$(35$ points$).$ An activated sludge plant is

located at an elevation of $5,130-$ft$.$ The

maximum oxygen demand occurs in the

summer when the air temperature is $100F$

and the maximum wastewater temperature is

$82F.$ The oxygen demand is $14,213lbs.$

$\frac{O_2}{?}$ day. The airflow per diffuser is $15-$scfm

$($at $1-$atm and $20C),=0\mathrm{.}75,=0\mathrm{.}95,$ the

operating DO $=2\mathrm{.}0-m\frac{g}{L},$ the tank depth $=$

$15ft$ and the diffusers are $1\mathrm{.}5-ft$ above the

tank bottom. Determine:

$(15-pts)$ The oxygen transfer for the diffusers.

$(10-$pts$)$ The total airflow at the plant site;

$(10-$pts$)$ The total number of diffusers

required;