Question

A water treatment plant has a flow rate of $0.6m^3/s$. The settling basin at the plant has effective settling volume dimensions of length $20m$ depth $3m$ and width $6m$. What percentage of the particles having a settling velocity of $.004m/sec$ is removed?

• A. 100%
• B. 75%
• C. 92%
• D. 80%

Answer 1

The correct option is D 80%

$\text{Flow rate =}0.6m^3/s$
Surface overflow rate,

$\left(V_0\right)=\frac{Q}{B.L.}=\frac{0.6}{20\times 6}$

$=5\times {10}^{-3}m/sec$

Settling velocity of particle,

$\left(V_s\right)=0.04m/sec$

$\text{\% removal}=\frac{V_s}{V_0}\times 100=\frac{0.004}{0.005}\times 100$

$=80\%$