Show your Work $($sample of calculation$),$ Typed solution is NOT allowed!

Q$1(4$ pt$)$ An AS wastewater treatment system treats $4$ MLD$.$ The CRT is $15$ days. The MLVSS $4000m\frac{g}{l}$ and $xr$ is

$12000m\frac{g}{1}.$ An environmental engineer is to select one of two options based on the lesser amount of wasted stream

$($Qw$)$ :

To directly dispose of the $Qw$ from the bioreactor

To dispose of $Qw$ from the settling unit.

Evaluate each option $($sketch the system for both options$)$ and select the one that require less pumping expenses

Q$2.(7$ pt$)$ A perfectly mixed aeration pond serves as aerobic biological reactor for a small community. The pond

receives $50\frac{m^3}{?}$ day of influent with a COD of $500m\frac{g}{L}$ that must be reduced to $20m\frac{g}{L}$ before discharge. It has

been found that the kinetic constants for the system are $Ks=100$mgBO$\frac{D}{L},{}_{\text{m}\text{a}\text{x}}=1\mathrm{.}6d^{11}$ and $Y=0\mathrm{.}6mg$

bacteria$/$mg COD. Assume steady state conditions and that $x_0=0m\frac{g}{L}$ and $R=0$

a$)$ Calculate the residence time $$ in the aeration pond.

b$)$ The concentration $x$ of the bacteria leaving the aeration pond

c$)$ The mass of the sludge $($microorganisms$)$ that will leave the pond every day.

Q$3(5$ pt$)$ The following is actual data for experimental disinfection on lab scale using Chlorine.

a$)$ Estimate the concentration of disinfectant used in this experiment in

$m\frac{g}{L}($The Chick Watson coefficient of specific lethality ${}_{cw}=1\mathrm{.}8$

L$/$mg$.$min$)$

b$)$ Estimate the contact time required to obtain a reduction of $\frac{1}{25},000$ of the original number of

microorganisms. Assuming that the same concentration of disinfectant as in part a is used.

Q$4.(4$ pt$)$ An ion exchange resin with an exchange capacity of $20e\frac{q}{m^3}$ of $F{e}^{3**}(56\frac{g}{m}ol)$ have $0\mathrm{.}5m^3$ of

resins. The unit treats $10000\frac{L}{d^{\text{w}\text{i}\text{t}\text{h}}}F{e}^{3+}$ content of $75m\frac{g}{F}{e}^{3+}.$ The Ion exchange have a $100\%$ removal

efficiency of TDS$.$

a$)$ How much water $($L$/$d$)$ should be bypassed if it regulation require to have a max of $5mgF\frac{e^{3+}}{1}?$

b$)$ What is the time between regeneration cycle Breakthrough time $($days$)?$

Q$5.(4$ pt$)$ Granular Activated Carbon GAC was to remove Toluene from wastewater. The following adsorption

data were obtained in the laboratory using GAC as adsorhent

a$)$ Determine the maximum adsorbent

phase concentration of adsorbate $Q_{\text{m}\text{a}\text{x}}$

b$)$ Estimate the adsorption constant $K_{ad}$

c$)$ What is the concentration of GAC

$(\frac{g}{m}g)$ needed to remove $40m\frac{g}{l}$ of

Toluene to reach a min of $4m\frac{g}{l}.$