Question

The settling basin at a wastewater treatment plant having a flow rate of 0.6 m3/sec has an effective settling volume that is 20 m long, 3 m tall and 6 m wide. what percent of the particles that have a settling velocity of 0.004 m/sec will be removed?:

Answer 1

Let the setting velocity of the basin be v₀ and that of the particles be Vp.

We can calculate the settling velocity as follows:

Volume = base area × height.

Height = volume /base area

Volume in one second = 0.6m³

Base area = 20 × 6 = 120 m²

Height = 0.6/120 = 0.005 m

V₀ = 0.005m/s

Vp = 0.004 m/s

Since the  V₀ is greater than the settling velocity of the particle the particles will all not be removed.

The percentage removed is thus :

(0.004/0.005) × 100 = 80%