Question

A town is required to treat $4.2m^3/min$ of raw water for daily domestic supply. Flocculating particles are to be produced by chemical coagulation. A column analysis indicated that an overflow rate of 0.2 $mm/s$ will produce satisfactory particle removal in a settling basin at a depth of 3.5 m. The required surface area (in $m^2$) for settling is

• A. $1728$
• B. $350$
• C. $21000$
• D. $210$

Answer 1

The correct option is B $350$

Water required for daily domestic supply,

$Q=4.2m^3/min$

$=\frac{4.2m^3}{60s}$

Surface overflow rate,

$SOR=0.2mm/s$
$=0.2\times {10}^{-3}m/s$

Surface area required, $A=\frac{Q}{SOR}=\frac{4.2}{60\times 0.2\times {10}^{-3}}$

$=350m^2$