Civil Engineering - Water Supply Engineering - Discussion

14. 

Flow through period, in sedimentation tanks, is

[A]. equal to detention period
[B]. more than detention period
[C]. less than detention period
[D]. detention period divided by displacement efficiency
[E]. none of these.

Answer: Option C

Explanation:

No answer description available for this question.

Samm said: (Oct 13, 2016)  
I can't find the difference between two, someones please help to differentiate.

Saravanan said: (Jul 26, 2017)  
I think more than the detention period.

So please clarify me.

Preetam Singh said: (Oct 11, 2017)  
This option is wrong. Flow through period should always be equal or greater than the detention period so that all the suspended particles having detention period can easily settle.

Avinash said: (Dec 28, 2017)  
Yeah, this answer is wrong as flow through period should be more to avoid any short-circuiting in the system and to avoid travel of objectionable particles to further units.

Anuj said: (Mar 5, 2018)  
Flow through period is the period "during this period the particles in suspension settle down and clear water flows out continuously from the tank. ".

Detention period -- Time taken by water to pass between entry and exit.

So the time taken to settle down i.e. flow through time should be larger than detention period. Hence, answer is correct.

Pankaj Pj said: (Apr 30, 2018)  
Flowing through period is the time taken by a batch of water to travel from the entry to exit of settling tank. Because of short circuits produced in water current, flowing through period is less than the detention period.

Chirag Verma said: (May 28, 2018)  
Displacement efficiency = (flow through period/theoretical detention time )*100.

Rishav Baishya said: (Jul 7, 2018)  
Detention time is calculated on basis of geometry, but in actual, there is turbulence at the top layer and drag, friction at the bottom layer, which are not considered in calculations. So the top layer has more velocity so detention timeless so unable to settle and the bottom layer has less velocity so detention time more and easily settle. Practically the average detection time called the flow through period is less than the geometrically calculated detention time.

So, given answer is correct.

Amarnath said: (Sep 29, 2018)  
The answer given is right if you consider comparison between Settling velocity and flow velocity.

Vidya said: (Dec 2, 2018)  
Displacement efficiency is the ratio of flowing through the period to the detention period. Flowing through period is the time taken by a batch of water to travel from the entry to exit of the settling tank. Because of short circuits produced in the water current, flowing through period is less than the detention period. So, the given answer is true.

Sindhu said: (May 31, 2019)  
Flow through period should be less than the the detention time so that the particles can settle down. If it is greater than the detention time then particles won't get a chance to settle down.

Vipul said: (Aug 2, 2019)  
Flowing through period is the time taken by a batch of water to travel from the entry to exit of settling tank. Because of short circuits produced in water current, flowing through period is less than the detention period.

Aravind said: (Aug 17, 2019)  
Settling time or flow through time should be less than or equal to detention time for 100% removal efficiency.

Badhon said: (Oct 27, 2019)  
What is the ideal value of displacement efficiency? is it 1?

Lalit said: (Dec 28, 2019)  
Displacement efficiency = (flow through period/theoretical detention time )*100.
Flow through period Decreases theoretical detention time increases.

Abdullah said: (Apr 27, 2020)  
Displacement efficiency = (flow through period/theoretical detention time) *100.

Flow through period Decreases theoretical detention time increases.

Zeenat said: (Dec 13, 2020)  
Flowing through period is the time taken by a batch of water to travel from the entry to exit of settling tank. Because of short circuits produced in water current, flowing through period is less than the detention period.

Sathya Siva said: (Jul 26, 2021)  
Settling velocity must be more than overflow velocity.

Hapster said: (Aug 15, 2021)  
Flow through period is always less than the detention time due to short circuiting.

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