$8\mathrm{.}8$ An impeller$-$powered flocculation basin is to

be designed for a tertiary treatment plant for a flow

of $94,600\frac{m^3}{d}.$ The plant is to employ alum coagu$-$

lation, and pertinent data for the flocculation basin

are as follows: detention time $=20$min,$G=35s^{-1}$

$($at $10C),GT=10,000$ to $100,000,$ width $=1\mathrm{.}25$

times depth, length $=$ twice width, no baffling,

number of impellers $=2,$ number of blades per

impeller $=6$ pitched at $45,$ impeller diameter $=$

$30\%$ of basin width, $K_L=70\mathrm{.}0,$ and $K_T=1\mathrm{.}65.$

Determine:

a$.$ Basin dimensions.

b$.$ Impeller diameter.

c$.$ Speed of impellers in rpm$.$