Continuing the preparation of the proposal for the Waffle treatment plant ( Problem 3-15...

Continuing the preparation of the proposal for the Waffle treatment plant ( Problem 3-15 ), design the flocculation tank by providing the following for the first two compartments only:

1. Water power input in kW

2. Tank dimensions in m

3. Diameter of the impeller in m

4. Rotational speed of impeller in rpm

Use the following assumptions:

1. Number of tanks = 1 (with 1 backup)

2. Tapered G in three compartments: 60, 50, and 20 s ^–1

3. Detention time = 30 min

4. Depth = 3.5 m

5. Impeller type: axial-flow impeller, three blades, N_p = 0.43

6. Available impeller diameters: 1.0, 1.5, and 2.0 m

7. Assume B = (1/3) H

Problem 3-15

Your boss has assigned you the job of designing a rapid-mix tank for the new water treatment plant for the town of Waffle. The design flow rate is 0.050 m³ /s. The average water temperature is 8^oC. The following design assumptions for a rapid-mix tank have been made:

1. Number of tanks = 1 (with 1 backup)

2. Tank configuration: circular with liquid depth = 1.0 m

3. Detention time = 5 s

4. Velocity gradient = 750 s ^–1

5. Impeller type: turbine, 6 flat blades, N _p = 3.6

6. Available impeller diameters: 0.25, 0.50, and 1.0 m

7. Assume B = (1/3) H

Design the rapid-mix system by providing the following:

1. Water power input in kW

2. Tank dimensions in m

3. Diameter of the impeller in m

4. Rotational speed of impeller in rpm