GATE Civil Engineering (CE) 2020 Shift 1 Solved Paper

Question : 50 of 65

Marks: +1, -0

A water supply scheme transports

10 {MLD}

(Million Litres per Day) water through a

450 {mm}

diameter pipeline for a distance of

2.5 {km}

. A chlorine dose of

3.50 {mg}

/litre is applied at the starting point of the pipeline to attain a certain level of disinfection at the downstream end. It is decided to increase the flow rate from

10 {MLD}

13 {MLD}

in the pipeline. Assume exponent for concentration,

n=0.86

. With this increased flow, in order to attain the same level of disinfection, the chlorine dose

$3.95$
$4.40$
$5.55$
$4.75$

Validate

Solution:

In the disinfection process we have the relationship

t c^{n}=k

where,

{t}=

time required to kill all organism

{c}=

concentration of disinfectant

{K}=

constant

∴ {t}_{1} {C}_{1}^{n}= {t}_{2} {C}_{2}^{n}

\Rightarrow

we know,

{Q}=\;{ {V}}/{ {t}} ⇒ {t}=\;{ {V}}/{ {Q}}

⇒ \;{1}/{10}(3.5)^{0.86}=\;{1}/{13} ×( {c})^{0.86}

⇒ {c}=4.75 {mg} {/} {I}

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