Multiple choice

An ideal horizontal flow setting basin is 3 m deep having surface area 900 m2. Water flows at the rate of 8000 m3/d, at water temperature 20oC (m = 10-3 kg/m.s) and p = 1000 kg/m3). Assuming Stokes law to be valid, the proportion (percentage) of spherical sand particles (0.01 mm in diameter with specific gravity 2.65), that will be removed, is

  1. 32.5

  2. 67

  3. 87.5

  4. 95.5
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The removal efficiency is calculated using the ratio of settling velocity to surface overflow rate. The settling velocity is determined by Stokes Law, and the surface overflow rate is the flow rate divided by the surface area. Comparing these values yields the percentage of particles removed.

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