Sedimentation basin in a water treatment plant is designed for a flow rate of 0.2 m3/s. The basin is rectangular with a length of 32 m

Q. Sedimentation basin in a water treatment plant is designed for a flow rate of 0.2 m³/s. The basin is rectangular with a length of 32 m, width of 8 m, and depth of 4 m. Assume that the settling velocity of these particles is governed by the Stokes’ law. Given: density of the particles = 2.5 g/cm³; density of water = 1 g/cm³; dynamic viscosity of water = 0.01 g/(cm.s); gravitational acceleration = 980 cm/s². If the incoming water contains particles of diameter 25 μm (spherical and uniform), the removal efficiency of these particles is

(A) 51%

(B) 65%

(C) 78%

(D) 100%

Ans: 65%

Solution:

Given:

Flow rate = 0.2 m3/sec
Dimension of tank = 32m×8m×4m
Density of particles= 2.5 g/cc
Density of water= 1 g/cc
Dynamic viscosity of water = 0.01 g/cm.s
Diameter of particle = 25 μm

We know that Over flow rate of tank