A batch settling test has been performed on an industrial wastewater having an initial

suspended solids of $597$ mg$/$L to develop criteria for the design of a primary clarifier. The test

column was $5$ in$.$ in diameter and $8$ ft high, and sampling ports were located $2,4,6,$ and $8$ ft from

the water surface in the column. The suspended solids remaining after the various sampling

times are given below:

The wastewater flow is $2\mathrm{.}5$ MGD$.$

Determine:

a$.$ The design overflow rate and detention time if $65\%$ percent of the suspended solids are to

be removed. Use scale$-$up factors: $0\mathrm{.}65$ for overflow rate and $1\mathrm{.}75$ for detention time.

b$.$ The diameter if a circular clarifier is used.

c$.$ The design diameter if equipment is available in $5-$ft increments of tank diameter.

d$.$ The depth of the tank.

Time $($min$)$

Depth, ft $1020304560$

$2394352243182148$

$4460406337295216$

$6512429376318306$

$810181142120813151405$