GATE CE 2026 Set 1 — Question 21
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Environmental Engineering → Drinking Water Treatment → Filtration
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Question
A rapid sand filter bed of depth m has % porosity during service cycle. It is recommended that during backwash operation, the expanded filter bed should have % porosity. The uniform expanded depth (in m) of the filter bed during backwash is
Correct answer
(D) 1.6
Solution
The volume of solids remains constant during the expansion of the filter bed.
Let and be the initial depth and porosity, and and be the expanded depth and porosity.
Given: m, ,
m.
Thus, the correct option is (D).
Let and be the initial depth and porosity, and and be the expanded depth and porosity.
Given: m, ,
m.
Thus, the correct option is (D).
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