Question

For a flow of $5.7MLD$ (million litres per day) and a detention time of 2 hours, the surface area of a rectangular sedimentation tank to remove all particles having a settling velocity of 0.33 $mm/s$ is

• A. $200m^2$
• B. $20m^2$
• C. $400m^2$
• D. $100m^2$

Answer 1

The correct option is A $200m^2$

Surface area of tank = $B\times L$

For 100% efficiency,

$V_s=V_0$

$V_0=\frac{Q}{BL}$

$BL=\frac{Q}{V_0}$

$=\frac{5.7\times {10}^6\times {10}^{-3}}{24\times 60\times 60\times 0.33\times {10}^{-3}}$

$=199.91m^2$

$\simeq 200m^2$