An existing oxidation ditch $($OD$)$ was designed and constructed on the basis of zero

net sludge production to remove organic matter. The design flow of the $($OD$)$ was

$20000\frac{m^3}{d}.$ The design criteria were as follows:

$S_0=285$mgBO$\frac{D_5}{L},$ required effluent concentration $(S)=10$mgBO$\frac{D_5}{L}.$

$Y=0\mathrm{.}50mgvs\frac{s}{m}$gBODs,$Ks=60$mgBO$\frac{D_5}{L},K_d=0\mathrm{.}02d^{-1},{}_m=2\mathrm{.}0d^{-1},$

$x=3000mg$ MLVSS$/$L$.$

A$.$ What is the volume of the OD$?$

B$.$ What is the value of waste activated sludge $"$ Qw $"$ and $(c)?$

C$.$ What would be the value of $"$ S $"$if the flow increased to $40000\frac{m^3}{?}$ day assuming

that X remains $3000m\frac{g}{L}?$ What is your comment on the value of S $?$

D$.$ What are the values of $S,x$ and $\frac{F}{M}$ if we operate the OD on a CFCMR model

instead of Zero net sludge model when the flow increases to $40000\frac{m^3}{?}$ day?

Assume a sludge age value $(c)$ of $25$ days.

E$.$ What are the values of the sludge production" $P_x"$ and sludge waste $"$ Q $"$ for part

$"$D$"$ above assuming $xr=10000mg$ MLVSS$/$ L and $x_e=20mgs\frac{s}{L}?$

Hint: use this equation to calculate $"$Px$"$ for Part E$.$:

$P_x=\frac{Vx}{{}_c}$

And this equation:

to calculate $Q_w.$