GATE CE 2016 Set 2 — Question 28
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Environmental Engineering → Drinking Water Treatment → Sedimentation
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Question
A water supply board is responsible for treating of water. A settling column analysis indicates that an overflow rate of will produce satisfactory removal for a depth of . It is decided to have two circular settling tanks in parallel. The required diameter (expressed in ) of the settling tanks is __________
Correct answer
6.8 to 7
Solution
Given:
Total flow rate,
Number of circular settling tanks in parallel,
Overflow rate (surface loading rate),
Depth of settling column, (This is a distractor as the overflow rate depends on the surface area, not the depth)Step 1: Calculate the flow rate per tank ():
Since the tanks are in parallel, the total flow is divided equally:Step 2: Calculate the required surface area () for each tank:
Using the overflow rate formula :Step 3: Calculate the diameter () of the circular tank:
The surface area of a circular tank is given by :The required diameter of the settling tanks is approximately , which falls within the acceptable range of to .
Total flow rate,
Number of circular settling tanks in parallel,
Overflow rate (surface loading rate),
Depth of settling column, (This is a distractor as the overflow rate depends on the surface area, not the depth)Step 1: Calculate the flow rate per tank ():
Since the tanks are in parallel, the total flow is divided equally:Step 2: Calculate the required surface area () for each tank:
Using the overflow rate formula :Step 3: Calculate the diameter () of the circular tank:
The surface area of a circular tank is given by :The required diameter of the settling tanks is approximately , which falls within the acceptable range of to .
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