P$2(0\mathrm{.}2570\%$ of the exam$).$ Determine the sludge age, cell wastage flow rate and the return sludge flow rate for the activated sludge tank in the Colp WWTP$.$ Assume:

Suspended solids in the effluent are negligible.

Wastage is taken from the secondary settling tank

Maximum growth rate $=3d^{-1}$

Half saturation constant $=60m\frac{g}{L}$ BOD$5$

Yield coefficient $=0\mathrm{.}40gVS\frac{S}{g}$ BOD$5$ removed

Decay rate $=0\mathrm{.}040d^{-1}$

MLVSS $=1,500m\frac{g}{L}$

MLSS $=1\mathrm{.}40($MLVSS$)$

Solids concentration in the return sludge $=9,000m\frac{g}{L}SS$

Influent BOD$5=150m\frac{g}{L}($soluble$)$

Effluent BOD$5=5\mathrm{.}0m\frac{g}{L}($soluble$)$

Remember that the average design flow is $31,000\frac{m^3}{d}.$