$(4)$ The WWTP in the $\text{'}$AA$\text{'}$ communty discharges $10$ million gallons $($ day

of secondary effluent into a skeam "Red Cedar" $.$hose minimum

flow wak $i$ i $100\frac{m^2}{s}.$

Given that temp of wW PP effluent $2$ sheam wath an $20C815C,$

BoDs $-20$ of wwTP effluent and sheam wher is $200m\frac{g}{C}$Cim$\frac{g}{L}$

serputively. And Do of wWTP effluent is $Ln\frac{g}{c}$ and that of stean evathe

effluat is $80\%$ of suturation level. Finther oxygen couqumption vate is $0\mathrm{.}3H^{-1}$

and oxpgen reaeration rate is $0\mathrm{.}7t^{-1}.$

Uning above information, calculat the following:

$(1)$ Tomp, DO ane BOD of the mixture

$(2)$ Anithal Do at the place of mixing

$(3)$ Critical oxjyen de ficit $(D_c),$ tine for max $D0$ defint $(t_c)$ and in

The Do level and $20CBO{D}_5$ of a sample taken $t$ the critical puit

$($Saturated sxygen comentration in sheam bafole discharge is $10\mathrm{.}07n\frac{g}{L}$

at $15C.$ Saturated $00$ at $15\mathrm{.}7C$ as $9\mathrm{.}9m\frac{g}{c}.$ Cse temp. crefficient of

$1\mathrm{.}135$ for $k_1$ and $1\mathrm{.}024$ for $k_2$ for appling temp. corrections for then two

constants.

$($s$)$ if effluent wator is not mixed $m$ stream water, what is the

maximum BOD concentration in effluent to meet the stream wath

OD stip. $[$itre for finding out resultant $DO,$BOD etc don't include

river water in calculation. Now we Do$-$ sag formule for calculating

minimum $DO$ in stream $=4m\frac{g}{L}$ asing afproach done earlies

for finding out maximum BOO in efflvent watur.