A standard five$-$day BOD test is run using a mix consisting of $8$ parts distilled water and $2$ part wastewater $($no seed$).$ The initial DO of the mix is $9\mathrm{.}0$ mg$/$L$,$ and the DO$$after five days is determined to be $1\mathrm{.}0$ mg$/$L$.$ What is BOD$5?$

Question $1$Answer

$3\mathrm{.}2$ mg$/$L

$8$ mg$/$L

$40$ mg$/$L

$32$ mg$/$L