Civil Engineering - GATE Exam Questions - Discussion

35. 

A water treatment plant is required to process 28800 m3/d of raw water (density = 1000 kg/m3, kinematic viscosity = 10-6 m2/s). The rapid mixing tank imparts tank a velocity gradient of 900s-1 to blend 35 mg/l of alum with the flow for a detention time of 2 minutes. The power input (W) required for rapid mixing is

[A]. 32.4
[B]. 36
[C]. 324
[D]. 32400

Answer: Option D

Explanation:

No answer description available for this question.

Samala Laxman said: (Dec 17, 2013)  
G = sqrt(power input/volume*dynamic viscosity).

Here,
G = 900/sec.
Q = 28800m^3/day = 0.33m^3/sec.
t = 2 min = 120 sec.
Volume = Q*t= 40m^3.
Dynamic viscosity = kinematic viscosity/density.

If we substitute all these values in above formula we will get power = 32400W.

Kirubakara Raj said: (Aug 16, 2016)  
Thanks for your explanation @Samala.

Ruchitamalunjkar said: (Feb 6, 2019)  
Please explain the answer briefly.

Huidrom said: (Jun 28, 2019)  
Dynamic viscosity = kinematic viscosity * Density.

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