Activated Sludge

An activated sludge process is being used to treat $1500\frac{m^3}{?}$ day of wastewater containing a BOD concentration of $250g{m}^{-3}.$ Measured parameters for this particular unit are as follows $Y=0\mathrm{.}6(g$ cells$)/($g BOD$)$; $k_m=2\mathrm{.}0($g BOD$)/(g$ cells$)d^{-1}$;$k_d=0\mathrm{.}1d^{-1}$;$K_s=4($g BOD$)m^{-3}.$ Make the typical assumptions for activated sludge modeling $($see pg $350).$

a$.$ Calculate $,$ the mean cell residence time $($units: $d)$ and CMFR volume $($units: $m^3)$ required for $99\%$ removal of BOD for a system involving no cell recycle.

b$.$ Repeat these calculations for a system that recycles $50\%$ of the cells in $10\%$ of the influent flow. Assume the cell separator works perfectly