, VII

There are various steps involved in the water treatment plant which involves physical, chemical & biological processes. The correct sequence of all the processes involved is given below-

• Waste water is passed through bar screens to remove big objects like cans, sticks, rags etc.

• The liquid material is then passed through sedimentation tank where solid waste like faecal matter, sand, grit settles down.

• This solid matter is then removed with the help of a scrapper. This is the sludge.

• A skimmer removes the floatable solids like oil, grease etc.

• The clear water so obtained is called clarified water.

• Air is pumped into clarified water to help aerobic bacteria to grow. The bacteriathen consume the unwanted matter still present in clarified water.

• The suspended microbes settle at the bottom & the water is removed from the top.