Question $1$

$($i$)$ Sketch, label and explain all the different parts in activated sludge system used during secondary treatment of wastewater. Give one $(1)$ important purpose each for the return activated sludge $($RAS$)$ and waste activated sludge $($WAS$)$ in an activated sludge system.

$[4+4+2+2$ marks$]$

$($ii$)$ The treated effluent from a primary clarifier is feed in to an aeration tank in $($i$)$ above at a flow rate and concentration of $150000$ gal$/$day and $25m\frac{g}{l}$ respectively. How many pounds of suspended solids leave the aeration tank each day?

$[2+4$ marks$]$

$($iii$)$ List and describe four $(4)$ factors factors that affect the performance of an activated sludge treatment system.

$[2+2+2+2$ marks $]$