A rectangular settling tank is designed for a projected population of $50,000$ people using

the following criteria:

$$ Hydraulic detention time $=2$ hours

$$ Water demand $=0\mathrm{.}75$ m$3/$person$-$day

$$ Surface loading $($i$.$e$.$ overflow$)$ rate $=3\mathrm{.}0$ m$3/$day$-$m$2$

a$)$ Specify required dimensions of settling tank $($assume $3$:$1$ length to width ratio$)$

b$)$ Determine necessary settling velocity for a particle$$s removal in the tank

c$)$ Explain purpose of coagulation$/$flocculation process prior to sedimentation tank