Page 13 9 Question 4: [25 marks] A high rate activated sludge process is being used to treat starch processing waste at a raw wastewater flow rate of 2000 m/d and an ultimate biological oxygen demand, UBOD of 640 mg/L. The kinetic coefficients are Hmax =1.2 d?, ka = 0.06 d', Ks=140 mg UBOD/L, Y=0.4 mg VSS/mg UBOD, and a process sludge age (Oc or SRT) of 2.25 d is being used. If the volume of the aeration basin is 175 m. and the solids are returned to the aeration basin (Q.) at a flow rate of 3600 m/d, determine: i) the residual (final) UBOD (S) in mg/L and the treatment efficiency, [4 marks] ii) the volatile suspended solids, YSS concentration in mg/L in the aeration basin (X), [2 marks] iii) the washout retention time (t) in d, [4 marks] iv) the volatile suspended solids, VSS production rate (Px) in kg/d, [3 marks] v) the volatile suspended solids, VSS concentration in mg/L in the recycle stream (X.), [5 marks] [3 marks] vi) the flow rate of the sludge wastage stream (Qw) in md and [4 marks] vii) the design oxygen supply (RO2V) in kg/d based on a 12% transfer efficiency