A complete mix$-$activated sludge processing facility will be designed for the following characteristics:

$Q=5MGD$

Influent BOD $=250m\frac{g}{l}$

Effluent BOD$=20m\frac{g}{l}$

Effluent $SS=20m\frac{g}{l}$

MLVSS in aeration basin $=3500m\frac{g}{l}$

MLVSS in clarifier sludge $=10000m\frac{g}{l}$

Mean cell residence time $=10$ days

Yield coefficient $=0\mathrm{.}6$

Decay rate $=0\mathrm{.}06d^{-1}$

The hydraulic detention time in days: $(5$ pts$.)$

$0\mathrm{.}25$

$0\mathrm{.}5$

$1\mathrm{.}0$

$1\mathrm{.}5$