Waste water flow= 35000 m$^3$/day
Volume of aeration tank= 10900 m$^3$
Influent BOD= 250 mg/l
Effluent BOD= 20 mg/l
Mixed liquor suspended solids(MLSS)= 2500 mg/L
Effluent suspended solids= 30 mg/l
Waste sludge suspended solids= 9700 mg/l
Quality of waste sludge= 220 m$^3$/d
Based on the information above, determine:

• i) Aeration period (hours)
• ii) Food to micro-organisms ratio (F/M) (kg BOD per day/kg MLSS)
• iii) Percentage efficiency of BOD removal
• iv) Sludge age