$8\mathrm{.}4$ A flocculation basin is to be designed for a

water coagulation plant, and the design flow is

$49,200\frac{m^3}{d}.$ The basin is to be a cross$-$flow hori$-$

zontal$-$shaft, paddle$-$wheel type with a mean velocity

gradient of $26\mathrm{.}7s^{-1}($at $10C),$ a detention time of

$45$min, and a $GT$ value from $50,000$ to $100,000.$

Tapered flocculation is to be provided, and three

compartments of equal depth in series are to be

used, as shown in Figure $8\mathrm{.}19($b$).$ The compartments

are to be separated by slotted, redwood baffle

fences, and the basin floor is level. The $G$ values are

to be $50,20,$ and $10s^{-1}.$ The flocculation basin is to

have a width of $27\mathrm{.}43m$ to adjoin the settling basin.

The paddle wheels are to have blades with a $150-mm$

width and a length of $3\mathrm{.}05m.$ The outside blades

should clear the floor by $305mm$ and be $305mm$

below the water surface. There are to be six blades

per paddle wheel, and the blades should have a

clear spacing of $305mm.$ Adjacent paddle wheels

should have a clear spacing of $760$ to $915mm$ be$-$

tween blades. The wall clearance is $305$ to $460mm.$

Determine:

a$.$ The basin dimensions.

b$.$ The paddle$-$wheel design.

c$.$ The power to be imparted to the water in each

compartment and the total power required for the

basin.

d$.$ The range in rotational speed for each compart$-$

ment if $1$:$4$ variable$-$speed drives are employed.