(b) Two million litres of water per day is passing through a sedimentation tank which is 6m wide, 15m long and has a water depth of 3m. (i) Find the detention time for the tank. (4 marks) (ii) What is the average flow velocity through the tank ? (4 marks) (iii) If 60 ppm is the concentration of suspended solids in turbid raw water, how much dry solids will be deposited per day in the tank? Assume 80% removal in the tank and average specific gravity of the deposits as 2.0. (4 marks) (iv) Compute the overflow rate. (3 marks)