= It is intended to determine the characteristics of an activated sludge system (Aerobic biological treatment) for treating 10000 m/d of wastewater at a strength of 700 mg UBOD/L to a final UBOD concentration of 17.6 mg/L. It may be assumed that the mixed liquor VSS concentration (X) is 4300 mg/L, and the recycle ratio is 0.71. The following kinetic coefficients apply in this case: Um= 2.4 d-', ka = 0.05 d'", Ks =75 mg UBOD/L, Y = 0.42 mg VSS/mg UBOD. Determine: i) the mean cell time (SRT) in d, [5 marks] ii) the aeration basin volume (V) in m, [4 marks] iii) the solids production rate in reactor (Px) in kg/d, [4 marks] iv)the recycle solids concentration (XR) in mg/L and [8 marks] v) the sludge wastage rate (Qw) in mld. [4 marks]