Please pay attention to units $($ITS ML$/$ DAY$)$ detention time cannot be in minutes.

Q$1($a$)$ A water treatment plant has four sedimentation tanks treating $15\mathrm{.}12$Ml$//$ day of water.

Each tank is $4\mathrm{.}9$ m wide, $24\mathrm{.}4$ m long and $4\mathrm{.}6$ m deep. Assuming the weir length is $2\mathrm{.}5$

times the tank width, determine:

$($i$)$ the detention time

$($ii$)$ surface overflow rate

$($iii$)$ horizontal velocity

$($iv$)$ weir loading rate.

$($b$)$ Given a contaminant particle density of $2300$kg$//$m$^(3),$ calculate the diameter of the

smallest spherical particles that would be completely removed.

$($c$)$ Draw a longitudinal section through one of the sedimentation tanks, showing all the

main features and marking clearly the $24\mathrm{.}4$ m length and the $4\mathrm{.}6$ m depth specified

above.