A rectangular sedimentation basin is designed with a water depth $($D$)$ of $3m$ and the $L$ to $W$ ratio is $4$:$1.$ The design flow rate is $54\frac{m^3}{h}r$ and the design residence time is

$0\mathrm{.}5$ hr$.$ Ans: $($a$)L=6m,(b)=6\frac{m}{h}r,(c)=16\mathrm{.}6\%,(d)=L^{\text{'}}=36m$

a$.$ Determine the length $(L)$ of the rectangular sedimentation.

b$.$ Calculate the critical settling velocity in $\frac{m}{h}r($water rising velocity$)$ for the basin

c$.$ If a particle has a terminal settling velocity of $1\frac{m}{h}r,$ calculate the particle removal efficiency $(\%)$ based on parts $($a$)$ and $($b$)$

d$.$ If you desire to achieve complete $100\%$ removal of particles of this size, what adjustment in the length of the basin would be required $($without changing $D$ and W$)?$