$234$

CHAPTER $9$ Sedimentation

table $9\mathrm{.}1$ Percent Suspended Solids Removal at Given Depths

THME $($min$)2$ ft $4$ft $6$ ft $8$ ft $10$ ft $0000001028181812$ a $2048392527$ a $3068503431$ a $4570565341$ a $6085665953$ a $9088827362$ a

$^("$a $")$ Data showed an increase in solids concentration.this is the table to be used for the question above EXAMPLE $9\mathrm{.}1$ Primary Clarifier

A primary clarifier is to be designed to treat an industrial wastewater having $\backslash (320\backslash$mathrm$\{$mg$\}/\backslash$ell $\backslash )$ suspended solids and a flow of $2\mathrm{.}0$ MGD $.$ A batch settling test was performed using an $8-$in$.-$diameter column that was $10$ ft long and had withdrawal ports every $2\mathrm{.}0$ ft $.$ The reduced data giving the percent removals are as shown in Table $9\mathrm{.}1.$

Determine:

$1.$ The design detention time and design overflow rate if $\backslash (65\backslash \%\backslash )$ of the suspended solids are to be removed.

$2.$ The diameter of the tank.

$3.$ The design diameter if equipment is available in $\backslash (5-\backslash$mathrm$\{$ft$\}\backslash )$ increments of tank diameter.

$4.$ The depth of the tank.