The following are average operating data from a conventional activated sludge secondary: wastewater

flow $=30,000$ m $3$ d$-1$

$,$ volume of aeration tanks $=8,500$ m $3,$ influent suspended solids $=120$ mg$/$L$,$ influent BOD $=$

$200$ mg$/$L$,$ effluent suspended solids $=10$ mg$/$L$,$ effluent BOD $=10$ mg$/$L$,$ mixed liquor suspended solids $($MLVSS$)$

$=2500$ mg$/$L$,$ recirculated sludge flow $=10,500$ m $3$ d $-1$

$.,$ waste sludge flow $=200$ m $3$ d $-1$

$,$ suspended solids in the waste

sludge $=9800$ mg$/$L$,$ settled sludge volume after $30$ min $=230$ mL$/$L$.$ Based on these data, calculate the following:

$($a$)$ aeration period in hrs; $($b$)$ BOD loading in kg d $-1$ m$-3$

; $($c$)$ F$/$M ratio in mg mg$-1$ d$-1$

; $($d$)$ suspended solids removal

efficiency $(\%),($e$)$ BOD removal efficiency $(\%)$; $($f$)$ sludge age in days; $($g$)$ return sludge rate $(\%)$; $($h$)$ SVI in mL$/$g