The following data pertains to an activated sludge treatment plant. Volume of aeration tank = 10000 m3, MLSS = 2900 mg/L, effluent suspended solids = 30 mg/l, waste sludge suspended solids = 8500 m/l, quantity of waste sludge = 150 m3/day, total sewage flow = 25000 m3/day. The sludge age in days is ___
1
10.24
2
11.43
3
12.71
4
14.35