An activated sludge system (sketched below) is operating at equilibrium with the following information. Wastewater related data: flow rate $=500 \: m^3/hour$, influent BOD $= 150 mg/L$, effluent BOD $=10 \: mg/L$. Aeration tank related data: hydraulic retention time $=9$ hours, mean-cell-residence time $=240 $ hours, volume $4000 \: m^3$, mixed liquor suspended solids $ = 2000 \: mg/L$
The mass (in kg/day) of solids wasted from the system is
- $24000$
- $1000$
- $800$
- $33$