$(35$ pts$)$ An aerobic biological reactor with the following information is operated for both

carbon removal and nitrification. Biodegradable COD $($bCOD$)$ is found to be removed by

$92\%.$ It is known that all influent nitrogen is biodegradable and the effluent nitrogen of the

aerobic tank is in the form of soluble $N{H}_4-N^2$ and $N{O}_3-N.$

a$.$ Determine the effluent $N{O}_x$ and $N{O}_3-N$ concentration of the aerobic reactor.

b$.$ Determine the total nitrogen $($TN$)$ removal efficiency of the reactor. Do you expect such

a TN removal; briefly discuss the performance of the system in terms of TN removal.

c$.$ Calculate the daily total oxygen requirement of the reactor $(k\frac{g}{d}).$ What percent of the

needed oxygen is for nitrification?

d$.$ Calculate the amount of alkalinity $($ as $CaC{O}_3)$ needed daily, if any.

e$.(10$ pts$)$ If an anoxic tank were operated for denitrification purposes before the aerobic

tank $($i$.$e$.$ leading to an anoxic$-$aerobic sequence$),$ how would the daily alkalinity need,

the oxygen amount daily required and TN removal efficiency change? Increase,

decrease or remain same? Then briefly explain the reason for each parameter asked.

Design flowrate $=5000\frac{m^3}{d}$

$Px,$bio $=250k\frac{g}{d}$

bCOD

$TK{N}_{\text{i}\text{n}\text{f}\text{u}\text{u}\text{e}\text{n}\text{t}}=750m\frac{g}{L}$

$N{O}_3-N_{\text{i}\text{n}\text{f}\text{u}\text{e}\text{n}\text{t}}=40m\frac{g}{L}$

$N{O}_2-N_{\text{i}\text{n}\text{f}\text{l}\text{u}\text{e}\text{n}\text{t}}=0m\frac{g}{L}$

$N{H}_4-N_{\text{e}\text{f}\text{f}\text{u}\text{e}\text{n}\text{t}}=1m\frac{g}{L}$

Temperature $=20C$