A town is required to treat $4.2 \mathrm{~m}^{3} / \mathrm{min}$ 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 $0.2 \mathrm{~mm} / \mathrm{s}$ will produce satisfactory particle removal in a settling basin at a depth of $3.5 \mathrm{~m}$. The required surface area (in $\mathrm{m}^{2}$ ) for settling is

(A) 210

(B) 350

(C) 1728

(D) 21000

A town is required to treat $4.2 \mathrm{~m}^{3} / \mathrm{min}$ 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 $0.2 \mathrm{~mm} / \mathrm{s}$ will produce satisfactory particle removal in a settling basin at a depth of $3.5 \mathrm{~m}$. The required surface area (in $\mathrm{m}^{2}$ ) for settling is

(A) 210

(B) 350

(C) 1728

(D) 21000

127