Data from a field study on a step$-$aeration activated$-$sludge secondary treatment are as follows: Volume of

basin $=3,400m^3,$ settled wastewater flow $=13,900\frac{m^3}{?}$ day, return sludge flow $=4807\frac{m^3}{?}$ day, wasted

sludge flow $=71\mathrm{.}5\frac{m^3}{?}$ day, MLSS in aeration tank $=2350m\frac{g}{L},SS$ in waste sludge $=11,000m\frac{g}{L},$

influent wastewater BOD $=128m\frac{g}{L},$ effluent wastewater BOD $=22m\frac{g}{L},$ effluent $SS=26m\frac{g}{L}.$

Using these data, calculate: $(1)$ BOD removal efficiency, $(2)$ volumetric loading rate, $(3)$ food$-$to$-$

microorganisms ratio, $(4)$ detention time $($aeration period$),(5)$ mean cell residence time $($sludge age$),$ and

$(6)$ sludge production.