Q:$22$ Compute the mean cell residence time and recirculation ratio and volume of a reactor from the following data to design a conventional activated sludge process. Compare the recirculation ratio if the effluent biomass concentration of $15m\frac{g}{L}$ is considered in the mass balance analysis.

Given data:

$($i$)$ Daily average wastewater flow Qavg$=20$MLD

$($ii$)$ Sludge wasting flow $=140\frac{m^3}{d}$

$($iii$)$ Biomass concentration in reactor $x=4000m\frac{g}{L}$

$($iv$)$ Returned Sludge Concentration $xr=10,000m\frac{g}{L}$

$($v$)$ Hydraulic retention time $=4hrs.$