A water supply board is responsible for treating 1500 m^{3}/day of water. A settling column analysis indicates that an overflow rate of 20 m/day will produce satisfactory removal for a depth of 3.1 m. It is decided to have two circular settling tanks in parallel. The required diameter (expressed in m) of the settling tanks is __________

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GATE CE 2016 Official Paper: Shift 2

CT 1: Ratio and Proportion

2672

10 Questions
16 Marks
30 Mins

__Concept:__

Surface Loading Rate or Surface Over Flow Rate is given by

\({\rm{SLR\;or\;SOR}} = \frac{{{\rm{Discharge}}}}{{{\rm{Surface\;area}}}}{\rm{\;}}\frac{{{{\rm{m}}^3}/{\rm{day}}}}{{{{\rm{m}}^2}}}\)

**Calculation:**

SOR = 20 m/day

Q = Discharge to be treated by two tanks = 1500 m^{3}/day

Discharge to be treated by one tank,

\(Q = \frac{{1500}}{2} = 750\;{m^3}/day\)

\({\rm{SLR\;or\;SOR}} = \frac{{{\rm{Discharge}}}}{{{\rm{Surface\;area}}}}\)

\({\rm{Surface\;area}} = \frac{{{\rm{Discharge}}}}{{{\rm{SOR}}}} = \frac{{750}}{{20}} = 37.5\;{m^2}\)

\( \pi \times \frac{{{d^2}}}{4} =37.5 \)

**d = 6.91 m**