The velocity of flow of water in a sedimentation tank is about
- A50 to 100 mm/second
- B150 to 300 mm/second
- C150 to 300 mm/minuteCorrect
- D150 to 300 mm/hour
Solution
Concept
Flow velocity in a plain sedimentation tank is kept very low so that particles can settle.
Step-by-step solution
1. Plain sedimentation tanks need very low horizontal velocity. 2. Standard value is about 0.15 to 0.3 m/min. 3. This is 150 to 300 mm/minute.
Explanation
Sedimentation needs quiet water so suspended particles settle down. The usual horizontal velocity is about 150 to 300 mm per minute. Values in mm/second are too fast, and mm/hour is too slow.
Why the other options are wrong
A and B are mm/second, which is far too fast and will scour the settled particles. D (mm/hour) is too slow and not practical.
Shortcut
Remember: 0.15 to 0.3 m/min.
Common mistake
Mixing up units of mm/second and mm/minute.
Correct answer: C) 150 to 300 mm/minute