Question $2$:

A completely mixed high$-$rate activated sludge plant with recycling treats $18,000\frac{m^3}{?}$ day of industrial wastewater. The influent to the activated sludge reactor has a $BO{D}_5$ of $1050m\frac{g}{L}.$ It is desired to reduce the influent $BO{D}_5$ to $125m\frac{g}{L}$ prior to discharge to a municipal sewer. The mass of solid that needs to be wasted per day is $8000k\frac{g}{d}.$ Fine bubble membrane diffusers with total floor coverage are to be used for the aeration tank. The SOTR specified by the manufacturer is $3\mathrm{.}6kg\frac{O_2}{k}Wh,$ with $F$ of $0\mathrm{.}48.$ The average wastewater temperature is $18C.$ The residual DO in the aeration tank is $4\mathrm{.}2m\frac{g}{L},$ is $0\mathrm{.}90,$ the saturation oxygen concentration is $18C,$ and the tank depth elevation is $9\mathrm{.}54m\frac{g}{L}.$ Calculate the oxygen demand and the power required for aeration.