QY $=>$ An activated sludge process is to be designed for

secondary treatment of $8000m^3/$ day of municipal wastewater.

After primary clarification, the BO D of the influent wastewater

is $200m\frac{g}{l}$ which neede to be treated upto $20m\frac{g}{l}.$

MLSS $($Mixed liquor suspended solid$)$ conc" in the reactor is

$3000m\frac{g}{l}$ and in sludge underflow is $10,000m\frac{g}{l}.$ The

mean cell residence time is $10$days. Determine the

underflow volume of the sludge wate.