b A complete mixed activated sludge process aeration tank for

treatment of $4$ MLD sewage having BOD concentration is $180$

$m\frac{g}{L}.$ The effluent should have BOD of $20m\frac{g}{L}.$ Consider

MLVSS$/$MLSS $=0\mathrm{.}8.$ Return sludge MLSS concentration $-$

$10000m\frac{g}{L}.$ MLVSS in aeration tank $=3500m\frac{g}{L}.$ Mean cell

residence time adopted in design is $10$ days, reactor volume is

$571\mathrm{.}14m^3$ and $f=0\mathrm{.}68.$ Calculate the following

$($i$)$ Treatment efficiency $($ii$)$ F$/$M ratio$($iii$)$ Hydraulic residence

time $($iv$)$ Volumetric loading v$)$ Sludge waste volume Total

oxygen requirement $($considering the some portion of the

substrate is utilized for synthesis of new bio$-$mass$)$