A $15-mL$ sample is pipetted directly into a $300-mL$ incubation bottle. The initial $DO$ of the diluted

sample is $8\mathrm{.}4m\frac{g}{L},$ and its final DO after the $5-$day test is $1\mathrm{.}8m\frac{g}{L}.$ The seeded dilution water is

separately incubated in a $300-mL$ bottle for $5$ days, and the initial and final DO concentrations are,

respectively, $8\mathrm{.}8m\frac{g}{L}$ and $7\mathrm{.}5m\frac{g}{L}.$ After a long period of time, the sample DO is $0\mathrm{.}5m\frac{g}{L},$ and it

no longer seems to be dropping. The dilution water DO is reduced to $7\mathrm{.}0m\frac{g}{L}.$ Assume nitrification

has been inhibited so the only BOD being measured is carbonaceous.

a$.$ If the sample and the seeded dilution water are both incubated at $20C$ for $5$ days, what is the

$BO{D}_5$ of the sample?

b$.$ Assuming no nitrification effects, estimate the ultimate carbonaceous BOD $(L_0).$

c$.$ What would be the remaining BOD after five days have elapsed $(L_5)?$

d$.$ Estimate the deaeration reaction rate constant day $\{$:${?}^{-1}).$